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  • 1.
    Bergstrand, Jan
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Experimental Biomolecular Physics.
    Rönnlund, Daniel
    KTH, School of Engineering Sciences (SCI), Applied Physics, Experimental Biomolecular Physics.
    Widengren, Jerker
    KTH, School of Engineering Sciences (SCI), Applied Physics, Experimental Biomolecular Physics.
    Wennmalm, Stefan
    KTH, School of Engineering Sciences (SCI), Applied Physics, Experimental Biomolecular Physics. KTH, Centres, Science for Life Laboratory, SciLifeLab.
    Scanning inverse fluorescence correlation spectroscopy2014In: Optics Express, ISSN 1094-4087, E-ISSN 1094-4087, Vol. 22, no 11, p. 13073-13090Article in journal (Refereed)
    Abstract [en]

    Scanning Inverse Fluorescence Correlation Spectroscopy (siFCS) is introduced to determine the absolute size of nanodomains on surfaces. We describe here equations for obtaining the domain size from cross-and auto-correlation functions, measurement simulations which enabled testing of these equations, and measurements on model surfaces mimicking membranes containing nanodomains. Using a confocal microscope of 270 nm resolution the size of 250 nm domains were estimated by siFCS to 257 +/- 12 nm diameter, and 40 nm domains were estimated to 65 +/- 26 nm diameter. Applications of siFCS for sizing of nanodomains and protein clusters in cell membranes are discussed.

  • 2. Giraldo, Ana M. Villamil
    et al.
    Fyrner, Timmy
    Wennmalm, Stefan
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Parikh, Atul N.
    Ollinger, Karin
    Ederth, Thomas
    Spontaneous Vesiculation and pH-Induced Disassembly of a Lysosomotropic Detergent: Impacts on Lysosomotropism and Lysosomal Delivery2016In: LANGMUIR, ISSN 0743-7463, Vol. 32, no 50, p. 13566-13575Article in journal (Refereed)
    Abstract [en]

    Lysosomotropic detergents (LDs) selectively rupture lysosomal membranes through mechanisms that have yet to be characterized. A consensus view, currently, holds that LDs, which are weakly basic, diffuse across cellular membranes as monomers in an uncharged state, and via protonation in the acidic lysosomal compartment, they become trapped, accumulate, and subsequently solubilize the membrane and induce lysosomal membrane permeabilization. Here we demonstrate that the lysosomotropic detergent O-methyl-serine dodecylamide hydrochloride (MSDH) spontaneously assembles into vesicles at, and above, cytosolic pH, and that the vesicles disassemble as the pH reaches 6.4 or lower. The aggregation commences at concentrations below the range of those used in cell studies. Assembly and disassembly of the vesicles was studied via dynamic light scattering, zeta potential measurements, cryo-TEM, and fluorescence correlation spectroscopy and was found to be reversible via control of the pH. Aggregation of MSDH into closed vesicles under cytosolic conditions is at variance with the commonly held view of LD behavior, and we propose that endocytotic pathways should be considered as possible routes of LD entry into lysosomes. We further demonstrate that MSDH vesicles can be loaded with fluorophores via a solution transition from low to high pH, for subsequent release when the pH is lowered again. The ability to encapsulate molecular cargo into MSDH vesicles together with its ability to disaggregate at low pH and to permeabilize the lysosomal membrane presents an intriguing possibility to use MSDH as a delivery system.

  • 3. Gunasekera, S.
    et al.
    Fernandes-Cerqueira, C.
    Wennmalm, Stefan
    KTH, School of Engineering Sciences (SCI), Applied Physics, Experimental Biomolecular Physics. KTH, Centres, Science for Life Laboratory, SciLifeLab.
    Wähämaa, H.
    Sommarin, Y.
    Catrina, A. I.
    Jakobsson, P. -J
    Göransson, U.
    Stabilized Cyclic Peptides as Scavengers of Autoantibodies: Neutralization of Anticitrullinated Protein/Peptide Antibodies in Rheumatoid Arthritis2018In: ACS Chemical Biology, ISSN 1554-8929, E-ISSN 1554-8937, Vol. 13, no 6, p. 1525-1535Article in journal (Refereed)
    Abstract [en]

    The occurrence of autoantibodies is a hallmark of rheumatoid arthritis, specifically those autoantibodies targeting proteins containing the arginine-derived amino acid citrulline. There is strong evidence showing that the occurrence of anticitrullinated protein/peptide antibodies (ACPA) are involved in disease progression, and ACPA was recently shown to induce pain in animals. Here, we explore a novel concept useful for research, diagnostics, and possibly therapy of autoimmune diseases, namely, to directly target and neutralize autoantibodies using peptide binders. A high-affinity peptide-based scavenger of ACPA was developed by grafting a citrullinated epitope derived from human fibrinogen into a naturally occurring stable peptide scaffold. The best scavenger comprises the truncated epitope α-fibrinogen, [Cit573]fib(566-580), grafted into the scaffold sunflower trypsin inhibitor-1, SFTI-1. The final peptide demonstrates low nanomolar apparent affinity and superior stability.

