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  • 5901.
    Zhang, Jing
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för naturvetenskaplig biokemi.
    Biochemical Study and Technical Applications of Fungal Pectinase2006Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Pectinases are a group of enzymes produced by bacteria, fungi, higher plants and animals. Pectinases can modify and degrade pectins, a class of heterogeneous and multifunctional polysaccharides present in middle lamellae and primary cell walls of plants. Pectins have been showed to play diverse roles in cell physiology, growth, adhesion and separation. Pectinases are used technically in the processing of fiber production and fruit juice or wine making. We have studied the mechanisms and applications of pectinases, especially in retting, a microbiological process where bast fibers in flax and other bast fiber cultivars are released from each other and from the woody core.

    A strong correlation was found between the ability to perform retting and the degradation of sparsely esterified pectin, a substrate of polygalacturonase. This led to the conclusion that polygalacturonase plays a key role in the enzymatic retting of flax. We purified and characterized an extracellular polygalacturonase produced by Rhizopus oryzae, a very potent retting organism. The purified enzyme which appeared to be the single active component in retting, has non-methylated polygalacturonan as its preferred substrate. Peptide sequences indicate that the enzyme, like another polygalacturonase (EC. 3.2.1.15), belongs to glycosyl hydrolase family 28. It contains, however, an N-terminal sequence absent from other fungal pectinases, but present in an enzyme from the phytopathogenic bacterium, Ralstonia solanacearum.

    Our finding that removal of calcium ions from the plant material by pre-incubation in dilute acid in enzymatic retting could reduce enzyme consumption by several orders of magnitude, improves the economical feasibility of the enzymatic retting process. Comparisons with different acids showed that the action was mainly pH dependent.

    Pectinases were employed as analytical tools in a study of stored wood discoloration and, together with cellulases, in a mechanical process for making pulp from flax and hemp in paper production.

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  • 5902.
    Zhang, Jingji
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för cell- och molekylärbiologi, Struktur- och molekylärbiologi.
    Accuracy of mRNA Translation in Bacterial Protein Synthesis2015Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Reading of messenger RNA (mRNA) by aminoacyl-tRNAs (aa-tRNAs) on the ribosomes in the bacterial cell occurs with high accuracy. It follows from the physical chemistry of enzymatic reactions that there must be a trade-off between rate and accuracy of initial tRNA selection in protein synthesis: when the current accuracy, the A-value, approaches its maximal possible value, the d-value, the kinetic efficiency of the reaction approaches zero. We have used an in vitro system for mRNA translation with purified E. coli components to estimate the d- and A-values by which aa-tRNAs discriminate between their cognate and near cognate codons displayed in the ribosomal A site. In the case of tRNALys, we verified the prediction of a linear trade-off between kinetic efficiency of cognate codon reading and the accuracy of codon selection. These experiments have been extended to a larger set of tRNAs, including tRNAPhe, tRNAGlu, tRNAHis, tRNACys, tRNAAsp and tRNATyr, and linear efficiency-accuracy trade-off was observed in all cases. Similar to tRNALys, tRNAPhe discriminated with higher accuracy against a particular mismatch in the second than in the first codon position. Remarkably high d-values were observed for tRNAGlu discrimination against a C-C mismatch in the first codon position (70 000) and for tRNAPhe discrimination against an A-G mismatch in the second codon position (79 000). At the same time, we have found a remarkably small d-value (200) for tRNAGlu misreading G in the middle position of the codon (U-G mismatch).

    Aminoglycoside antibiotics induce large codon reading errors by tRNAs. We have studied the mechanism of aminoglycoside action and found that the drug stabilized aminoacyl-tRNA in a codon selective in relation to a codon non-selective state. This greatly enhanced the probability of near cognate aminoacyl-tRNAs to successfully transcend the initial selection step of the translating ribosome. We showed that Mg2+ ions, in contrast, favour codon non-selective states and thus induce errors in a principally different way than aminoglycosides. 

    We also designed experiments to estimate the overall accuracy of peptide bond formation with, including initial selection accuracy and proofreading of tRNAs after GTP hydrolysis on EF-Tu. Our experiments have now made it possible to calibrate the accuracy of tRNA selection in the test tube to that in the living cells. We will now also be able to investigate the degree to which the accuracy of tRNA selection has been optimized for maximal fitness.  

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  • 5903.
    Zhang, Jingji
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för cell- och molekylärbiologi, Struktur- och molekylärbiologi.
    Enhanced proofreading attenuates initial selection error hot spots in genetic code translation by transfer RNAsManuskript (preprint) (Annet vitenskapelig)
    Abstract [en]

    A system for cell free protein synthesis with E. coli components of high purity was used in conjunction with fast kinetics quench-flow measurements to characterize the accuracy of peptie bond formation by ribosomes with initiator tRNAfMet in P site and different codons in the A site. We used Glu-tRNAGlu, Lys-tRNALys and Phe-tRNAPhe in ternary complexes with EF-Tu and GTP to select ribosomes programmed with their respective cognate codons in competition with ribosomes containing near-cognate codons. Variation of the free Mg2+ concentration in the in vitro buffer system was used to calibrate its accuracy to that of codon selection by Glu-tRNAGlu in living E. coli cells, previously estimated from the residual activity of a beta-galactosidase mutant in which the codon for an essential Glu had been altered to near cognate codons. At 2.3 mM free Mg2+ concentration, the accuracy in the living cell agreed with that in the test tube, a feature making our biochemistry directly relevant to bacterial physiology. We found that the total accuracy of tRNA selection varied by five orders of magnitude depending on the type of tRNA, type of mismatch and mismatched codon position. We partitioned the total accuracy into initial selection of ternary complex before GTP hydrolysis on EF-Tu and proofreading selection of aminoacyl-tRNA after GTP hydrolysis. We found the contribution of proofreading to be strongly positively correlated with the accuracy of initial selection in its high range. As initial selection decreased further the proofreading contribution to accuracy increased, rather than decreased, a feature neutralizing potentially disastrous missense error hot spots associated with, in particular, tRNAGlu.    

  • 5904.
    Zhang, Jingji
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för cell- och molekylärbiologi, Struktur- och molekylärbiologi.
    On the mechanism of translation error induction by aminoglycoside antibioticsManuskript (preprint) (Annet vitenskapelig)
    Abstract [en]

    We used a cell-free system with pure Escherichia coli components to study how the aminoglycosides disrupt initial codon selection of aminoacyl-tRNAs in ternary complex with elongation factor Tu and GTP by messenger RNA-programmed ribosomes. We take the advantage of the universal rate-accuracy trade-off for all enzymatic selections to determine how the efficiency of initial codon readings decreased linearly toward zero as the accuracy of discrimination against near cognate and wobble codon readings increased toward the maximal asymptote, the effective d value. It turns out two ribosome bound states of ternary complex. First, one codon non-selective step, Mg2+ ions shift the equilibrium from free to ribosome bound ternary complex meaning that the equilibrium between the two ribosome bound complexes is unaltered. Second, codon selective step, aminoglycosides shift the equilibrium from codon non-selective to codon selective complex meaning that the equilibrium between the free and the codon non-selective state is unchanged.

  • 5905.
    Zhang, Jingji
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för cell- och molekylärbiologi, Struktur- och molekylärbiologi.
    Ieong, Ka-Weng
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för cell- och molekylärbiologi, Struktur- och molekylärbiologi.
    Johansson, Magnus
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för cell- och molekylärbiologi, Struktur- och molekylärbiologi. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för cell- och molekylärbiologi, Beräknings- och systembiologi.
    Ehrenberg, Måns
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för cell- och molekylärbiologi, Struktur- och molekylärbiologi.
    Large accuracy variation in initial codon selection by aminoacyl-tRNAs on the bacterial ribosomeManuskript (preprint) (Annet vitenskapelig)
  • 5906.
    Zhang, Jingji
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för cell- och molekylärbiologi.
    Pavlov, Michael
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för cell- och molekylärbiologi, Molekylärbiologi.
    Ehrenberg, Måns
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för cell- och molekylärbiologi, Molekylärbiologi.
    Accuracy of genetic code translation and its orthogonal corruption by aminoglycosides and Mg2+ ions2018Inngår i: Nucleic Acids Research, ISSN 0305-1048, E-ISSN 1362-4962, Vol. 46, nr 3, s. 1362-1374Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We studied the effects of aminoglycosides and changing Mg2+ ion concentration on the accuracy of initial codon selection by aminoacyl-tRNA in ternary complex with elongation factor Tu and GTP (T-3) on mRNA programmed ribosomes. Aminoglycosides decrease the accuracy by changing the equilibrium constants of 'monitoring bases' A1492, A1493 and G530 in 16S rRNA in favor of their 'activated' state by large, aminoglycoside-specific factors, which are the same for cognate and near-cognate codons. Increasing Mg2+ concentration decreases the accuracy by slowing dissociation of T-3 from its initial codon-and aminoglycoside-independent binding state on the ribosome. The distinct accuracy-corrupting mechanisms for aminoglycosides and Mg2+ ions prompted us to re-interpret previous biochemical experiments and functional implications of existing high resolution ribosome structures. We estimate the upper thermodynamic limit to the accuracy, the 'intrinsic selectivity' of the ribosome. We conclude that aminoglycosides do not alter the intrinsic selectivity but reduce the fraction of it that is expressed as the accuracy of initial selection. We suggest that induced fit increases the accuracy and speed of codon reading at unaltered intrinsic selectivity of the ribosome.

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  • 5907.
    Zhang, Li
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för cell- och molekylärbiologi, Struktur- och molekylärbiologi.
    Jiang, Wangshu
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för cell- och molekylärbiologi, Struktur- och molekylärbiologi.
    Nan, Jie
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för cell- och molekylärbiologi.
    Almqvist, Jonas
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för cell- och molekylärbiologi, Struktur- och molekylärbiologi.
    Huang, Yafei
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för cell- och molekylärbiologi.
    The Escherichia coli CysZ is a pH dependent sulfate transporter that can be inhibited by sulfite2014Inngår i: Biochimica et Biophysica Acta - Biomembranes, ISSN 0005-2736, E-ISSN 1879-2642, Vol. 1838, nr 7, s. 1809-1816Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The Escherichia coli inner membrane protein CysZ mediates the sulfate uptake subsequently utilized for the synthesis of sulfur-containing compounds in cells. Here we report the purification and functional characterization of CysZ. Using Isothermal Titration Calorimetry, we have observed interactions between CysZ and its putative substrate sulfate. Additional sulfur-containing compounds from the cysteine synthesis pathway have also been analyzed for their abilities to interact with CysZ. Our results suggest that CysZ is dedicated to a specific pathway that assimilates sulfate for the synthesis of cysteine. Sulfate uptake via CysZ into E. coil whole cells and proteoliposome offers direct evidence of CysZ being able to mediate sulfate uptake. In addition, the cysteine synthesis pathway intermediate sulfite can interact directly with CysZ with higher affinity than sulfate. The sulfate transport activity is inhibited in the presence of sulfite, suggesting the existence of a feedback inhibition mechanism in which sulfite regulates sulfate uptake by CysZ. Sulfate uptake assays performed at different extracellular pH and in the presence of a proton uncoupler indicate that this uptake is driven by the proton gradient. (C) 2014 Elsevier B.V. All rights reserved.

