Fluid-fluid membrane microheterogeneity: A fluorescence resonance energy transfer study

被引:103
作者
Loura, LMS [1 ]
Fedorov, A
Prieto, M
机构
[1] Inst Super Tecn, Ctr Quim Fis Mol, P-1049001 Lisbon, Portugal
[2] Univ Evora, Dept Quim, P-7000671 Evora, Portugal
关键词
D O I
10.1016/S0006-3495(01)76057-2
中图分类号
Q6 [生物物理学];
学科分类号
071011 ;
摘要
Large unilamellar vesicles of dimyristoylphosphatidylcholine/cholesterol mixtures were studied using fluorescence techniques (steady-state fluorescence intensity and anisotropy, fluorescence lifetime, and fluorescence resonance energy transfer (FRET)). Three compositions (cholesterol mole fraction 0.15, 0.20, and 0.25) and two temperatures (30 and 40 degreesC) inside the coexistence range of liquid-ordered (I,) and liquid-disordered (I,) phases were investigated. Two common membrane probes, N-(7-nitrobenz-2-oxa-1,3-diazol-4-yl)-dimyristoylphosphatidylethanolamine (NBD-DMPE) and N-(lissamine(TM)-rhodamine B)-dimyristoylphosphatidylethanolamine (Rh-DMPE), which form a FRET pair, were used. The 1(o)/1(d) partition coefficients of the probes were determined by individual photophysical measurements and global analysis of time-resolved FRET decays. Although the acceptor, Rh-DMPE, prefers the I, phase, the opposite is observed for the donor, NBD-DMPE. Accordingly, FRET efficiency decreases as a consequence of phase separation. Comparing the independent measurements of partition coefficient, it was possible to detect very small domains (<20 nm) of I, in the cholesterol-poor end of the phase coexistence range. In contrast, domains of I, in the cholesterol-rich end of the coexistence range have comparatively large size. These observations are probably related to different processes of phase separation, nucleation being preferred in formation of I, phase from initially pure I,, and domain growth being faster in formation of I, phase from
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页码:776 / 788
页数:13
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