  • 4. Kronqvist, Nina
    et al.
    Otikovs, Martins
    Chmyrov, Volodymyr
    KTH, School of Engineering Sciences (SCI), Applied Physics, Experimental Biomolecular Physics.
    Chen, Gefei
    Andersson, Marlene
    Nordling, Kerstin
    Landreh, Michael
    Sarr, Médoune
    Jörnvall, Hans
    Wennmalm, Stefan
    Widengren, Jerker
    KTH, School of Engineering Sciences (SCI), Applied Physics, Experimental Biomolecular Physics.
    Meng, Qing
    Rising, Anna
    Otzen, Daniel Erik Rik
    Knight, Stefan
    Jaudzems, Kristaps
    Johansson, Jan Ove
    Sequential pH-driven dimerization and stabilization of the N-terminal domain enables rapid spider silk formation2014In: Nature Communications, ISSN 2041-1723, E-ISSN 2041-1723, Vol. 5, p. 3254-Article in journal (Refereed)
    Abstract [en]

    The mechanisms controlling the conversion of spider silk proteins into insoluble fibres, which happens in a fraction of a second and in a defined region of the silk glands, are still unresolved. The N-terminal domain changes conformation and forms a homodimer when pH is lowered from 7 to 6; however, the molecular details still remain to be determined. Here we investigate site-directed mutants of the N-terminal domain from Euprosthenops australis major ampullate spidroin 1 and find that the charged residues D40, R60 and K65 mediate intersubunit electrostatic interactions. Protonation of E79 and E119 is required for structural conversions of the subunits into a dimer conformation, and subsequent protonation of E84 around pH 5.7 leads to the formation of a fully stable dimer. These residues are highly conserved, indicating that the now proposed three-step mechanism prevents premature aggregation of spidroins and enables fast formation of spider silk fibres in general.

  • 5.
    Lakshmanan, Ramnath
    et al.
    KTH, School of Biotechnology (BIO), Industrial Biotechnology.
    Sanchez-Dominguez, Margarita
    Centro de Investigacion en Materials Avanzados (CIMAV) S.C., Mexico.
    Matutes-Aquino, Jose
    Centro de Investigacion en Materials Avanzados (CIMAV) S.C., Mexico.
    Wennmalm, Stefan
    KTH, School of Engineering Sciences (SCI), Applied Physics, Experimental Biomolecular Physics. KTH, Centres, Science for Life Laboratory, SciLifeLab.
    Kuttuva Rajarao, Gunaratna
    KTH, School of Biotechnology (BIO), Industrial Biotechnology.
    Removal of total organic carbon from sewage wastewater using poly(ethylenimine)-functionalized magnetic nanoparticles2014In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 30, no 4, p. 1036-1044Article in journal (Refereed)
    Abstract [en]

    The increased levels of organic carbon in sewage wastewater during recent years impose a great challenge to the existing wastewater treatment process (WWTP). Technological innovations are therefore sought that can reduce the release of organic carbon into lakes and seas. In the present study, magnetic nanoparticles (NPs) were synthesized, functionalized with poly(ethylenimine) (PEI), and characterized using TEM (transmission electron microscopy), X-ray diffraction (XRD), FTIR (Fourier transform infrared spectroscopy), CCS (confocal correlation spectroscopy), SICS (scattering interference correlation spectroscopy), magnetism studies, and thermogravimetric analysis (TGA). The removal of total organic carbon (TOC) and other contaminants using PEI-coated magnetic nanoparticles (PEI-NPs) was tested in wastewater obtained from the Hammarby Sjöstadsverk sewage plant, Sweden. The synthesized NPs were about 12 nm in diameter and showed a homogeneous particle size distribution in dispersion by TEM and CCS analyses, respectively. The magnetization curve reveals superparamagnetic behavior, and the NPs do not reach saturation because of surface anisotropy effects. A 50% reduction in TOC was obtained in 60 min when using 20 mg/L PEI-NPs in 0.5 L of wastewater. Along with TOC, other contaminants such as turbidity (89%), color (86%), total nitrogen (24%), and microbial content (90%) were also removed without significant changes in the mineral ion composition of wastewater. We conclude that the application of PEI-NPs has the potential to reduce the processing time, complexity, sludge production, and use of additional chemicals in the WWTP.