  • 5908. Zhang, Liang
    et al.
    Fontana, Jacopo
    Bernhem, Kristoffer
    Nilsson, Linnéa
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biofysik.
    Scott, Lena
    Blom, Hans
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biofysik.
    Brismar, Hjalmar
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biofysik.
    Aperia, Anita
    Ouabain intervenes early in the apoptotic process by preventing BAD activationManuskript (preprint) (Annet vitenskapelig)
  • 5909. Zhang, Lifang
    et al.
    Carlberg, Inger
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för biokemi och biofysik.
    Norling, Birgitta
    Deletion of Synechocystis sp PCC 6803 Leader Peptidase LepB1 Affects Photosynthetic Complexes and Respiration2013Inngår i: Molecular & Cellular Proteomics, ISSN 1535-9476, E-ISSN 1535-9484, Vol. 12, nr 5, s. 1192-1203Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The cyanobacterium Synechocystis sp. PCC 6803 possesses two leader peptidases, LepB1 (SII0716) and LepB2 (SIr1377), responsible for the processing of signal peptide-containing proteins. Deletion of the gene for LepB1 results in an inability to grow photoautotrophically and an extreme light sensitivity. Here we show, using a combination of Blue Native/SDS-PAGE, Western blotting and iTRAQ analysis, that lack of LepB1 strongly affects the cell's ability to accumulate wild-type levels of both photosystem I (PSI) and cytochrome (Cyt) b(6)f complexes. The impaired assembly of PSI and Cyt b(6)f is considered to be caused by the no or slow processing of the integral subunits PsaF and Cyt f respectively. In particular, PsaF, one of the PSI subunits, was found incorporated into PSI in its unprocessed form, which could influence the assembly and/or stability of PSI. In contrast to these results, we found the amount of assembled photosystem II (PSII) unchanged, despite a slower processing of PsbO. Thus, imbalance in the ratios of PSI and Cyt b(6)f to photosystem II leads to an imbalanced photosynthetic electron flow up- and down-stream of the plastoquinone pool, resulting in the observed light sensitivity of the mutant. We conclude that LepB1 is the natural leader peptidase for PsaF, PsbO, and Cyt f. The maturation of PsbO and Cyt f can be partially performed by LepB2, whereas PsaF processing is completely dependent on LepB1. iTRAQ analysis also revealed a number of indirect effects accompanying the mutation, primarily a strong induction of the CydAB oxidase as well as a significant decrease in phycobiliproteins and chlorophyll/heme biosynthesis enzymes.

  • 5910.
    Zhang, Lu
    et al.
    Uppsala universitet, Medicinska och farmaceutiska vetenskapsområdet, Medicinska fakulteten, Institutionen för medicinsk biokemi och mikrobiologi.
    Ding, Zhoujie
    Uppsala universitet, Medicinska och farmaceutiska vetenskapsområdet, Medicinska fakulteten, Institutionen för medicinsk biokemi och mikrobiologi.
    Xu, Hui
    Uppsala universitet, Medicinska och farmaceutiska vetenskapsområdet, Medicinska fakulteten, Institutionen för medicinsk biokemi och mikrobiologi.
    Heyman, Birgitta
    Uppsala universitet, Medicinska och farmaceutiska vetenskapsområdet, Medicinska fakulteten, Institutionen för medicinsk biokemi och mikrobiologi.
    Marginal-zone B cells transport IgG3-antigen immune complexes into splenic B cell follicles2014Inngår i: Molecular Immunology, ISSN 0161-5890, E-ISSN 1872-9142, Vol. 61, nr 2, s. 278-278Artikkel i tidsskrift (Annet vitenskapelig)
  • 5911. Zhang, Peng
    et al.
    Chen, Lin
    Zhang, Qingsong
    Jönsson, Leif J.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Hong, Feng F.
    Using in situ nanocellulose-coating technology based on dynamic bacterial cultures for upgrading conventional biomedical materials and reinforcing nanocellulose hydrogels2016Inngår i: Biotechnology progress (Print), ISSN 8756-7938, E-ISSN 1520-6033, Vol. 32, nr 4, s. 1077-1084Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Bacterial nanocellulose (BNC) is a microbial nanofibrillar hydrogel with many potential applications. Its use is largely restricted by insufficient strength when in a highly swollen state and by inefficient production using static cultivation. In this study, an in situ nanocellulose-coating technology created a fabric-frame reinforced nanocomposite of BNC hydrogel with superior strength but retained BNC native attributes. By using the proposed technology, production time could be reduced from 10 to 3 days to obtain a desirable hydrogel sheet with approximately the same thickness. This novel technology is easier to scale up and is more suitable for industrial-scale manufacture. The mechanical properties (tensile strength, suture retention strength) and gel characteristics (water holding, absorption and wicking ability) of the fabric-reinforced BNC hydrogel were investigated and compared with those of ordinary BNC hydrogel sheets. The results reveal that the fabric-reinforced BNC hydrogel was equivalent with regard to gel characteristics, and exhibited a qualitative improvement with regard to its mechanical properties. For more advanced applications, coating technology via dynamic bacterial cultures could be used to upgrade conventional biomedical fabrics, i.e. medical cotton gauze or other mesh materials, with nanocellulose.

  • 5912. Zhang, Qi
    et al.
    Wang, Guangji
    Du, Yu
    Zhu, Lingling
    Jiye, A
    Umeå universitet, Medicinska fakulteten, Institutionen för medicinsk biovetenskap, Klinisk kemi.
    GC/MS analysis of the rat urine for metabonomic research2007Inngår i: Journal of chromatography. B, ISSN 1570-0232, E-ISSN 1873-376X, Vol. 854, nr 1-2, s. 20-25Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In this paper, an optimized protocol was established and validated for the metabonomic profiling in rat urine using GC/MS. The urine samples were extracted by methanol after treatment with urease to remove excessive urea, then the resulted supernatant was dried, methoximated, trimethylsilylated, and analyzed by GC/MS. Forty-nine endogenous metabolites were separated and identified in GC/MS chromatogram, of which 26 identified compounds were selected for quantitative analysis to evaluate the linearity, precision, and sensitivity of the method. It showed good linearity between mass spectrometry responses and relative concentrations of the 26 endogenous compounds over the range from 0.063 to 1.000(v/v, urine/urine+ water) and satisfactory reproducibility with intra-day and inter-days precision values all below 15%. The metabonomic profiling method based on GC/MS was successfully applied to urine samples from hyperlipidemia model rats. Obviously, separated clustering of model rats and the control rats were shown by principal components analysis (PCA); time-dependent metabonomic modification was detected as well. It was suggested that metabonomic profiling based on GC/MS be a robust method for urine samples.

  • 5913.
    Zhang, Qiong
    KTH, Skolan för bioteknologi (BIO), Teoretisk kemi och biologi.
    Molecular Dynamics Simulations of Biomimetic Carbohydrate Materials2011Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    The present thesis honors contemporary molecular dynamics simulation methodologies which provide powerful means to predict data, interpret observations and widen our understanding of the dynamics, structures and interactions of carbohydrate systems. With this as starting point my thesis work embarked on several cutting edge problems summarized as follows.

    In my first work the thermal response in crystal cellulose Iβ was studied with special emphasis on the temperature dependence of the crystal unit cell parameters and the organization of the hydrogen bonding network. The favorable comparison with available experimental data, like the phase transition temperature, the X-ray diffraction crystal structures of cellulose Iβ at room and high temperatures, and temperature dependent IR spectra supported our conclusions on the good performance of the GLYCAM06 force field for the description of cellulose crystals, and that a cautious parameterization of the non-bonded interaction terms in a force field is critical for the correct prediction of the thermal response in cellulose crystals.

    The adsorption properties of xyloglucans on the cellulose Iβ surface were investigated in my second paper. In our simulations, the interaction energies between xyloglucan and cellulose in water were found to be considerably lower than those in vacuo. The van der Waals interactions played a prevailing role over the electrostatic interactions in the adsorption. Though the variation in one side chain did not have much influence on the interaction energy and the binding affinity, it did affect the structural properties of the adsorbed xyloglucans.

    The interaction of the tetradecasaccharide XXXGXXXG in complex with the hybrid aspen xyloglucan endo-transglycosylase PttXET16-34 was studied in the third paper. The effect of the charge state of the “nucleophile helper” residue Asp87 on the PttXET16-34 active site structure was emphasized. The results indicate that the catalysis is optimal when the catalytic nucleophile is deprotonated, while the “helper” residue and general acid/base residue are both protonated.

    In my forth paper, the working mechanism for a redox-responsive bistable [2]rotaxane based on an α-cyclodextrin ring was investigated. The umbrella sampling technique was employed to calculate the free energy profiles for the shuttling motion of the α-cyclodextrin ring between two recognition sites on the dumbbell of the rotaxane. The calculated free energy profiles verified the binding preferences observed experimentally. The driving force for the shuttling movement of the α-cyclodextrin ring was revealed by the analysis of the free energy components.

    Fulltekst (pdf)
    PhD_thesis_KTH_qiongzhang
  • 5914.
    Zhang, Qiong
    et al.
    KTH, Skolan för bioteknologi (BIO), Teoretisk kemi och biologi.
    Brumer, Harry
    KTH, Skolan för bioteknologi (BIO), Glykovetenskap.
    Ågren, Hans
    KTH, Skolan för bioteknologi (BIO), Teoretisk kemi och biologi.
    Tu, Yaoquan
    KTH, Skolan för bioteknologi (BIO), Teoretisk kemi och biologi.
    The adsorption of xyloglucan on cellulose: effects of explicit water and side chain variation2011Inngår i: Carbohydrate Research, ISSN 0008-6215, E-ISSN 1873-426X, Vol. 346, nr 16, s. 2595-2602Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The interaction between para-crystalline cellulose and the cross-linking glycan xyloglucan (XG) plays a central role for the strength and extensibility of plant cell walls. The coating of XGs on cellulose surfaces is believed to be one of the most probable interaction patterns. In this work, the effects of explicit water and side chain variation on the adsorption of XGs on cellulose are investigated by means of atomistic molecular dynamics simulations. The adsorption properties are studied in detail for three XGs on cellulose I beta 1-10 surface in aqueous environment, namely GXXXGXXXG, GXXLGXXXG, and GXXFGXXXG, which differ in the length and composition of one side chain. Our work shows that when water molecules are included in the theoretical model, the total interaction energies between the adsorbed XGs and cellulose are considerably smaller than in vacuo. Furthermore, in water environment the van der Waals interactions prevail over the electrostatic interactions in the adsorption. Variation in one side chain does not have significant influence on the interaction energy and the binding affinity, but does affect the equilibrium structural properties of the adsorbed XGs to facilitate the interaction between both the backbone and the side chain residues with the cellulose surface. Together, this analysis provides new insights into the nature of the XG-cellulose interaction, which helps to further refine current molecular models of the composite plant cell wall.

