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Fluorescence correlation spectroscopy diffusion laws in the presence of moving nanodomains
KTH, School of Engineering Sciences (SCI), Applied Physics, Experimental Biomolecular Physics.
KTH, School of Engineering Sciences (SCI), Applied Physics, Experimental Biomolecular Physics.ORCID iD: 0000-0003-3200-0374
2016 (English)In: Journal of Physics D: Applied Physics, ISSN 0022-3727, E-ISSN 1361-6463, Vol. 49, no 11, article id 114002Article in journal (Refereed) Published
Resource type
Text
Abstract [en]

It has been shown by means of simulations that spot variation fluorescence correlation spectroscopy (sv-FCS) can be used for the identification and, to some extent, also characterization of immobile lipid nanodomains in model as well as cellular plasma membranes. However, in these simulations, the nanodomains were assumed to be stationary, whereas they actually tend to move like the surrounding lipids. In the present study, we investigated how such domain movement influences the diffusion time/spot-size dependence observed in FCS experiments, usually referred to as 'diffusion law' analysis. We show that domain movement might mask the effects of the 'anomalous' diffusion characteristics of membrane lipids or proteins predicted for stationary domains, making it difficult to identify such moving nanodomains by sv-FCS. More specifically, our simulations indicate that (i) for domains moving up to a factor of 2.25 slower than the surrounding lipids, such impeded diffusion cannot be observed and the diffusion behaviour of the proteins or lipids is indistinguishable from that of freely diffusing molecules, i.e. nanodomains are not detected; (ii) impeded protein/lipid diffusion behaviour can be observed in experiments where the radii of the detection volume are similar in size to the domain radii, the domain diffusion is about 10 times slower than that of the lipids, and the probes show a high affinity to the domains; and (iii) presence of nanodomains can only be reliably detected by diffraction limited sv-FCS when the domains move very slowly (about 200 times slower than the lipid diffusion). As nanodomains are expected to be in the range of tens of nanometres and most probes show low affinities to such domains, sv-FCS is limited to stationary domains and/or STED-FCS. However, even for that latter technique, diffusing domains smaller than 50 nm in radius are hardly detectable by FCS diffusion time/spot-size dependencies.

Place, publisher, year, edition, pages
Institute of Physics Publishing (IOPP), 2016. Vol. 49, no 11, article id 114002
Keywords [en]
FCS, lipid nanodomains, anomalous diffusion, STED, spot-variation FCS
National Category
Physical Sciences
Identifiers
URN: urn:nbn:se:kth:diva-184015DOI: 10.1088/0022-3727/49/11/114002ISI: 000371007100003Scopus ID: 2-s2.0-84960096929OAI: oai:DiVA.org:kth-184015DiVA, id: diva2:914568
Note

QC 20160324

Available from: 2016-03-24 Created: 2016-03-22 Last updated: 2019-04-04Bibliographically approved
In thesis
1. Super resolution fluorescence imaging: analyses, simulations and applications
Open this publication in new window or tab >>Super resolution fluorescence imaging: analyses, simulations and applications
2019 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Fluorescence methods offer extraordinary sensitivity and specificity, and are extensively used in the life sciences. In recent years, super resolution fluorescence imaging techniques have developed strongly, uniquely combining ~10 nm sub diffraction resolution and specific labeling with high efficiency. This thesis explores this potential, with a major focus on Stimulated Emission Depletion, STED, microscopy, applications thereof, image analyses and simulation studies. An additional theme in this thesis is development and use of single molecule fluorescence correlation spectroscopy, FCS, and related techniques, as tools to study dynamic processes at the molecular level. In paper I the proteins cytochrome-bo3 and ATP-synthase are studied with fluorescence cross-correlation spectroscopy, FCCS. These two proteins are a part of the energy conversion process in E. coli, converting ADP into ATP. We found that an increased interaction between these proteins, detected by FCCS, correlates with an increase in the ATP production. In paper II an FCS-based imaging method is developed, capable to determine absolute sizes of objects, smaller than the resolution limit of the microscope used. Combined with STED, this may open for studies of membrane nano-domains, such as those investigated by simulations in paper VII. In paper III and paper IV super resolution STED imaging was applied on Streptococcus Pneumoniae, revealing information about function and distribution of proteins involved in the defense mechanism of the bacteria, as well as their role in bacterial meningitis. In paper V, we used STED imaging to investigate protein distributions in platelets. We then found that the adhesion protein P-selectin changes its distribution pattern in platelets incubated with tumor cells, and with machine learning algorithms and classical image analysis of the STED images it is possible to automatically distinguish such platelets from platelets activated by other means. This could provide a strategy for minimally invasive diagnostics of early cancer development, and deeper understanding of the role of platelets in cancer development. Finally, this thesis presents Monte-Carlo simulations of biological processes and their monitoring by FCS. In paper VI, a combination of FCCS and simulations was applied to resolve the interactions between a transcription factor (p53) and an oncoprotein (MDM2) inside live cells. In paper VII, the feasibility of FCS techniques for studying nano-domains in membranes is investigated purely by simulations, identifying the conditions under which such nano-domains would be possible to detect by FCS. In paper VIII, proton exchange dynamics at biological membranes were simulated in a model, verifying experimental FCS data and identifying fundamental mechanisms by which membranes mediate proton exchange on a local (~10nm) scale.

Place, publisher, year, edition, pages
KTH Royal Institute of Technology, 2019. p. 81
Series
TRITA-SCI-FOU ; 2019:20
National Category
Other Physics Topics
Research subject
Physics
Identifiers
urn:nbn:se:kth:diva-248297 (URN)978-91-7873-171-8 (ISBN)
Public defence
2019-04-26, FA32, KTH, Roslagstullsbacken 21, Stockholm, 18:22 (English)
Opponent
Supervisors
Note

QC 20190405

Available from: 2019-04-05 Created: 2019-04-04 Last updated: 2019-04-05Bibliographically approved

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