  • 6.
    Lizatovic, Robert
    et al.
    Lund Univ, Biochem & Struct Biol, POB 124, Lund, Sweden..
    Assent, Marvin
    Lund Univ, Biochem & Struct Biol, POB 124, Lund, Sweden..
    Barendregt, Arjan
    Univ Utrecht, Biomol Mass Spectrometry & Prote, Bijvoet Ctr Biomol Res, Padualaan 8, NL-3584 CH Utrecht, Netherlands.;Univ Utrecht, Utrecht Inst Pharmaceut Sci, Padualaan 8, NL-3584 CH Utrecht, Netherlands..
    Dahlin, Jonathan
    Lund Univ, Biochem & Struct Biol, POB 124, Lund, Sweden..
    Bille, Anna
    Lund Univ, Biochem & Struct Biol, POB 124, Lund, Sweden..
    Satzinger, Katharina
    Lund Univ, Biochem & Struct Biol, POB 124, Lund, Sweden..
    Tupina, Dagnija
    Lund Univ, Biochem & Struct Biol, POB 124, Lund, Sweden..
    Heck, Albert J. R.
    Univ Utrecht, Biomol Mass Spectrometry & Prote, Bijvoet Ctr Biomol Res, Padualaan 8, NL-3584 CH Utrecht, Netherlands.;Univ Utrecht, Utrecht Inst Pharmaceut Sci, Padualaan 8, NL-3584 CH Utrecht, Netherlands..
    Wennmalm, Stefan
    KTH, School of Engineering Sciences (SCI), Applied Physics, Experimental Biomolecular Physics. KTH, Centres, Science for Life Laboratory, SciLifeLab.
    Andre, Ingemar
    Lund Univ, Biochem & Struct Biol, POB 124, Lund, Sweden..
    A Protein-Based Encapsulation System with Calcium-Controlled Cargo Loading and Detachment2018In: Angewandte Chemie International Edition, ISSN 1433-7851, E-ISSN 1521-3773, Vol. 57, no 35, p. 11334-11338Article in journal (Refereed)
    Abstract [en]

    Protein-based encapsulation systems have a wide spectrum of applications in targeted delivery of cargo molecules and for chemical transformations in confined spaces. By engineering affinity between cargo and container proteins it has been possible to enable the efficient and specific encapsulation of target molecules. Missing in current approaches is the ability to turn off the interaction after encapsulation to enable the cargo to freely diffuse in the lumen of the container. Separation between cargo and container is desirable in drug delivery applications and in the use of capsids as catalytic nanoparticles. We describe an encapsulation system based on the hepatitisB virus capsid in which an engineered high-affinity interaction between cargo and capsid proteins can be modulated by Ca2+. Cargo proteins are loaded into capsids in the presence of Ca2+, while ligand removal triggers unbinding inside the container. We observe that confinement leads to hindered rotation of cargo inside the capsid. Application of the designed container for catalysis was also demonstrated by encapsulation of an enzyme with beta-glucosidase activity.

  • 7. Nagaraj, V.
    et al.
    Kazim, A. S.
    Helgeson, J.
    Lewold, C.
    Barik, S.
    Buda, P.
    Reinbothe, T. M.
    Wennmalm, Stefan
    KTH, School of Engineering Sciences (SCI), Applied Physics, Experimental Biomolecular Physics. KTH, Centres, Science for Life Laboratory, SciLifeLab.
    Zhang, E.
    Renström, E.
    Elevated basal insulin secretion in type 2 diabetes caused by reduced plasma membrane cholesterol2016In: Molecular Endocrinology, ISSN 0888-8809, E-ISSN 1944-9917, Vol. 30, no 10, p. 1059-1069Article in journal (Refereed)
    Abstract [en]

    Elevated basal insulin secretion under fasting conditions together with insufficient stimulated insulin release is an important hallmark of type 2 diabetes, but the mechanisms controlling basal insulin secretion remain unclear. Membrane rafts exist in pancreatic islet cells and spatially organize membrane ion channels and proteins controlling exocytosis, which may contribute to the regulation of insulin secretion. Membrane rafts (cholesterol and sphingolipid containing microdomains) were dramatically reduced in human type 2 diabetic and diabetic Goto-Kakizaki (GK) rat islets when compared with healthy islets. Oxidation of membrane cholesterol markedly reduced microdomain staining intensity in healthy human islets, but was without effect in type 2 diabetic islets. Intriguingly, oxidation of cholesterol affected glucose-stimulated insulin secretion only modestly, whereas basal insulin release was elevated. This was accompanied by increased intracellular Ca2+ spike frequency and Ca2+ influx and explained by enhanced single Ca2+ channel activity. These results suggest that the reduced presence of membrane rafts could contribute to the elevated basal insulin secretion seen in type 2 diabetes.