  • 5915.
    Zhang, Rong
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för naturvetenskaplig biokemi.
    New approaches to concentration, desalting and separation of biopolymers in capillary electrophoresis1997Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    In the first part of the thesis five new on-tube methods for concentration and desalting ofampholytes, such as peptides and proteins, are described in Papers I and II. The methods arebased on the fact that electrophoretic migration velocities decrease upon a decrease in theabsolute value of the zeta potential of a solute and the pore size of the electrophoresis mediumand upon an increase in the cross section of the electrophoresis chamber, the viscosity and theelectrical conductivity of the electrophoresis medium. A combination of displacementelectrophoresis and a hydrodynamic counter flow is also utilized to create a stationary zone inwhich the sample solute can be concentrated continuously. Paper III describes an on-tubedesalting technique for IEF, which is based on an automatic substitution of the salts in thesample with an ampholyte solution in a short focusing pre-step. A simple off-tubeconcentration and desalting method using a hollow fiber is described in Paper IV, which isbased on the transport of water by evaporation or the Donnan effect out of the fiber throughthe pores in its wall and has the advantage that solute adsorption is negligible. The method canbe used not only for macromolecules but also for low-molecular-weight compounds.

    The second part of thesis consists of two publications about HPCE in the presence ofadditives. In Paper V liposomes were used as a pseudostationary phase in CZE. The decreasein the mobility of an analyte owing to the presence of liposomes reflected interaction betweenanalytes and liposomes. Paper VI deals with the shifts in mobilities of peptides and proteinswhen buffers are supplemented with β-cyclodextrin sulfate and 6-amino β-cyclodextrin. A newdefinition of resolution of two very adjacent peaks, without knowing peak widths, is suggested.

    Studies of crystals of lysozyme and MBP by HPCE were presented in the last part of thethesis (Paper VII), which show that HPCE can be used to shed some light on the question whysome protein crystals afford low resolution upon X-ray diffraction.

  • 5916.
    Zhang, Rui
    et al.
    Beijing Univ Chem Technol, Coll Life Sci & Technol, Beijing Key Lab Bioproc, North Third Ring Rd 15, Beijing 100029, Peoples R China.
    Zhang, Tianji
    Natl Inst Metrol, Div Chem & Analyt Sci, Beijing, Peoples R China.
    Lv, Yongqin
    Beijing Univ Chem Technol, Coll Life Sci & Technol, Beijing Key Lab Bioproc, North Third Ring Rd 15, Beijing 100029, Peoples R China.
    Qin, Peiyong
    Beijing Univ Chem Technol, Coll Life Sci & Technol, Beijing Key Lab Bioproc, North Third Ring Rd 15, Beijing 100029, Peoples R China.
    Li, Hongmei
    Natl Inst Metrol, Div Chem & Analyt Sci, Beijing, Peoples R China.
    Li, Jin-Ping
    Uppsala universitet, Medicinska och farmaceutiska vetenskapsområdet, Medicinska fakulteten, Institutionen för medicinsk biokemi och mikrobiologi. Beijing Univ Chem Technol, Int Res Ctr Soft Matter, Beijing, Peoples R China.
    Tan, Tianwei
    Beijing Univ Chem Technol, Coll Life Sci & Technol, Beijing Key Lab Bioproc, North Third Ring Rd 15, Beijing 100029, Peoples R China.
    Selective binding of heparin oligosaccharides in a magnetic thermoresponsive molecularly imprinted polymer2019Inngår i: Talanta: The International Journal of Pure and Applied Analytical Chemistry, ISSN 0039-9140, E-ISSN 1873-3573, Vol. 201, s. 441-449Artikkel, forskningsoversikt (Fagfellevurdert)
    Abstract [en]

    Heparin is a highly sulfated polysaccharide, applied in clinic for treatment of thrombotic diseases. The biological activity is closely related to its molecular structure e.g. compositions of disaccharides and oligosaccharides units. The classical method to isolate the oligosaccharides after depolymerization by heparinases or nitrous acid I s by size exclusion chromatography which is a time-consuming process. In this study, we explored the possibility for rapid separation of oligosaccharides using a novel polymer material. The magnetic thermoresponsive molecularly imprinted polymers (MIPs) were synthesized using heparin disaccharide as a template, AEM, NIPAAm, and AAm as functional monomer, and MBAA as crosslinker by surface radical polymerization in an aqueous media. Incubation of the MIP with hepairn oligosaccharides demonstrated specific binding to the template molecule. This binding to the targeted molecule was affected by reaction temperature with regard to binding capacity and specificity. The recognition specificity and selectivity can be modulated by varying the compositions of multifunctional monomers. The pseudo-second-order kinetic model and Langmuir isotherm model provide the best fit to the equilibrium adsorption of heparin disaccharides by MIPs. The results suggest that the new material can be used for rapid separation of di- and tetra-saccharides of heparin, which can also be adapted to the applications for isolation of oligosaccharides from other polysaccharides, e.g. heparan sulfate and chondoriting sulfate.

  • 5917.
    Zhang, Shouting
    Uppsala universitet, Medicinska vetenskapsområdet, Medicinska fakulteten, Institutionen för medicinsk biokemi och mikrobiologi.
    Studies on the Molecular Biology of the Mouse Pneumotropic Polyomavirus2003Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    The Murine Pneumotropic Virus (MPtV), in contrast to the other MurinePolyomavirus (MPyV), appears to be non-tumourigenic in its natural host. Instead, MPtV causes acute pneumonia and can serve as a model in studies of polyomavirus-induced disease. In initial experiments, MPtV large T-antigen (LT) was expressed in a heterologous system. LT was characterized with regard to its metabolic stability and cell immortalizing activity and, after purification, to its specific DNA binding.

    The absence of permissive cell culture system for MPtV has hampered its study. We made attempts to widen the host range of the virus by modifying the regulatory and late regions of the genome. The enhancer substitution mutant (KVm1), having a transcriptional enhancer substituted with a corresponding DNA segment from MPyV, was able to replicate in mouse 3T3 cells and form virus particles that were infectious in mice. However, efficient infection of cells in vitro was not achieved with this mutant virus, possibly due to the absence of virus-specific receptors on the cells. The capsid protein substitution mutants, having capsid protein genes of MPyV, for which receptors are present on a variety of cell types, showed also no cytopathic effect, despite an enhanced viral DNA replication and assembly of virus particles.

    MPtV-DNA extracted from virus in lung tissue of infected mice had a heterogeneous enhancer segment. A majority of the DNA molecules had a structure differing from the standard-type. A 220 base-pair insertion at nucleotide position 142 with a concomitant deletion of nucleotides 143 to 148 was a prominent variation. Other genome variants showed complete or partial deletions of the insertion and surrounding sequences in the viral enhancer. In relation to the standard-type, all variant genomes showed differences in the activities of transcriptional promoters and the origin DNA replication. Analysis by DNA reassociation showed that a large number of nucleotide sequences related to the 220 base-pair insert in the MPtV genome were present in mouse and human DNA, but not in Escherichia coli DNA. Together, the data suggest that the 220 base-pair insertion is related to a transposable element of a novel type.

    Fulltekst (pdf)
    FULLTEXT01
  • 5918. Zhang, Shuo
    et al.
    Winestrand, Sandra
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Guo, Xiang
    Chen, Lin
    Hong, Feng
    Jönsson, Leif
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Effects of aromatic compounds on the production of bacterial nanocellulose by Gluconacetobacter xylinus2014Inngår i: Microbial Cell Factories, ISSN 1475-2859, E-ISSN 1475-2859, Vol. 13, s. 62-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Background:

    Bacterial cellulose (BC) is a polymeric nanostructured fibrillar network produced by certain microorganisms, principally Gluconacetobacter xylinus. BC has a great potential of application in many fields. Lignocellulosic biomass has been investigated as a cost-effective feedstock for BC production through pretreatment and hydrolysis. It is well known that detoxification of lignocellulosic hydrolysates may be required to achieve efficient production of BC. Recent results suggest that phenolic compounds contribute to the inhibition of G. xylinus. However, very little is known about the effect on G. xylinus of specific lignocellulose-derived inhibitors. In this study, the inhibitory effects of four phenolic model compounds (coniferyl aldehyde, ferulic acid, vanillin and 4-hydroxybenzoic acid) on the growth of G. xylinus, the pH of the culture medium, and the production of BC were investigated in detail. The stability of the phenolics in the bacterial cultures was investigated and the main bioconversion products were identified and quantified.

    Results:

    Coniferyl aldehyde was the most potent inhibitor, followed by vanillin, ferulic acid, and 4-hydroxybenzoic acid. There was no BC produced even with coniferyl aldehyde concentrations as low as 2 mM. Vanillin displayed a negative effect on the bacteria and when the vanillin concentration was raised to 2.5 mM the volumetric yield of BC decreased to similar to 40% of that obtained in control medium without inhibitors. The phenolic acids, ferulic acid and 4-hydroxybenzoic acid, showed almost no toxic effects when less than 2.5 mM. The bacterial cultures oxidized coniferyl aldehyde to ferulic acid with a yield of up to 81%. Vanillin was reduced to vanillyl alcohol with a yield of up to 80%.

    Conclusions:

    This is the first investigation of the effect of specific phenolics on the production of BC by G. xylinus, and is also the first demonstration of the ability of G. xylinus to convert phenolic compounds. This study gives a better understanding of how phenolic compounds and G. xylinus cultures are affected by each other. Investigations in this area are useful for elucidating the mechanism behind inhibition of G. xylinus in lignocellulosic hydrolysates and for understanding how production of BC using lignocellulosic feedstocks can be performed in an efficient way.

    Fulltekst (pdf)
    fulltext
  • 5919. Zhang, Sicai
    et al.
    Berntsson, Ronnie P. A.
    Umeå universitet, Medicinska fakulteten, Institutionen för medicinsk kemi och biofysik. Stockholm Univ, Dept Biochem & Biophys, SE-10691 Stockholm, Sweden.
    Tepp, William H.
    Tao, Liang
    Johnson, Eric A.
    Stenmark, Pal
    Dong, Min
    Structural basis for the unique ganglioside and cell membrane recognition mechanism of botulinum neurotoxin DC2017Inngår i: Nature Communications, ISSN 2041-1723, E-ISSN 2041-1723, Vol. 8, artikkel-id 1637Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Botulinum neurotoxins (BoNTs), the most potent toxins known, are potential bioterrorism agents. It is well established that all seven serotypes of BoNTs (BoNT/A-G) require complex gangliosides as co-receptors. Here, we report that BoNT/DC, a presumed mosaic toxin between BoNT/D and BoNT/C1, binds and enters efficiently into neurons lacking complex gangliosides and shows no reduction in toxicity in mice deficient in complex gangliosides. The co-crystal structure of BoNT/DC with sialyl-Thomsen-Friedenreich antigen (Sialyl-T) suggests that BoNT/DC recognizes only the sialic acid, but not other moieties in gangliosides. Using liposome flotation assays, we demonstrate that an extended loop in BoNT/DC directly interacts with lipid membranes, and the co-occurring sialic acid binding and loop-membrane interactions mediate the recognition of gangliosides in membranes by BoNT/DC. These findings reveal a unique mechanism for cell membrane recognition and demonstrate that BoNT/DC can use a broad range of sialic acid-containing moieties as co-receptors.

