Document Detail

Single-molecule microscopy on model membranes reveals anomalous diffusion.
MedLine Citation:
PMID:  9251823     Owner:  NLM     Status:  MEDLINE    
The lateral mobility of lipids in phospholipid membranes has attracted numerous experimental and theoretical studies, inspired by the model of Singer and Nicholson (1972. Science, 175:720-731) and the theoretical description by Saffman and Delbrück (1975. Proc. Natl. Acad. Sci. USA. 72:3111-3113). Fluorescence recovery after photobleaching (FRAP) is used as the standard experimental technique for the study of lateral mobility, yielding an ensemble-averaged diffusion constant. Single-particle tracking (SPT) and the recently developed single-molecule imaging techniques now give access to data on individual displacements of molecules, which can be used for characterization of the mobility in a membrane. Here we present a new type of analysis for tracking data by making use of the probability distribution of square displacements. The potential of this new type of analysis is shown for single-molecule imaging, which was employed to follow the motion of individual fluorescence-labeled lipids in two systems: a fluid-supported phospholipid membrane and a solid polymerstabilized phospholipid monolayer. In the fluid membrane, a high-mobility component characterized by a diffusion constant of 4.4 microns2/s and a low-mobility component characterized by a diffusion constant of 0.07 micron2/s were identified. It is proposed that the latter characterizes the so-called immobile fraction often found in FRAP experiments. In the polymer-stabilized system, diffusion restricted to corrals of 140 nm was directly visualized. Both examples show the potentials of such detailed analysis in combination with single-molecule techniques: with minimal interference with the native structure, inhomogeneities of membrane mobility can be resolved with a spatial resolution of 100 nm, well below the diffraction limit.
G J Schütz; H Schindler; T Schmidt
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  Biophysical journal     Volume:  73     ISSN:  0006-3495     ISO Abbreviation:  Biophys. J.     Publication Date:  1997 Aug 
Date Detail:
Created Date:  1997-09-29     Completed Date:  1997-09-29     Revised Date:  2010-09-13    
Medline Journal Info:
Nlm Unique ID:  0370626     Medline TA:  Biophys J     Country:  UNITED STATES    
Other Details:
Languages:  eng     Pagination:  1073-80     Citation Subset:  IM    
Institute for Biophysics, University of Linz, Austria.
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MeSH Terms
Dimyristoylphosphatidylcholine / chemistry*
Fluorescent Dyes
Lipid Bilayers / chemistry*
Liposomes / chemistry*
Microscopy, Fluorescence / methods
Models, Chemical
Molecular Conformation
Phosphatidylcholines / chemistry*
Phosphatidylethanolamines / chemistry*
Rhodamines / chemistry*
Sensitivity and Specificity
Reg. No./Substance:
0/Fluorescent Dyes; 0/Lipid Bilayers; 0/Liposomes; 0/Phosphatidylcholines; 0/Phosphatidylethanolamines; 0/Rhodamines; 0/triethylammonium N-(6-tetramethylrhodaminethiocarbamoyl)-1,2-dihexadecanoyl-sn-glycero-3-phosphoethanolamine; 13699-48-4/Dimyristoylphosphatidylcholine; 4158-89-8/tetramethylrhodamine isothiocyanate; 6753-55-5/1-palmitoyl-2-oleoylphosphatidylcholine

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