  • 8.
    Navarro, Julien R. G.
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
    Wennmalm, Stefan
    KTH, School of Engineering Sciences (SCI), Applied Physics. KTH, Centres, Science for Life Laboratory, SciLifeLab.
    Godfrey, Jamie
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
    Breitholtz, Magnus
    Edlund, Ulrica
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
    Luminescent Nanocellulose Platform: From Controlled Graft Block Copolymerization to Biomarker Sensing2016In: Biomacromolecules, ISSN 1525-7797, E-ISSN 1526-4602, Vol. 17, no 3, p. 1101-1109Article in journal (Refereed)
    Abstract [en]

    A strategy is devised for the conversion of cellulose nanofibrils (CNF) into fluorescently labeled probes involving the synthesis of CNF-based macroinitiators that initiate radical polymerilation of methyl acrylate and acrylic acid N-hydroxysuccinimide ester producing a graft block copolymer modified CNF. Finally, a luminescent probe (Lucifer yellow derivative) was labeled onto the modified CNF through an amidation reaction. The surface modification steps were :verified with solid-state C-13 nuclear magnetic resonance (NMR) and Fourier transform infrared spectroscopy. Fluorescence correlation spectroscopy (FCS) confirmed the successful labeling of the CNF; the CNF have a hydrodynamic radius of about 700 nm with an average number of dye molecules per fibril of at least 6600. The modified CNF was also imaged with confocal laser scanning microscopy. Luminescent CNF proved to be viable biomarkers and allow for fluorescence-based optical detection of CNF uptake and distribution in organisms such as crustaceans. The luminescent CNF were exposed to live juvenile daphnids and microscopy analysis revealed the presence of the luminescent CNF all over D. magna's alimentary canal tissues without any toxicity effect leading to the death of the specimen.

  • 9.
    Paulraj, Thomas
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology.
    Wennmalm, Stefan
    KTH, School of Engineering Sciences (SCI), Applied Physics, Experimental Biomolecular Physics. KTH, Centres, Science for Life Laboratory, SciLifeLab. ..
    Riazanova, Anastasia, V
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology.
    Wu, Qiong
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology.
    Crespo, Gaston A.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Applied Physical Chemistry.
    Svagan, Anna J.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology.
    Porous Cellulose Nanofiber-Based Microcapsules for Biomolecular Sensing2018In: ACS Applied Materials and Interfaces, ISSN 1944-8244, E-ISSN 1944-8252, Vol. 10, no 48, p. 41146-41154Article in journal (Refereed)
    Abstract [en]

    Cellulose nanofibers (CNFs) have recently attracted a lot of attention in sensing because of their multifunctional character and properties such as renewability, nontoxicity, biodegradability, printability, and optical transparency in addition to unique physicochemical, barrier, and mechanical properties. However, the focus has exclusively been devoted toward developing two-dimensional sensing platforms in the form of nanopaper or nanocellulose-based hydrogels. To improve the flexibility and sensing performance in situ, for example, to detect biomarkers in vivo for early disease diagnostics, more advanced CNF-based structures are needed. Here, we developed porous and hollow, yet robust, CNF-based microcapsules using only the primary plant cell wall components, CNF, pectin, and xyloglucan, to assemble the capsule wall. The fluorescein isothiocyanate-labeled dextrans with M-w of 70 and 2000 kDa could enter the hollow capsules at a rate of 0.13 +/- 0.04 and 0.014 +/- 0.009 s(-1), respectively. This property is very attractive because it minimizes the influence of mass transport through the capsule wall on the response time. As a proof of concept, glucose oxidase (GOx) enzyme was loaded (and cross-linked) in the microcapsule interior with an encapsulation efficiency of 68 +/- 2%. The GOx-loaded microcapsules were immobilized on a variety of surfaces (here, inside a flow channel, on a carbon-coated sensor or a graphite rod) and glucose concentrations up to 10 mM could successfully be measured. The present concept offers new opportunities in the development of simple, more efficient, and disposable nanocellulose-based analytical devices for several sensing applications including environmental monitoring, healthcare, and diagnostics.

  • 10.
    Paulraj, Thomas
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Polymeric Materials.
    Wennmalm, Stefan
    KTH, School of Engineering Sciences (SCI), Applied Physics. KTH, Centres, Science for Life Laboratory, SciLifeLab.
    Wieland, D.C. Florian
    Dédinaité, Andra
    KTH, Superseded Departments (pre-2005), Chemistry.
    Pomorski, T. Günther
    Cárdenas, M.
    Svagan, Anna Justina
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology.
    Assembly of Primary Cell-Wall inspired Microcontainers, Plantosomes, as a step towards a Synthetic Plant-CellManuscript (preprint) (Other academic)
  • 11. Rabasovic, M. D.
    et al.
    Sisamakis, Evangelos
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Wennmalm, Stefan
    KTH, School of Engineering Sciences (SCI), Applied Physics. KTH, Centres, Science for Life Laboratory, SciLifeLab.
    Widengren, Jerker
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Label-Free Fluctuation Spectroscopy Based on Coherent Anti-Stokes Raman Scattering from Bulk Water Molecules2016In: ChemPhysChem, ISSN 1439-4235, E-ISSN 1439-7641, Vol. 17, no 7, p. 1025-1033Article in journal (Refereed)
    Abstract [en]