    Fulltekst (pdf)
    fulltext
  • 5920.
    Zhang, Sicai
    et al.
    Harvard Med Sch, USA.
    Masuyer, Geoffrey
    Stockholm University.
    Zhang, Jie
    Harvard Med Sch, USA.
    Shen, Yi
    Harvard Med Sch, USA.
    Lundin, Daniel
    Stockholm University.
    Henriksson, Linda
    Stockholm University.
    Miyashita, Shin-Ichiro
    Harvard Med Sch, USA.
    Martinez-Carranza, Markel
    Stockholm University.
    Dong, Min
    Harvard Med Sch, USA.
    Stenmark, Pål
    Stockholm University.
    Identification and characterization of a novel botulinum neurotoxin2017Inngår i: Nature Communications, ISSN 2041-1723, E-ISSN 2041-1723, Vol. 8, artikkel-id 14130Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Botulinum neurotoxins are known to have seven serotypes (BoNT/A-G). Here we report a new BoNT serotype, tentatively named BoNT/X, which has the lowest sequence identity with other BoNTs and is not recognized by antisera against known BoNTs. Similar to BoNT/B/D/F/G, BoNT/X cleaves vesicle-associated membrane proteins (VAMP) 1, 2 and 3, but at a novel site (Arg66-Ala67 in VAMP2). Remarkably, BoNT/X is the only toxin that also cleaves non-canonical substrates VAMP4, VAMP5 and Ykt6. To validate its activity, a small amount of full-length BoNT/X was assembled by linking two non-toxic fragments using a transpeptidase (sortase). Assembled BoNT/X cleaves VAMP2 and VAMP4 in cultured neurons and causes flaccid paralysis in mice. Thus, BoNT/X is a novel BoNT with a unique substrate profile. Its discovery posts a challenge to develop effective countermeasures, provides a novel tool for studying intracellular membrane trafficking, and presents a new potential therapeutic toxin for modulating secretions in cells.

    Fulltekst (pdf)
    fulltext
  • 5921.
    Zhang, Wei
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för biokemi och organisk kemi, Biokemi.
    Directed Evolution of Glutathione Transferases with Altered Substrate Selectivity Profiles: A Laboratory Evolution Study Shedding Light on the Multidimensional Nature of Epistasis2011Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Directed evolution is generally regarded as a useful approach in protein engineering. By subjecting members of a mutant library to the power of Darwinian evolution, desired protein properties are obtained. Numerous reports have appeared in the literature showing the success of tailoring proteins for various applications by this method. Is it a one-way track that protein practitioners can only learn from nature to enable more efficient protein engineering?

    A structure-and-mechanism-based approach, supplemented with the use of reduced amino acid alphabets, was proposed as a general means for semi-rational enzyme engineering. Using human GST A2-2*E, the most active human enzyme in the bioactivation of azathioprine, as a parental enzyme to test this approach, a L107G/L108D/F222H triple-point mutant of GST A2-2*E (thereafter designated as GDH) was discovered with 70-fold increased activity, approaching the upper limit of specific activity of the GST scaffold. The approach was further experimentally verified to be more successful than intuitively choosing active-site residues in proximity to the bound substrate for the improvement of enzyme performance.

    By constructing all intermediates along all putative mutational paths leading from GST A2-2*E to mutant GDH and assaying them with nine alternative substrates, the fitness landscapes were found to be “rugged” in differential fashions in substrate-activity space. The multidimensional fitness landscapes stemming from functional promiscuity can lead to alternative outcomes with enzymes optimized for other features than the selectable markers that were relevant at the origin of the evolutionary process. The results in this thesis suggest that in this manner an evolutionary response to changing environmental conditions can readily be mounted.

    In summary, the thesis demonstrates the attractive features of the structure-and-mechanism-based semi-rational directed evolution approach for optimizing enzyme performance. Moreover, the results gained from the studies show that laboratory evolution may refine our understanding of evolutionary process in nature.

    Fulltekst (pdf)
    fulltext
  • 5922.
    Zhang, Wei
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - BMC, Biokemi.
    Dourado, Daniel F. A. R.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - BMC, Biokemi.
    Fernandes, Pedro
    Universidade do Porto Rua do Campo Alegre.
    Ramos, Maria
    Universidade do Porto Rua do Campo Alegre.
    Mannervik, Bengt
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - BMC, Biokemi.
    Multidimensional epistasis and fitness landscapes in enzyme evolution2012Inngår i: Biochemical Journal, ISSN 0264-6021, E-ISSN 1470-8728, Vol. 445, s. 39-46Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The conventional analysis of enzyme evolution is to regard one single salient feature as a measure of fitness, expressed in a milieu exposing the possible selective advantage at a given time and location. Given that a single protein may serve more than one function, fitness should be assessed in several dimensions. In the present study we have explored individual mutational steps leading to a triple-point-mutated human GST (glutathione transferase) A2-2 displaying enhanced activity with azathioprine. A total of eight alternative substrates were used to monitor the diverse evolutionary trajectories. The epistatic effects of the imitations on catalytic activity were variable in sign and magnitude and depended on the substrate used, showing that epistasis is a multidimensional quality. Evidently, the multidimensional fitness landscape can lead to alternative trajectories resulting in enzymes optimized for features other than the selectable markers relevant at the origin of the evolutionary process. In this manner the evolutionary response is robust and can adapt to changing environmental conditions.

  • 5923.
    Zhang, Wei
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - BMC.
    Dourado, Daniel F. A. R.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för cell- och molekylärbiologi, Beräknings- och systembiologi.
    Mannervik, Bengt
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - BMC, Biokemi.
    Evolution of the active site of human glutathione transferase A2-2 for enhanced activity with dietary isothiocyanates2015Inngår i: Biochimica et Biophysica Acta - General Subjects, ISSN 0304-4165, E-ISSN 1872-8006, Vol. 1850, nr 4, s. 742-749Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Background: Organic isothiocyanates (ITCs) are produced by plants, in which they are released from glucosinolates by myrosinase. ITCs are generally toxic and serve as a chemical defense against herbivorous insects and against infections by microorganisms. In mammalian tissues subtoxic concentrations of ITCs can provide protective effects against cancer and other diseases partially by induction of glutathione transferases (GSTs) and other detoxication enzymes. Thus, human consumption of edible plants rich in ITCs is presumed to provide health benefits. ITCs react with intracellular glutathione to form dithiocarbamates, catalyzed by GSTs. Formation of glutathione conjugates is central to the biotransformation of ITCs and leads to a route for their excretion. Clearly, the emergence of ITC conjugating activity in GSTs is essential from the biological and evolutionary perspective. Methods: In the present investigation an active-site-focused mutant library of GST A2-2 has been screened for enzyme variants with enhanced ITC activity. Results: Significantly superior activities were found in 34 of the approximately 2000 mutants analyzed, and the majority of the superior GSTs featured His and Gly residues in one of the three active-site positions subjected to mutagenesis. Conclusions: We explored the propensity of GSTs to obtain altered substrate selectivity and moreover, identified a specific pattern of mutagenesis in GST for enhanced PEITC detoxification, which may play an important role in the evolution of adaptive responses in organisms subjected to ITCs. General significance: The facile acquisition of enhanced ITC activity demonstrates that this important detoxication function can be promoted by numerous evolutionary trajectories in sequence space. (C) 2014 Elsevier B.V. All rights reserved.

  • 5924.
    Zhang, Wei
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för biokemi och organisk kemi.
    Modén, Olof
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för biokemi och organisk kemi.
    Mannervik, Bengt
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för biokemi och organisk kemi.
    Differences among allelic variants of human glutathione transferase A2-2 in the activation of azathioprine2010Inngår i: Chemico-Biological Interactions, ISSN 0009-2797, E-ISSN 1872-7786, Vol. 186, nr 2, s. 110-117Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Azathioprine has been clinically used for decades in connection with organ transplantation, autoimmune disease, and treatment of cancer. Toxic side-reactions are common and have been linked to the liberation of excessively high concentrations of 6-mercaptopurine and corresponding toxic metabolites. An allelic variant of thiopurine methyltransferase with low activity is associated with elevated concentrations of 6-mercaptopurine. However, other genetic markers remain to be identified in order to fully account for adverse reactions and efficacy failure. In the present study, we studied the five known allelic variants of human glutathione transferase A2-2 (GST A2-2) (EC2.5.1.18), abundantly expressed in liver and efficiently catalyzing the bioactivation of azathioprine to release 6-mercaptopurine. All five variants exhibited high activity with azathioprine, but allelic variant E of GST A2-2 displayed a 3-4-fold elevated catalytic efficiency compared to the other variants. High GST activity can lead to overproduction of 6-mercaptopurine, and the nature of the multiple forms of GSTs in a patient will obviously affect the metabolism of azathioprine. In addition to GST A2-2, the polymorphic GST M1-1 is also highly active with azathioprine. Considering our findings, it appears that the genotypic and phenotypic variations in the GST complement may influence the presentation of adverse reactions in patients treated with azathioprine. Clinical trials will be required to clarify the impact of the GST expression in comparison with the established biomarker thiopurine methyltransferase as predictors of adverse reactions.

  • 5925.
    Zhang, Wei
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för biokemi och organisk kemi.
    Modén, Olof
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för biokemi och organisk kemi.
    Tars, Kaspars
    Biomedical Research and Study Center, LV-1067 Riga, Latvia.
    Mannervik, Bengt
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för biokemi och organisk kemi.
    Structure-based redesign of GST A2-2 for enhanced catalytic efficiency with azathioprine2012Inngår i: Chemistry and Biology, ISSN 1074-5521, E-ISSN 1879-1301, Vol. 19, nr 3, s. 414-421Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Glutathione transferase (GST) A2-2 is the most efficient human enzyme in the biotransformation of the prodrug azathioprine (Aza). The activation of Aza has therapeutic potential for possible use of GSTs in targeted enzyme-prodrug treatment of diseases. Based on the assumed catalytic mechanism and computational docking of Aza to the active site of the enzyme, active-site residues were selected for construction of focused mutant libraries, which were thereafter screened for Aza activity. Mutants with elevated Aza activity were identified, DNA sequenced, and the proteins purified. The two most active mutants showed up to 70-fold higher catalytic efficiency than the parental GST A2-2. The structure of the most active triple mutant (L107G/L108D/F222H) enzyme was determined by X-ray crystallography demonstrating significant changes in the topography of the active site facilitating productive binding of Aza as a substrate. 

  • 5926. Zhang, X F
    et al.
    Meining, Winfried
    Södertörns högskola, Avdelning Naturvetenskap.
    Cushman, M
    Haase, I
    Fischer, M
    Bacher, A
    Ladenstein, R
    A structure-based model of the reaction catalyzed by lumazine synthase from Aquifex aeolicus2003Inngår i: Journal of Molecular Biology, ISSN 0022-2836, E-ISSN 1089-8638, Vol. 328, nr 1, s. 167-182Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    6,7-Dimethyl-8-ribityllumazine is the biosynthetic precursor of riboflavin, which, as a coenzyme, plays a vital role in the electron transfer process for energy production in all cellular organisms. The enzymes involved in lumazine biosynthesis have been studied in considerable detail. However, the conclusive mechanism of the reaction catalyzed by lumazine synthase has remained unclear. Here, we report four crystal structures of the enzyme from the hyperthermophilic bacterium Aquifex aeolicus in complex with different inhibitor compounds. The structures were refined at resolutions of 1.72 Angstrom, 1.85 Angstrom, 2.05 Angstrom and 2.2 Angstrom, respectively. The inhibitors have been designed in order to mimic the substrate, the putative reaction intermediates and the final product. Structural comparisons of the native enzyme and the inhibitor complexes as well as the kinetic data of singlesite mutants of lumazine synthase from Bacillus subtilis showed that several highly conserved residues at the active site, namely Phe22, His88, Arg127, Lys135 and Glu138 are most likely involved in catalysis. A structural model of the catalytic process, which illustrates binding of substrates, enantiomer specificity, proton abstraction/donation, inorganic phosphate elimination, formation of the Schiff base and cyclization is proposed.

