Abstract:
:An approach is described using fluorescence resonance energy transfer (FRET) to detect inhomogeneity in lipid organization, on distance scales of the order of tens of nanometers or greater, in lipid bilayers. This approach compares the efficiency of energy transfer between two matched fluorescent lipid donors, differing in their affinities for ordered versus disordered regions of the bilayer, and an acceptor lipid that distributes preferentially into disordered regions. Inhomogeneities in bilayer organization, on spatial scales of tens of nanometers or greater, are detected as a marked difference in the efficiencies of quenching of fluorescence of the two donor species by the acceptor. Using a novel pair of 7-nitrobenz-2-oxa-1,3-diazol-4-yl (NBD)-labeled tetraacyl lipids as donor species with a rhodaminyl-labeled acceptor, this strategy faithfully reports homo- versus inhomogeneous mixing in each of several lipid bilayer systems whose organization on the FRET distance scale can be predicted from previous findings. Interestingly, however, the present FRET method reports clear evidence of inhomogeneity in the organization of mixtures combining sphingomyelin or saturated phospholipids with unsaturated phospholipids and physiological proportions of cholesterol, even at physiological temperatures where these systems have been reported to appear homogeneous by fluorescence microscopy. These results indicate that under physiological conditions, lipid mixtures mimicking the lipid composition of the outer leaflet of the plasma membrane can form domains on a spatial scale comparable to that inferred for the dimensions of lipid rafts in biological membranes.
journal_name
Biophys Jjournal_title
Biophysical journalauthors
Silvius JRdoi
10.1016/S0006-3495(03)74542-1subject
Has Abstractpub_date
2003-08-01 00:00:00pages
1034-45issue
2eissn
0006-3495issn
1542-0086pii
S0006-3495(03)74542-1journal_volume
85pub_type
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