    Nanoparticles (NPs) and molecules can be analyzed by inverse fluorescence correlation spectroscopy (iFCS) as they pass through an open detection volume, displacing fractions of the fluorescence-emitting solution in which they are dissolved. iFCS does not require the NPs or molecules to be labeled. However, fluorophores in m-mm concentrations are needed for the solution signal. Here, we instead use coherent anti-Stokes Raman scattering (CARS) from plain water molecules as the signal from the solution. By this fully label-free approach, termed inverse CARS-based correlation spectroscopy (iCARS-CS), NPs that are a few tenths of nm in diameter and at pM concentrations can be analyzed, and their absolute volumes/concentrations can be determined. Likewise, lipid vesicles can be analyzed as they diffuse/flow through the detection volume by using CARS fluctuations from the surrounding water molecules. iCARS-CS could likely offer a broadly applicable, label-free characterization technique of, for example, NPs, small lipid exosomes, or microparticles in biomolecular diagnostics and screening, and can also utilize CARS signals from biologically relevant media other than water.

  • 12. Sandén, Tor
    et al.
    Wyss, Romain
    Santschi, Christian
    Hassaine, Gherici
    Deluz, Cedric
    Martin, Olivier J. F.
    Wennmalm, Stefan
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Vogel, Horst
    A Zeptoliter Volume Meter for Analysis of Single Protein Molecules2012In: Nano letters (Print), ISSN 1530-6984, E-ISSN 1530-6992, Vol. 12, no 1, p. 370-375Article in journal (Refereed)
    Abstract [en]

    A central goal in bioanalytics is to determine the concentration of and interactions between biomolecules. Nanotechnology allows performing such analyses in a highly parallel, low-cost, and miniaturized fashion. Here we report on label-free volume, concentration, and mobility analysis of single protein molecules and nanoparticles during their diffusion through a subattoliter detection volume, confined by a 100 nm aperture in a thin gold film. A high concentration of small fluorescent molecules renders the aqueous solution in the aperture brightly fluorescent. Nonfluorescent analytes diffusing into the aperture displace the fluorescent molecules in the solution, leading to a decrease of the detected fluorescence signal, while analytes diffusing out of the aperture return the fluorescence level. The resulting fluorescence fluctuations provide direct information on the volume, concentration, and mobility of the nonfluorescent analytes through fluctuation analysis in both time and amplitude.

  • 13.
    Shelke, Ganesh Vilas
    et al.
    Univ Gothenburg, Sahlgrenska Acad, Krefting Res Ctr, Inst Med, Gothenburg, Sweden.;Univ Gothenburg, Sahlgrenska Acad, Inst Clin Sci, Dept Surg, Gothenburg, Sweden..
    Yin, Yanan
    Univ Gothenburg, Sahlgrenska Acad, Krefting Res Ctr, Inst Med, Gothenburg, Sweden.;Shanghai Jiao Tong Univ, Sch Med, Dept Biochem & Mol Cell Biol, Shanghai, Peoples R China..
    Jang, Su Chul
    Univ Gothenburg, Sahlgrenska Acad, Krefting Res Ctr, Inst Med, Gothenburg, Sweden..
    Lasser, Cecilia
    Univ Gothenburg, Sahlgrenska Acad, Krefting Res Ctr, Inst Med, Gothenburg, Sweden..
    Wennmalm, Stefan
    KTH, School of Engineering Sciences (SCI), Applied Physics. KTH, Centres, Science for Life Laboratory, SciLifeLab.
    Hoffmann, Hans Jurgen
    Aarhus Univ, Dept Clin Med, Aarhus, Denmark.;Aarhus Univ Hosp, Dept Resp & Allergy, Aarhus, Denmark..
    Li, Li
    Shanghai Jiao Tong Univ, Shanghai Peoples Hosp 1, Dept Lab Med, Shanghai, Peoples R China..
    Gho, Yong Song
    Pohang Univ Sci & Technol, Dept Life Sci, Pohang, South Korea..
    Nilsson, Jonas Andreas
    Univ Gothenburg, Sahlgrenska Acad, Inst Clin Sci, Dept Surg, Gothenburg, Sweden..
    Lotvall, Jan
    Univ Gothenburg, Sahlgrenska Acad, Krefting Res Ctr, Inst Med, Gothenburg, Sweden..
    Endosomal signalling via exosome surface TGF beta-12019In: Journal of Extracellular Vesicles, ISSN 2001-3078, E-ISSN 2001-3078, Vol. 8, no 1, article id 1650458Article in journal (Refereed)
    Abstract [en]