  • 5927. Zhang, X F
    et al.
    Meining, Winfried
    Södertörns högskola, Avdelning Naturvetenskap.
    Fischer, M
    Bacher, A
    Ladenstein, R
    X-ray structure analysis and crystallographic refinement of lumazine synthase from the hyperthermophile Aquifex aeolicus at 1.6 angstrom resolution: Determinants of thermostability revealed from structural comparisons2001Inngår i: Journal of Molecular Biology, ISSN 0022-2836, E-ISSN 1089-8638, Vol. 306, nr 5, s. 1099-1114Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    An open reading frame optimized for expression of 6,7-dimethyl-8-ribityllumazine synthase of the hyperthermophilic bacterium Aquifex aeolicus in Escherichia coli was synthesized and expressed in a recombinant E. coli strain to a level of around 15%. The recombinant protein was purified by heat-treatment and gel-filtration. The protein was crystallized in the cubic space group 123 with the cell dimensions a = b = c = 180.8 Angstrom, and diffraction data were collected to 1.6 Angstrom resolution. The structure was solved by molecular replacement using lumazine synthase from Bacillus subtilis as search model. The structure of the A. aeolicus enzyme was refined to a resolution of 1.6 Angstrom. The spherical protein consists of 60 identical subunits with strict icosahedral 532 symmetry. The subunit fold is closely related to that of the B. subtilis enzyme (rmsd 0.80 Angstrom). The extremely thermostable lumazine synthase from A. aeolicus has a melting temperature of 119.9 degreesC. Compared to other icosahedral and pentameric lumazine synthases, the A. aeolicus enzyme has the largest accessible surface presented by charged residues and the smallest surface presented by hydrophobic residues. It also has the largest number of ion-pairs per subunit. Two ion-pair networks involving two, respectively three, stacking arginine residues assume a distinct role in linking adjacent subunits. The findings indicate the influence of the optimization of hydrophobic and ionic contacts in gaining thermostability.

  • 5928.
    Zhang, Xuan
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för biokemi och biofysik.
    Oglecka, Kamila
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för biokemi och biofysik.
    Sandgren, Staffan
    Belting, Mattias
    Esbjorner, Elin K.
    Norden, Bengt
    Gräslund, Astrid
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för biokemi och biofysik.
    Dual functions of the human antimicrobial peptide LL-37-Target membrane perturbation and host cell cargo delivery2010Inngår i: Biochimica et Biophysica Acta - Biomembranes, ISSN 0005-2736, E-ISSN 1879-2642, Vol. 1798, nr 12, s. 2201-2208Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The mechanisms behind target vs. host cell recognition of the human antimicrobial peptide LL-37 remain ill-defined. Here, we have investigated the membrane disruption capacity of LL-37 using large unilamellar vesicles (LUVs) composed of varying mixtures of POPC, POPG and cholesterol to mimic target and host membranes respectively. We show that LL-37 is unable to induce leakage of entrapped calcein from zwitterionic POPC LUVs, whereas leakage from LUVs partially composed of POPG is fast and efficient. In accordance with typical antimicrobial peptide behavior, cholesterol diminished LL-37 induced leakage. By using linear dichroism and flow oriented LUVs, we found that LL-37 orients with the axis of its induced alpha-helix parallel to the membrane surface in POPC:POPG (7:3) LUVs. In the same system, we also observed a time-dependent increase of the parallel alpha-helix LD signal on timescales corresponding to the leakage kinetics. The increased LD may be connected to a peptide translocation step, giving rise to mass balance across the membrane. This could end the leakage process before it is complete, similar to what we have observed. Confocal microscopy studies of eukaryotic cells show that LL-37 is able to mediate the cell delivery of non-covalently linked fluorescent oligonucleotides, in agreement with earlier studies on delivery of plasmid DNA (Sandgren et al., J. Biol. Chem. 279 (2004) 17951). These observations highlight the potential dual functions of LL-37 as an antimicrobial agent against bacterial target cells and a cell-penetrating peptide that can deliver nucleic acids into the host cells.

  • 5929.
    Zhang, Yang
    et al.
    KTH Royal Instute of Technology, Sweden.
    Xie, Sheng
    KTH Royal Instute of Technology, Sweden.
    Yan, Mingdi
    KTH Royal Instute of Technology, Sweden;Univ Massachusetts Lowell, USA.
    Ramström, Olof
    Linnéuniversitetet, Fakulteten för Hälso- och livsvetenskap (FHL), Institutionen för kemi och biomedicin (KOB). KTH Royal Instute of Technology, Sweden;Univ Massachusetts Lowell, USA.
    Enzyme- and ruthenium-catalyzed dynamic kinetic resolution involving cascade alkoxycarbonylations for asymmetric synthesis of 5-Substituted N-Aryloxazolidinones2019Inngår i: Molecular Catalysis, ISSN 2468-8274, Vol. 470, s. 138-144Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Asymmetric synthesis of N-aryloxazolidinones via dynamic kinetic resolution was developed. A ruthenium-based catalyst was used in the racemization of β-anilino alcohols, while Candida antarctica lipase B (CAL-B) was applied for two selective alkoxycarbonylations operating in cascade. Various N-aryloxazolidinone derivatives were obtained in high yields and good enantiopurities. © 2019 Elsevier B.V.

  • 5930.
    Zhang, Yanxiao
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för naturvetenskaplig biokemi.
    Chromatographic studies of interactions between solutes, lipid bilayers and the glucose transporter Glut11997Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    It is advantageous to analyze solute interactions with biological membranes by chromatography on stationary phases that mimic the membrane structures. In the present work, liposomes, proteoliposomes, human red cells and red cell membrane vesicles were immobilized for analyses ofinteractions between solutes (peptides, drugs, inhibitors and glucose), lipid bilayers and theglucose transporter Glut1.

    For microscale analysis of solute-membrane interactions, liposomes were immobilized incontinuous beds for capillary chromatography and included in the running buffer as pseudostationary phase in capillary electrophoresis. These techniques were convenient and rapid. Inchromatographic drug partitioning studies, the logarithm of the specific capacity factors determined on liposomes in capillary continuous beds showed a linear correlation with the logarithmof apparent drug permeabilities through Caco-2 epithelial cell monolayers.

    Peptide and drug interactions with lipid bilayers were analyzed by chromatography on liposomes immobilized in gel beads. The retardations of peptides corresponding to segments ofGlut1 were related to the transfer free energy distribution within the peptides and to the hydrophobicities of the peptides. The effects of pH. temperature, ionic strength, flow rate and phospholipid composition on the retardation of drugs on liposomes or membrane vesicles were studied.

    For the first time, human red cells were immobilized in gel particles for chromatographicactivity analyses. D-Glucose showed a larger retardation than L-glucose upon transport retentionchromatography and Glut1 in the cells showed high affinities for D-glucose and forskolin, asdetermined by frontal affinity analyses.

    For exceptionally stable immobilization, biotin-avidin binding was introduced. Glut1 inproteoliposomes immobilized by this method showed solute affinities similar to those of sterically immobilized proteoliposomes.

  • 5931.
    Zhang, Yongfei
    et al.
    DUT, DUT KTH Joint Educ & Res Ctr Mol Devices, State Key Lab Fine Chem, Inst Artificial Photosynth, Dalian 116024, Peoples R China..
    Liang, Yongqi
    DUT, DUT KTH Joint Educ & Res Ctr Mol Devices, State Key Lab Fine Chem, Inst Artificial Photosynth, Dalian 116024, Peoples R China..
    Wang, Yajuan
    DUT, DUT KTH Joint Educ & Res Ctr Mol Devices, State Key Lab Fine Chem, Inst Artificial Photosynth, Dalian 116024, Peoples R China..
    Guo, Fengwan
    Peking Univ, Beijing Natl Lab Mol Sci, State Key Lab Struct Chem Unstable & Stable Speci, Coll Chem & Mol Engn, Beijing 100871, Peoples R China..
    Sun, Licheng
    KTH, Skolan för kemivetenskap (CHE), Centra, Molekylär elektronik, CMD. KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Kemi.
    Xu, Dongsheng
    Peking Univ, Beijing Natl Lab Mol Sci, State Key Lab Struct Chem Unstable & Stable Speci, Coll Chem & Mol Engn, Beijing 100871, Peoples R China..
    Planar FAPbBr(3) Solar Cells with Power Conversion Efficiency above 10%2018Inngår i: ACS ENERGY LETTERS, ISSN 2380-8195, Vol. 3, nr 8, s. 1808-1814Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Bromide-based hybrid perovskites are of particular interest not only due to the fact that they offer a way to go beyond the Shockley-Queisser limit via the tandem cell scheme but single junction devices of them can also achieve reasonably high efficiency with high stability for solar energy conversion. However, the highest power conversion efficiency achieved up to now for FAPbBr(3) single-junction solar cells is only 8.2%, which is far below the efficiency of-17% predicted from detailed balance analysis. Here, a two-step method (the intermolecule exchange pathway) was systematically optimized for the fabrication of high quality FAPbBr(3) films. A molecule of urea, structurally similar to formamidinium, is introduced as an additive to tune the intermolecular ion exchange procedure. SnO2 is introduced as an electron-selective contact to the planar structured FAPbBr(3) solar cells. As a result, a power conversion efficiency of 10.61% and a V-oc of 1.56 V are achieved with planar structured solar cells, both of which represent the highest value ever reported for FAPbBr(3) solar cells.

  • 5932.
    Zhang, Yu
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Polymerkemi. Uppsala universitet, Science for Life Laboratory, SciLifeLab.
    Sun, Yi
    Yang, Xia
    Hilborn, Jöns
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Polymerkemi. Uppsala universitet, Science for Life Laboratory, SciLifeLab.
    Heerschap, Arend
    Ossipov, Dmitri A.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Polymerkemi. Uppsala universitet, Science for Life Laboratory, SciLifeLab.
    Injectable In Situ Forming Hybrid Iron Oxide-Hyaluronic Acid Hydrogel for Magnetic Resonance Imaging and Drug Delivery2014Inngår i: Macromolecular Bioscience, ISSN 1616-5187, E-ISSN 1616-5195, Vol. 14, nr 9, s. 1249-1259Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The development of multimodal in situ cross-linkable hyaluronic acid nanogels hybridized with iron oxide nanoparticles is reported. Utilizing a chemoselective hydrazone coupling reaction, the nanogels are converted to a macroscopic hybrid hydrogel without any additional reagent. Hydrophobic cargos remain encapsulated in the hydrophobic domains of the hybrid hydrogel without leakage. However, hydrogel degradation with hyaluronidase liberates iron oxide nanoparticles. This allows the utilization of imaging agents as tracers of the hydrogel degradation. UV-vis spectrometry and MRI studies reveal that the degradability of the hydrogels correlates with their structure. The hydrogels presented here are very promising theranostic tools for hyaluronidase-mediated delivery of hydrophobic drugs, as well as imaging of hydrogel degradation and tracking of degradation products in vivo.