    Extracellular vesicles such as exosomes convey biological messages between cells, either by surface-to-surface interaction or by shuttling of bioactive molecules to a recipient cell's cytoplasm. Here we show that exosomes released by mast cells harbour both active and latent transforming growth factor beta-1 (TGF beta-1) on their surfaces. The latent form of TGF beta-1 is associated with the exosomes via heparinase-II and pH-sensitive elements. These vesicles traffic to the endocytic compartment of recipient human mesenchymal stem cells (MSCs) within 60 min of exposure. Further, the exosomes-associated TGF beta-1 is retained within the endosomal compartments at the time of signalling, which results in prolonged cellular signalling compared to free-TGF beta-1. These exosomes induce a migratory phenotype in primary MSCs involving SMAD-dependent pathways. Our results show that mast cell-derived exosomes are decorated with latent TGF beta-1 and are retained in recipient MSC endosomes, influencing recipient cell migratory phenotype. We conclude that exosomes can convey signalling within endosomes by delivering bioactive surface ligands to this intracellular compartment.

  • 14. Vogel, H.
    et al.
    Sandén, T.
    Wyss, R.
    Wennmalm, Stefan
    KTH, School of Engineering Sciences (SCI), Applied Physics, Experimental Biomolecular Physics.
    Probing bio-molecular interactions in attoliter volumes2014In: Optical Sensors, 2014, 2014Conference paper (Refereed)
    Abstract [en]

    We report on label-free volume, concentration, and mobility analysis of single protein molecules and nanoparticles during their diffusion through a subattoliter detection volume, confined by a 100 nm aperture in a thin gold film. A high concentration of small fluorescent molecules renders the aqueous solution in the aperture brightly fluorescent. Nonfluorescent analytes diffusing into the aperture displace the fluorescent molecules in the solution, leading to a decrease of the detected fluorescence signal, while analytes diffusing out of the aperture return the fluorescence level. The resulting fluorescence fluctuations provide direct information on the volume, concentration, and mobility of the nonfluorescent analytes through fluctuation analysis in both time and amplitude.

  • 15.
    Wennmalm, Stefan
    KTH, School of Engineering Sciences (SCI), Applied Physics. KTH, Centres, Science for Life Laboratory, SciLifeLab.
    Potentials and pitfalls of inverse fluorescence correlation spectroscopy2018In: Methods, ISSN 1046-2023, E-ISSN 1095-9130, Vol. 140, p. 23-31Article in journal (Refereed)
    Abstract [en]

    Inverse Fluorescence Correlation Spectroscopy (iFCS) is a variant of FCS where unlabeled particles in solution, or domains in membranes, displace their surrounding, signal-generating molecules and thereby generate fluctuations. iFCS has to date been applied to unlabeled as well as labeled particles and protein molecules, using fluorescence as well as Raman scattering as a signal source, in diffraction-limited detection volumes as well as in nano-wells, and on fixed surfaces as well as in lipid bilayers. This review describes these applications and discusses the potentials and pitfalls when using iFCS.

  • 16. Wennmalm, Stefan
    et al.
    Blom, Hans
    Wallerman, Lennart
    Rigler, Rudolf
    UV-Fluorescence Correlation Spectroscopy of 2-Aminopurine2001In: Biological chemistry (Print), ISSN 1431-6730, E-ISSN 1437-4315, Vol. 382, no 3, p. 393-397Article in journal (Refereed)
    Abstract [en]

    We have built a fluorescence correlation spectroscopy (FCS) microscope for ultraviolet excitation (280 300 nm) and emission. With UV excitation the fluorescence of natural fluorophores such as the modified nucleotide 2-aminopurine can be analyzed. The sensitivity of a natural fluorophore toward conformational changes can reveal dynamics in biomolecules. UVFCS is well suited for detection of intensity fluctuations related to such conformational dynamics. Here we show UVFCS measured on pQuarterphenyl and on 2-aminopurine (2-AP). The triplet state rate constants and the excitation cross section for 2- AP were estimated to k[23]=1 x 10[6] s[-1], k[31]=3 x 10[5] s[-1], and σ=2 x 10[-17] cm[2].

  • 17.
    Wennmalm, Stefan
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Experimental Biomolecular Physics. KTH, Centres, Science for Life Laboratory, SciLifeLab.
    Chmyrov, Volodymyr
    KTH, School of Engineering Sciences (SCI), Applied Physics, Experimental Biomolecular Physics.
    Widengren, Jerker
    KTH, School of Engineering Sciences (SCI), Applied Physics, Experimental Biomolecular Physics.
    Tjernberg, Lars
    Highly Sensitive FRET-FCS Detects Amyloid beta-Peptide Oligomers in Solution at Physiological Concentrations2015In: Analytical Chemistry, ISSN 0003-2700, E-ISSN 1520-6882, Vol. 87, no 23, p. 11700-11705Article in journal (Refereed)
    Abstract [en]

    Oligomers formed by the amyloid beta-peptide (A beta) are pathogens in Alzheimers disease. Increased knowledge on the oligomerization process is crucial for understanding the disease and for finding treatments. Ideally, A beta oligomerization should be studied in solution and at physiologically relevant concentrations, but most popular techniques of today are not capable of such analyses. We demonstrate here that the combination of FOrster Resonance Energy Transfer and Fluorescence Correlation Spectroscopy (FRET-FCS) has a unique ability to detect small subpopulations of FRET-active molecules and oligomers. FRET-FCS could readily detect a FRET-active oligonucleotide present at levels as low as 0.5% compared to FRET-inactive dye molecules. In contrast, three established fluorescence fluctuation techniques (FCS, FCCS, and PCH) required fractions between 7 and 11%. When applied to the analysis of A beta, FRET-FCS detected oligomers consisting of less than 10 A beta molecules, which coexisted with the monomers at fractions as low as 2 +/- 2%. Thus, we demonstrate for the first time direct detection of small fractions of A beta oligomers in solution at physiological concentrations. This ability of FRET-FCS could be an indispensable tool for studying biological oligomerization processes, in general, and for finding therapeutically useful oligomerization inhibitors.

  • 18. Wennmalm, Stefan
    et al.
    Edman, Lars
    Rigler, Rudolf
    Conformational fluctuations in single DNA molecules1997In: Proceedings of the National Academy of Sciences of the United States of America, ISSN 0027-8424, E-ISSN 1091-6490Article in journal (Refereed)
  • 19. Wennmalm, Stefan
    et al.
    Edman, Lars
    Rigler, Rudolf
    Non-ergodic behaviour in conformational transitions of single DNA molecules1999In: Chemical Physics, ISSN 0301-0104, E-ISSN 1873-4421, Chemical PhysicsArticle in journal (Refereed)
  • 20. Wennmalm, Stefan
    et al.
    Rigler, Rudolf
    On Death Numbers and Survival Times of Single Dye Molecules1999In: Journal of Physical Chemistry B, ISSN 1520-6106, E-ISSN 1520-5207Article in journal (Refereed)
  • 21.
    Wennmalm, Stefan
    et al.
    Laboratory of Cellular Biophysics, Rockefeller University, New York, USA.
    Simon, Sanford M.
    Laboratory of Cellular Biophysics, Rockefeller University, New York, USA.
    Studying Individual Events in Biology2007In: Annual Review of Biochemistry, ISSN 0066-4154, E-ISSN 1545-4509, Vol. 76, p. 419-446Article in journal (Refereed)
    Abstract [en]

    Studying the properties of individual events and molecules offers a host of advantages over taking only macroscopic measurements of populations. Here we review such advantages, as well as some pitfalls, focusing on examples from biological imaging. Examples include single proteins, their interactions in cells, organelles, and their interactions both with each other and with parts of the cell. Additionally, we discuss constraints that limit the study of single events, along with the criteria that must be fulfilled to determine whether single molecules or events are being detected.

  • 22.
    Wennmalm, Stefan
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Experimental Biomolecular Physics.
    Thyberg, Per
    KTH, School of Engineering Sciences (SCI), Applied Physics, Experimental Biomolecular Physics.
    Xu, Lei
    KTH, School of Engineering Sciences (SCI), Applied Physics, Experimental Biomolecular Physics.
    Widengren, Jerker
    KTH, School of Engineering Sciences (SCI), Applied Physics, Experimental Biomolecular Physics.
    Inverse-Fluorescence Correlation Spectroscopy2009In: Analytical Chemistry, ISSN 0003-2700, E-ISSN 1520-6882, Vol. 81, no 22, p. 9209-9215Article in journal (Refereed)
    Abstract [en]

    An alternative version of fluorescence correlation spectroscopy is presented, where the signal from a medium surrounding the particles of interest is analyzed, as opposed to a signal from the particles themselves. Ibis allows for analysis of unlabeled particles and potentially of biomolecules. Here, the concept together with principal experiments on polystyrene beads of 100, 200, 400, and 800 nm diameter in an aqueous solution of alexa 488-fluorophores are presented. The use of photo detectors allowing higher photon fluxes, or of reduced detection volumes, should enable analysis of significantly smaller particles or even biomolecules.