  • 5933.
    Zhang, Yujia
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Träkemi och massateknologi.
    Li, Jiebing
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Träkemi och massateknologi. KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center.
    Lindström, Mikael E.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Träkemi och massateknologi. KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center.
    Mischnick, Petra
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi. Technische Universität Braunschweig, Germany .
    Relative reactivities in the O-methylation of glucomannans: the influence of stereochemistry at C-2 and the solvent effect2015Inngår i: Carbohydrate Research, ISSN 0008-6215, E-ISSN 1873-426X, Vol. 402, s. 172-179Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The main hemicellulose in softwood, glucomannan (GM), structurally resembles cellulose but has quite different physical and chemical properties. In addition to branching and original acetylation, the only other difference between these two beta-1,4-linked glycans is the configuration at C-2 in approximately 80% of the sugar residues. In contrast to glucose, the 2-OH in mannose has an axial orientation. The influence of this stereochemistry on the relative reactivities of glucosyl compared to mannosyl units in methylation reactions are studied in this work. Glucomannan isolated from spruce (SGM) and commercially available konjac glucomannan (KGM) was methylated in DMSO/Li-dimsyl/MeI and water/NaOH/MeI system, respectively. In the early stage of the reaction, the glucose part of the SGM achieved slightly higher DS values than the mannose residues, but the overall relative rate constants were close to 1:1. The order of reactivities in glucose was k(2) > k(3) > k(6) and k(3) > k(2) > k(6) for mannose (in DMSO/Li-dimsyl/MeI). The rate constants did not remain constant, but k(3) decreased when k(2) increased for both epimeric sugars. In water/NaOH/MeI, the methylation of the primary 6-OH was much more pronounced with an order of reactivity of O-6 > O-2 > O-3 for mannose and O-2 > O-6 > O-3 for glucose. The results are discussed with respect to the OH-acidity and the stereoelectronic, sterical, and solvent effects.

  • 5934.
    Zhang, Zhe
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för biokemi och biofysik.
    Enhancing membrane and secretory protein production yields in Escherichia coli2020Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Proteins fulfill essential functions in living cells. To produce sufficient amounts of a protein is essential to study the structure and function of a protein, or to use it for medical purposes. Escherichia coli is a Gram-negative bacterium that is widely used for recombinant protein production. The aim of my PhD studies was to enhance membrane and secretory protein production yields using E. coli. The T7-based protein production system BL21(DE3)/pET was mainly used in my studies. BL21(DE3) contains a strong IPTG-inducible lacUV5 promoter governing the expression of the t7rnap gene encoding the T7RNAP on its chromosome. The target gene is under control of the T7 promoter on the pET plasmid. T7RNAP specifically recognizes the T7 promoter and transcribes the target gene more efficiently than the bacterial RNAP. Unfortunately, the biogenesis machinery for membrane and secretory proteins is usually saturated by the high protein production intensity when the BL21(DE3)/pET system is induced with IPTG, thereby negatively affecting protein production yields. In the first study, we found that when using the BL21(DE3)/pET system omitting the inducer IPTG improved membrane and secretory protein production yields. In previous studies, Lemo21(DE3) was developed to facilitate the production of membrane and secretory proteins. Lemo21(DE3) contains the pLemo plasmid in which the gene encoding the inhibitor of T7RNAP, T7 lysozyme, is under the control of the rhaBAD promoter. The activity of T7RNAP is regulated by synthesizing different levels of T7 lysozyme by adding different amounts of rhamnose. Thus, the production intensity can be modulated such that the biogenesis machinery of membrane and secretory proteins is not saturated upon IPTG induction. In the second study, we combined the key elements from both the pLemo and pET vectors to create the pReX (Regulated eXpression) plasmid to facilitate the use of helper plasmids encoding e.g., chaperones when it is necessary. In the third study, we used the rhaBAD promoter to direct the production of membrane and secretory proteins in a rhamnose metabolism and active uptake deficient strain. The protein production rate can be truly tuned in this setup. Therefore, the production of membrane and secretory proteins can be enhanced by using the right amount of rhamnose in the culture medium. BL21(DE3) contains the λDE3 prophage that carries the t7rnap gene under the control of the lacUV5 promoter. The λDE3 prophage is thought to be stably inserted into the chromosome, but the lytic cycle of the prophage can still be induced by the SOS response inducing antibiotic mitomycin C in the mitomycin C-based bacteriophage test. In the fourth study, we engineered BL21T7 by deleting in BL21(DE3) lysis related genes from the prophage. BL21T7 has similar recombinant protein production characteristics as its ancestor BL21(DE3).

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  • 5935.
    Zhang, Zhe
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för biokemi och biofysik.
    Ampah-Korsah, Henry
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för biokemi och biofysik.
    Karyolaimos, Alexandros
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för biokemi och biofysik.
    de Gier, Jan-Willem
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för biokemi och biofysik.
    Construction and characterization of the bacteriophage testable BL21(DE3)-derivative BL21T7Manuskript (preprint) (Annet vitenskapelig)
  • 5936.
    Zhang, Zhen
    et al.
    Umeå universitet, Medicinska fakulteten, Institutionen för molekylärbiologi (Medicinska fakulteten). Umeå universitet, Medicinska fakulteten, Molekylär Infektionsmedicin, Sverige (MIMS).
    Aung, Kyaw Min
    Umeå universitet, Medicinska fakulteten, Molekylär Infektionsmedicin, Sverige (MIMS). Umeå universitet, Medicinska fakulteten, Institutionen för molekylärbiologi (Medicinska fakulteten).
    Uhlin, Bernt Eric
    Umeå universitet, Medicinska fakulteten, Molekylär Infektionsmedicin, Sverige (MIMS). Umeå universitet, Medicinska fakulteten, Institutionen för molekylärbiologi (Medicinska fakulteten).
    Wai, Sun Nyunt
    Umeå universitet, Medicinska fakulteten, Institutionen för molekylärbiologi (Medicinska fakulteten). Umeå universitet, Medicinska fakulteten, Molekylär Infektionsmedicin, Sverige (MIMS).
    Reversible senescence of human colon cancer cells after blockage of mitosis/cytokinesis caused by the CNF1 cyclomodulin from Escherichia coli2018Inngår i: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 8, artikkel-id 17780Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Cytotoxic necrotizing factor 1 (CNF1), a protein toxin produced by extraintestinal pathogenic Escherichia coli, activates the Rho-family small GTPases in eukaryotic cell, thereby perturbing multiple cellular functions. Increasing epidemiological evidence suggests a link between CNF1 and human inflammatory bowel disease and colorectal cancer. At the cellular level, CNF1 has been hypothesized to reprogram cell fate towards survival due to the role in perturbing cell cycle and apoptosis. However, it remains undetermined how cells survive from CNF1 intoxication. In this work, we show that CNF1 treatment blocks mitosis/cytokinesis, elicits endoreplication and polyploidisation in cultured human colon cancer cells, and drives them into reversible senescence, which provides a survival route for cells via depolyploidisation. Senescence in CNF1-treated cells is demonstrated with upregulation of several senescence markers including senescence-associated β-galactosidase activity, p53, p21 and p16, and concomitant inhibition of the retinoblastoma protein phosphorylation. Importantly, progeny derived from CNF1 treatment exhibit genomic instability exemplified by increased aneuploidy and become more resistant to CNF1, but not to 5-fluorouracil and oxaliplatin, the two agents commonly used in chemotherapeutic treatment for colorectal cancer. These observations display survival features of the cell after CNF1 treatment that may have implications for the potential role of CNF1 in carcinogenesis.

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  • 5937. Zhao, Chengsong
    et al.
    Lasses, Theres
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Umeå Plant Science Centre (UPSC). Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysiologisk botanik.
    Bako, Laszlo
    Kong, Danyu
    Zhao, Bingyu
    Chanda, Bidisha
    Bombarely, Aureliano
    Cruz-Ramírez, Alfredo
    Scheres, Ben
    Brunner, Amy M.
    Beers, Eric P.
    XYLEM NAC DOMAIN1, an angiosperm NAC transcription factor, inhibits xylem differentiation through conserved motifs that interact with RETINOBLASTOMA-RELATED2017Inngår i: New Phytologist, ISSN 0028-646X, E-ISSN 1469-8137, Vol. 216, nr 1, s. 76-89Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The Arabidopsis thaliana gene XYLEM NAC DOMAIN1 (XND1) is upregulated in xylem tracheary elements. Yet overexpression of XND1 blocks differentiation of tracheary elements. The molecular mechanism of XND1 action was investigated. Phylogenetic and motif analyses indicated that XND1 and its homologs are present only in angiosperms and possess a highly conserved C-terminal region containing linear motifs (CKII-acidic, LXCXE, E2F(TD)-like and LXCXE-mimic) predicted to interact with the cell cycle and differentiation regulator RETINOBLASTOMA-RELATED (RBR). Protein-protein interaction and functional analyses of XND1 deletion mutants were used to test the importance of RBR-interaction motifs. Deletion of either the LXCXE or the LXCXE-mimic motif reduced both the XND1-RBR interaction and XND1 efficacy as a repressor of differentiation, with loss of the LXCXE motif having the strongest negative impacts. The function of the XND1 C-terminal domain could be partially replaced by RBR fused to the N-terminal domain of XND1. XND1 also transactivated gene expression in yeast and plants. The properties of XND1, a transactivator that depends on multiple linear RBR-interaction motifs to inhibit differentiation, have not previously been described for a plant protein. XND1 harbors an apparently angiosperm-specific combination of interaction motifs potentially linking the general differentiation regulator RBR with a xylem-specific pathway for inhibition of differentiation.

  • 5938.
    Zhao, Guang-Hui
    et al.
    Key Laboratory of Trace Elements and Endemic Diseases of National Health and Family Planning Commission, Collaborative Innovation Center of Endemic Diseases and Health Promotion in Silk Road Region, School of Public Health, Health Science Center, Xi'an Jiaotong University, Xi'an, People's Republic of China.
    Yang, Lei
    Key Laboratory of Trace Elements and Endemic Diseases of National Health and Family Planning Commission, Collaborative Innovation Center of Endemic Diseases and Health Promotion in Silk Road Region, School of Public Health, Health Science Center, Xi'an Jiaotong University, Xi'an, People's Republic of China; School of Nursing, Health Science Center, Xi'an Jiaotong University, Xi'an, People's Republic of China; School of Nursing, Health Science Center, Xi'an Jiaotong University, Xi'an, Shaanxi, People's Republic of China.
    Lammi, Mikko
    Umeå universitet, Medicinska fakulteten, Institutionen för integrativ medicinsk biologi (IMB). Key Laboratory of Trace Elements and Endemic Diseases of National Health and Family Planning Commission, Collaborative Innovation Center of Endemic Diseases and Health Promotion in Silk Road Region, School of Public Health, Health Science Center, Xi'an Jiaotong University, Xi'an, People's Republic of China.
    Guo, Xiong
    Key Laboratory of Trace Elements and Endemic Diseases of National Health and Family Planning Commission, Collaborative Innovation Center of Endemic Diseases and Health Promotion in Silk Road Region, School of Public Health, Health Science Center, Xi'an Jiaotong University, Xi'an, People's Republic of China.
    A preliminary analysis of microRNA profiles in the subchondral bone between Kashin-Beck disease and primary knee osteoarthritis2019Inngår i: Clinical Rheumatology, ISSN 0770-3198, E-ISSN 1434-9949, Vol. 38, nr 9, s. 2637-2645, artikkel-id 31062252Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    INTRODUCTION: Kashin-Beck disease (KBD) is a chronic osteochondral disorder primarily associated with cartilage degeneration. The bone texture structure in KBD was also changed but it was not identical to primary knee osteoarthritis (OA). This study investigates the differences in microRNA (miRNA) profiles of subchondral bone collected from patients suffering from KBD in comparison with those with primary knee osteoarthritis (OA).