  • 23.
    Wennmalm, Stefan
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Widengren, Jerker
    KTH, School of Engineering Sciences (SCI), Applied Physics, Experimental Biomolecular Physics.
    Interferometry and fluorescence detection for simultaneous analysis of labeled and unlabeled nanoparticles in solution2012In: Journal of the American Chemical Society, ISSN 0002-7863, E-ISSN 1520-5126, Vol. 134, no 48, p. 19516-19519Article in journal (Refereed)
    Abstract [en]

    A novel fluctuation spectroscopy technique based on interferometry is described. The technique, termed scattering interference correlation spectroscopy (SICS), autocorrelates the signals from the forward-scattered and transmitted laser light from nanoparticles (NPs) in solution. SICS has two important features: First, for unlabeled NPs with known refractive index, it analyzes not only the diffusion coefficient but also the effective cross section and concentration in a single measurement. Second, it can be combined with fluorescence correlation spectroscopy (FCS) for simultaneous analysis of labeled and unlabeled NPs. SICS is here demonstrated on unlabeled M13 phages and on unlabeled NPs with diameters of 210 nm down to 26 nm. It is also shown how the combination of SICS and FCS can be used to determine the fraction of fluorescent NPs in a mixture and estimate Kd from a single binding measurement.

  • 24.
    Wennmalm, Stefan
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Experimental Biomolecular Physics.
    Widengren, Jerker
    KTH, School of Engineering Sciences (SCI), Applied Physics, Experimental Biomolecular Physics.
    Inverse-fluorescence correlation spectroscopy: more information and less labeling2011In: Frontiers in Bioscience, ISSN 1093-9946, E-ISSN 1093-4715, Vol. s3, p. 385-392Article in journal (Refereed)
    Abstract [en]

    Inverse-Fluorescence Correlation Spectroscopy(iFCS) is a recently developed modification of standardFCS that allows analysis of particles and biomoleculeswithout labeling. The particles generate no signal; insteadthe signal is generated by a surrounding medium. Particlesdiffusing through the FCS-detection volume displace afraction of the surrounding medium, causing transient dipsin the detected signal. These give information about themobility and concentration of the analyzed particles. Alsolabeled particles can be analyzed, whereby their signal iscross-correlated with that from the surrounding medium(iFCCS). This can give information about the volume of thelabeled particles, or alternatively about the size of thedetection volume. Also the interaction of unlabeledparticles with small, labeled ligands can be analyzed withiFCCS. This allows using cross-correlation as a sensitiveindication of binding, even though only one binding-partneris labeled. This review describes the principles of iFCS andiFCCS and measurements of microspheres dissolved in asurrounding medium containing alexa 488. We also discusspractical considerations, and future possibilities foranalyses of biomolecules.

  • 25.
    Wennmalm, Stefan
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Experimental Biomolecular Physics.
    Widengren, Jerker
    KTH, School of Engineering Sciences (SCI), Applied Physics, Experimental Biomolecular Physics.
    Inverse-Fluorescence Cross-Correlation Spectroscopy2010In: Analytical Chemistry, ISSN 0003-2700, E-ISSN 1520-6882, Vol. 82, no 13, p. 5646-5651Article in journal (Refereed)
    Abstract [en]

    Inverse-fluorescence correlation spectroscopy (iFCS) was recently introduced as an alternative version of FCS that does not require labeling of the analyzed particles or biomolecules. In iFCS, the signal from a medium surrounding the particles is analyzed, as opposed to a signal from the studied particles themselves. As unlabeled particles diffuse through the detection volume, they displace a fraction of the fluorescent medium, causing transient dips in the detected signal which give information about the mobility and concentration of the analyzed particles. Here inverse-fluorescence cross-correlation spectroscopy (iFCCS) is introduced as an extension of iFCS. In iFCCS, labeled particles/biomolecules are analyzed and their fluorescence signal is cross-correlated with the signal from the surrounding medium. When labeled particles are analyzed, a direct estimate of the volume of the particles is obtained or, alternatively, an estimate of the size of the detection volume. Another possibility is to analyze the interaction of small, labeled molecules with unlabeled particles, resulting in cross-correlation as an indication of binding, even though only one binding partner is labeled. This also enables accurate estimation of the degree of labeling, since the amounts of labeled and unlabeled particles are estimated independently.

  • 26. Wyss, Romain
    et al.
    Sandén, Tor
    Piguet, Joachim
    Santschi, Christian
    Hassaine, Gherici
    Deluz, Cedric
    Martin, Olivier J. F.
    Wennmalm, Stefan
    KTH, School of Engineering Sciences (SCI), Applied Physics, Experimental Biomolecular Physics.
    Vogel, Horst
    Subwavelength Metal Apertures for Label-Free Detection of Single-Molecules2012In: Biophysical Journal, ISSN 0006-3495, E-ISSN 1542-0086, Vol. 102, no 3, p. 727A-727AArticle in journal (Other academic)
1 - 26 of 26
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