    METHODS: Subchondral bone tissues were taken from four patients with KBD and four patients with primary knee OA undergoing total knee replacement. The miRNA array profiling was performed using an Affymetrix miRNA 4.0 Array, and then the target gene predictions and function annotations of the predicted targets were performed.

    RESULTS: Our results showed that 124 miRNAs had lower expression levels in the subchondral bone sampled from KBD patients in comparison with OA patients. Gene ontology (GO) and KEGG pathway analyses of the predicted targets demonstrated numerous significantly enriched GO terms and signal pathways essential for bone development and integrity, such as metabolic processes, PI3K-Akt, and MAPK signaling pathways.

    CONCLUSIONS: Our study confirms that a large set of miRNAs are differentially expressed in the subchondral bone of patients with KBD and OA and contributes new insights into potential pathological changes in the subchondral bone of KBD patients.

  • 5939.
    Zhao, Linshu
    Uppsala universitet, Medicinska vetenskapsområdet, Medicinska fakulteten, Institutionen för medicinska vetenskaper, Klinisk kemi.
    CarcinoEmbryonic Antigen-related Cell Adhesion Molecule 8 (CEACAM8): Purification, Characterization, Cellular and Clinical Studies2004Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    A 95-kDa protein was purified from normal human granulocytes. The protein reacted with a monoclonal antibody against CEACAM8. MALDI-Tof and MS/MS analyses revealed the protein to be a CGM6 gene product. Thus, the protein was proved to be identical to CEACAM8.

    An ELISA for CEACAM8 was developed with detection range of 1-64μg/L. Data are presented on the levels of CEACAM8 in the blood of healthy individuals and patients undergoing surgery, as well as in patients with acute infection. The highly elevated levels of CEACAM8 in the blood of these patients were significantly correlated with the surface expression of CEACAM8 on neutrophils and the number of circulating neutrophils, which suggests that CEACAM8 could serve as a biological marker for granulocyte activitiy in vivo.

    The cellular content of CEACAM8 in neutrophils was estimated to be 82.4 ± 8.9 ng/106 cells. Subcellular localisation and mobilisation studies showed that the majority of CEACAM8 is present in the secondary granules of human neutrophils, with a small amount on the plasma membranes. Upon stimulation, CEACAM8 translocated to the plasma membranes from the secondary granules and was also released extracellularly (5.5 ± 0.7% of the total content of CEACAM8).

    In eosinophils, the cellular content of CEACAM8 was estimated to be 73.8 ± 6.0 ng/106 cells. In these cells, CEACAM8 is mainly stored in secretory vesicles. Upon activation, eosinophils released 5.1 ± 1.1% of the total content of CEACAM8.

    Administration of granulocyte colony-stimulating factor (G-CSF) to healthy individuals resulted in an increased content of CEACAM8 in neutrophils on day 1, and decreased on day 4. However, the content of CEACAM8 in light membrane fractions was increased on day 4. The translocation of CEACAM8 observed in vivo after G-CSF administration is probably not directly related to this cytokine but to other cytokines such as TNF-a.

    Fulltekst (pdf)
    FULLTEXT01
  • 5940.
    Zhao, Tao
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Organisk kemi.
    Krokene, Paal
    Björklund, Niklas
    Långström, Bo
    Solheim, Halvor
    Christiansen, Erik
    Borg-Karlson, Anna-Karin
    KTH, Skolan för kemivetenskap (CHE), Kemi, Organisk kemi.
    The influence of Ceratocystis polonica inoculation and methyl jasmonate application on terpene chemistry of Norway spruce, Picea abies2010Inngår i: Phytochemistry, ISSN 0031-9422, E-ISSN 1873-3700, Vol. 71, nr 11-12, s. 1332-1341Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Constitutive and inducible terpene production is involved in conifer resistance against bark beetles and their associated fungi. In this study 72 Norway spruce (Picea abies) were randomly assigned to methyl jasmonate (MJ) application, inoculation with the bluestain fungus Ceratocystis polonica, or no-treatment control. We investigated terpene levels in the stem bark of the trees before treatment, 30 days and one year after treatment using GC-MS and two-dimensional GC (2D-GC) with a chiral column, and monitored landing and attack rates of the spruce bark beetle, Ips typographus, on the trees by sticky traps and visual inspection. Thirty days after fungal inoculation the absolute amount and relative proportion of (+)-3-carene, sabinene, and terpinolene increased and (+)-alpha-pinene decreased. Spraying the stems with MJ tended to generally increase the concentration of most major terpenes with minor alteration to their relative proportions, but significant increases were only observed for (-)-beta-pinene and (-)-limonene. Fungal inoculation significantly increased the enantiomeric ratio of (-)-alpha-pinene and (-)-limonene 1 month after treatment, whereas MJ only increased that of (-)-limonene. One year after treatment, both MJ and fungal inoculation increased the concentration of most terpenes relative to undisturbed control trees, with significant changes in (-)-beta-pinene, (-)-beta-phellandrene and some other compounds. Terpene levels did not change in untreated stem sections after treatment, and chemical induction by MJ and C polonica thus seemed to be restricted to the treated stem section. The enantiomeric ratio of (-)-alpha-pinene was significantly higher and the relative proportions of ( -)-limonene were significantly lower in trees that were attractive to bark beetles compared to unattractive trees. One month after fungal inoculation, the total amount of diterpenes was significantly higher in putative resistant trees with shorter lesion lengths than in putative susceptible trees with longer lesions. Thus, terpene composition in the stem bark may be related to resistance of Norway spruce against I. typographus and C. polonica.

  • 5941.
    Zhao, Weizhou
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för cell- och molekylärbiologi, Molekylär evolution.
    Andersson, Siv G. E.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för cell- och molekylärbiologi, Molekylär evolution.
    Single cell genomics of deep ocean bacteria2014Inngår i: Trends in Microbiology, ISSN 0966-842X, E-ISSN 1878-4380, Vol. 22, nr 5, s. 233-234Artikkel i tidsskrift (Annet vitenskapelig)
    Abstract [en]

    SAR11 is one of the most abundant bacterioplanktons in the upper surface waters of the oceans. In a recent issue of The ISME Journal, Thrash and colleagues present the genomes of four single SAR11 cells isolated from the deep oceans that are enriched in genes for membrane biosynthetic functions.

  • 5942.
    Zhao, Yani
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för cell- och molekylärbiologi, Mikrobiologi.
    Holmgren, Benjamin T.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för cell- och molekylärbiologi, Mikrobiologi.
    Hinas, Andrea
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för cell- och molekylärbiologi, Mikrobiologi.
    The conserved SNARE SEC-22 localizes to late endosomes and negatively regulates RNA interference in Caenorhabditis elegans2017Inngår i: RNA: A publication of the RNA Society, ISSN 1355-8382, E-ISSN 1469-9001, Vol. 23, nr 3, s. 297-307Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Small RNA pathways, including RNA interference (RNAi), play crucial roles in regulation of gene expression. Initially considered to be cytoplasmic, these processes have later been demonstrated to associate with membranes. For example, maturation of late endosomes/multivesicular bodies (MVBs) is required for efficient RNAi, whereas fusion of MVBs to lysosomes appears to reduce silencing efficiency. SNAREs (soluble N-ethylmaleimide-sensitive factor attachment protein receptors) mediate membrane fusion and are thus at the core of membrane trafficking. In spite of this, no SNARE has previously been reported to affect RNAi. Here, we demonstrate that in Caenorhabditis elegans, loss of the conserved SNARE SEC-22 results in enhanced RNAi upon ingestion of double-stranded RNA. Furthermore, SEC-22 overexpression inhibits RNAi in wild-type animals. We find that overexpression of SEC-22 in the target tissue (body wall muscle) strongly suppresses the sec-22(-) enhanced RNAi phenotype, supporting a primary role for SEC-22 in import of RNAi silencing signals or cell autonomous RNAi. A functional mCherry:: SEC-22 protein localizes primarily to late endosomes/MVBs and these compartments are enlarged in animals lacking sec-22. SEC-22 interacts with late endosome-associated RNA transport protein SID-5 in a yeast two-hybrid assay and functions in a sid-5-dependent manner. Taken together, our data indicate that SEC-22 reduces RNAi efficiency by affecting late endosome/MVB function, for example, by promoting fusion between late endosomes/MVBs and lysosomes. To our knowledge, this is the first report of a SNARE with a function in small RNA-mediated gene silencing.

    Fulltekst (pdf)
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  • 5943.
    Zhao, Zeng-Ren
    et al.
    Department of General Surgery, The First Hospital of Hebei Medical University, Shijiazhuang, P.R. China.
    Zhang, Zhi-Yong
    Department of Oncology, Institute of Biomedicine and Surgery, Linköping University, Linköping, Sweden / Department of Pathology, Tangshan Gongren Hospital, Tangshan, P.R. China.
    Zhang, Hong
    Department of Dermatology, Institute of Biomedicine and Surgery, Linköping University, Linköping, Sweden.
    Jiang, Li
    Department of Pathology, Tangshan Gongren Hospital, Tangshan, P.R. China.
    Wang, Ming-Wei
    Laboratory Centre, The First Hospital of Hebei Medical University, Shijiazhuang, P.R. China.
    Sun, Xiao-Feng
    Department of Oncology, Institute of Biomedicine and Surgery, Linköping University, Linköping, Sweden.
    Overexpression of Id-1 protein is a marker in colorectal cancer progression2008Inngår i: Oncology Reports, ISSN 1021-335X, E-ISSN 1791-2431, Vol. 19, nr 2, s. 419-424Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Abstract: The inhibitor of differentiation/DNA binding 1 (Id-1), a negative regulator of basic helix-loop-helix transcription factors, plays an important role in the regulation of cell proliferation and differentiation. We examined the Id-1 expression by immunohistochemistry in 9 adenomas, 79 primary colorectal adenocarcinomas matched with 40 adjacent normal mucosa specimens and its relationship with clinicopathological factors. The Id-1 expression was increased in the carcinoma compared to the adjacent normal mucosa either in the unmatched and matched samples or to the adenoma. There was no significant difference in the Id-1 expression between normal mucosa and adenoma. The Id-1 expression of carcinoma was increased from Dukes' stages A to B, to C and to D. The cases with lymph node metastasis had a higher rate of a stronger Id-1 expression than those without lymph node metastasis. In conclusion, Id-1 overexpression plays an important role in colorectal cancer progression.

  • 5944.
    Zhenyu Gu, Weidenhaupt, M, Ivanova, I, Pavlov, M, Xu, B, Zhi-Guo, S and Jansson, J-C
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Teknisk-naturvetenskapliga fakulteten, Biologiska sektionen, Institutionen för cell- och molekylärbiologi. MOLEKYLÄRBIOLOGI.
    Chromoatographic Methods for the Insolation of, and Refolding of Proteins forms, Escherichia coli Inclusion Bodies2002Inngår i: journal, Vol. 25, s. 174-179Artikkel i tidsskrift (Fagfellevurdert)
  • 5945.
    Zhongwei, Yuan
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för cell- och molekylärbiologi.
    Akula, Srinivas
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för cell- och molekylärbiologi, Mikrobiologi.
    Fu, Zhirong
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för cell- och molekylärbiologi, Mikrobiologi.
    de Garavilla, Lawrence
    GDL Pharmaceut Consulting & Contracting, Downingtown, PA 19335 USA.
    Kervinen, Jukka
    Tosoh Biosci LLC, 3604 Horizon Dr, King Of Prussia, PA 19406 USA.
    Thorpe, Michael
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för cell- och molekylärbiologi, Mikrobiologi.
    Hellman, Lars
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för cell- och molekylärbiologi, Mikrobiologi.
    Extended Cleavage Specificities of Rabbit and Guinea Pig Mast Cell Chymases: Two Highly Specific Leu-Ases2019Inngår i: International Journal of Molecular Sciences, ISSN 1422-0067, E-ISSN 1422-0067, Vol. 20, nr 24, artikkel-id 6340Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Serine proteases constitute the major protein content of mast cell (MC) secretory granules. These proteases can generally be subdivided into chymases and tryptases based on their primary cleavage specificity. Here, we presented the extended cleavage specificities of a rabbit beta-chymase and a guinea pig alpha-chymase. Analyses by phage display screening and a panel of recombinant substrates showed a marked similarity in catalytic activity between the enzymes, both being strict Leu-ases (cleaving on the carboxyl side of Leu). Amino acid sequence alignment of a panel of mammalian chymotryptic MC proteases and 3D structural modeling identified an unusual residue in the rabbit enzyme at position 216 (Thr instead of more common Gly), which is most likely critical for the Leu-ase specificity. Almost all mammals studied, except rabbit and guinea pig, express classical chymotryptic enzymes with similarly extended specificities, indicating an important role of chymase in MC biology. The rabbit and guinea pig are the only two mammalian species currently known to lack a classical MC chymase. Key questions are now how this major difference affects their MC function, and if genes of other loci can rescue the loss of a chymotryptic activity in MCs of these two species.

    Fulltekst (pdf)
    FULLTEXT01
  • 5946.
    Zhou, Chuanzheng
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för bioorganisk kemi.
    Honcharenko, Dmytro
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för bioorganisk kemi.
    Chattopadhyaya, Jyoti
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för bioorganisk kemi.
    2-(4-Tolylsulfonyl)ethoxymethyl (TEM)-a new 2'-OH protecting group for solid-supported RNA synthesis2007Inngår i: Organic and biomolecular chemistry, ISSN 1477-0520, E-ISSN 1477-0539, Vol. 5, nr 2, s. 333-343Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The 2-(4-tolylsulfonyl) ethoxymethyl (TEM) as a new 2'-OH protecting group is reported for solid-supported RNA synthesis using phosphoramidite chemistry. The usefulness of the 2'-O-TEM group is exemplified by the synthesis of 12 different oligo-RNAs of various sizes ( 14 - 38 nucleotides long). The stepwise coupling yield varied from 97 - 99% with an optimized coupling time of 120 s. The synthesis of all four pure phosphoramidite building blocks is also described. Two new reliable parameters, delta(C2') - delta(C3') and delta(H2') - delta(H3'), have been suggested for the characterization of isomeric 2'-O-TEM and 3'-O-TEM as well as other isomeric mono 2'/3'-protected ribonucleoside derivatives. The most striking feature of this strategy is that the crude RNA prepared using our 2'-O-TEM strategy is sufficiently pure (> 90%) for molecular biology research without any additional purification step, thereby making oligo-RNAs easily available at a relatively low cost, saving both time and lab resources.

  • 5947.
    Zhou, Chuanzheng
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för bioorganisk kemi.
    Pathmasiri, Wimal
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för bioorganisk kemi.
    Honcharenko, Dmytro
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för bioorganisk kemi.
    Chatterjee, Subhrangsu
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för bioorganisk kemi.
    Barman, Jharna
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för bioorganisk kemi.
    Chattopadhyaya, Jyoti
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för bioorganisk kemi.
    High-quality oligo-RNA synthesis using the new 2′-O-TEM protecting group by selectively quenching the addition of p-tolyl vinyl sulphone to exocyclic amino functions2007Inngår i: Canadian journal of chemistry (Print), ISSN 0008-4042, E-ISSN 1480-3291, Vol. 85, nr 4, s. 293-301Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    During the F--promoted deprotection of the oligo-RNA, synthesized using our 2′-O-(4-tolylsulfonyl)ethoxymethyl (2′-O-TEM) group [Org. Biomol. Chem. 5, 333 (2007)], p-tolyl vinyl sulphone (TVS) is formed as a by-product. The TVS formed has been shown to react with the exocyclic amino functions of adenosine (A), guanosine (G), and cytidine (C) of the fully deprotected oligo-RNA to give undesirable adducts, which are then purified by HPLC and unambiguously characterized by 1H, 13C Heteronuclear Multiple Bond Correlation (HMBC) NMR and mass spectroscopic analysis. The relative nucleophilic reactivities of the nucleobases toward TVS have been found to be the following: N6-A > N4-C > N2-G > > N3-U. This reactivity of TVS toward RNA nucleobases to give various Michael adducts could, however, be suppressed by using various amines as scavengers. Among all these amines, morpholine and piperidine are the most efficient scavenger for TVS, which gave highly pure oligo-RNA even in the crude form and can be used directly in RNA chemical biology studies.

  • 5948.
    Zhou, Juan
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemi.
    Butchosa, Nuria
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Jayawardena, H. Surangi N.
    Zhou, Qi
    KTH, Skolan för bioteknologi (BIO), Glykovetenskap. KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center.
    Yan, Mingdi
    KTH, Skolan för kemivetenskap (CHE), Kemi.
    Ramström, Olof
    KTH, Skolan för kemivetenskap (CHE), Kemi, Organisk kemi.
    Glycan-Functionalized Fluorescent Chitin Nanocrystals for Biorecognition Applications2014Inngår i: Bioconjugate chemistry, ISSN 1043-1802, E-ISSN 1520-4812, Vol. 25, nr 4, s. 640-643Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A new platform based on chitin nanocrystals has been developed for biorecognition applications. TEMPO-oxidized chitin nanocrystals (TCNs) were labeled with a fluorescent imidazoisoquinolinone dye, and simultaneously conjugated with carbohydrate ligands, resulting in dually functionalized TCNs. The biorecognition properties of the nanocrystals were probed with lectins and bacteria, resulting in selective interactions with their corresponding cognate carbohydrate-binding proteins, as visualized by optical, fluorescence, STEM, and TEM imaging. This represents a new approach to multifunctional nanomaterials based on naturally occurring polymers, holding high potential for biomedical applications.

  • 5949. Zhou, Ping
    et al.
    Zhai, Shanli
    Zhou, Xiang
    Lin, Ping
    Jiang, Tengfei
    Hu, Xueying
    Jiang, Yunbo
    Wu, Bin
    Zhang, Qingde
    Xu, Xuewen
    Li, Jin-Ping
    Uppsala universitet, Medicinska och farmaceutiska vetenskapsområdet, Medicinska fakulteten, Institutionen för medicinsk biokemi och mikrobiologi.
    Liu, Bang
    Molecular characterization of transcriptome-wide interactions between highly pathogenic porcine reproductive and respiratory syndrome virus and porcine alveolar macrophages in vivo2011Inngår i: International Journal of Biological Sciences, ISSN 1449-2288, E-ISSN 1449-2288, Vol. 7, nr 7, s. 947-959Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Porcine reproductive and respiratory syndrome virus (PRRSV) infects mainly the porcine alveolar macrophages (PAMs) and causes porcine reproductive and respiratory syndrome (PRRS). Previous studies have analyzed the global gene expression profiles of lung tissue in vivo and PAMs in vitro following infection with PRRSV, however, transcriptome-wide understanding of the interaction between highly pathogenic PRRSV (HP-PRRSV) and PAMs in vivo has not yet been established. In this study, we employed Affymetrix microarrays to investigate the gene expression patterns of PAMs isolated from Tongcheng piglets (a Chinese indigenous breed) after infection with HP-PRRSV. During the infection, Tongcheng piglets exhibited typical clinical signs, e.g. fever, asthma, coughing, anorexia, lethargy and convulsion, but displayed mild regional lung damage at 5 and 7 dpi. Microarray analysis revealed that HP-PRRSV infection has affected PAMs in expression of the important genes involved in cytoskeleton and exocytosis organization, protein degradation and folding, intracellular calcium and zinc homeostasis. Several potential antiviral strategies might be employed in PAMs, including upregulating IFN-induced genes and increasing intracellular zinc ion concentration. And inhibition of the complement system likely attenuated the lung damage during HP-PRRSV infection. Transcriptomic analysis of PAMs in vivo could lead to a better understanding of the HP-PRRSV-host interaction, and to the identification of novel antiviral therapies and genetic components of swine tolerance/susceptibility to HP-PRRS.

  • 5950.
    Zhou, Qi
    et al.
    KTH, Skolan för bioteknologi (BIO), Glykovetenskap.
    Baumann, Martin J.
    KTH, Skolan för bioteknologi (BIO), Glykovetenskap.
    Piispanen, Peter S.
    KTH, Skolan för bioteknologi (BIO), Glykovetenskap.
    Teeri, Tuula T.
    KTH, Skolan för bioteknologi (BIO), Glykovetenskap.
    Brumer, Harry
    KTH, Skolan för bioteknologi (BIO), Glykovetenskap.
    Xyloglucan and xyloglucan endo-transglycosylases (XET): Tools for ex vivo cellulose surface modification2006Inngår i: Biocatalysis and Biotransformation, ISSN 1024-2422, E-ISSN 1029-2446, Vol. 24, nr 1-2, s. 107-120Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Wood fibres constitute a renewable raw material for the production of novel biomaterials. The development of efficient methods for cellulose surface modification is essential for expanding the properties of wood fibres for increased reactivity and compatibility with other materials. By combining the high affinity between xyloglucan and cellulose, the unique mechanistic property of xyloglucan endo-transglycosylases (XET, EC 2.4.1.207) to catalyze polysaccharide-oligosaccharide coupling reactions, and traditional carbohydrate synthesis, a new system for the attachment of a wide variety of functional groups to wood pulps has been generated. An overview of recent developments is presented in the context of the structure, physical properties, and historical applications of xyloglucan.

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