Solubility of amphiphiles in membranes: influence of phase properties and amphiphile head group

被引:24
作者
Estronca, LMBB
Moreno, MJ
Abreu, MSC
Melo, E
Vaz, WLC [1 ]
机构
[1] Univ Coimbra, Dept Quim, P-3004535 Coimbra, Portugal
[2] Univ Nova Lisboa, Inst Tecnol Quim & Biol, P-2784505 Oeiras, Portugal
[3] Inst Super Tecn, P-1049001 Lisbon, Portugal
关键词
fluorescent lipid amphiphiles; amphiphile aggregation; membrane phases; phase partitioning; dipolar surface potential;
D O I
10.1016/S0006-291X(02)00905-1
中图分类号
Q5 [生物化学]; Q7 [分子生物学];
学科分类号
071010 ; 081704 ;
摘要
The solubilities of two fluorescent lipid amphiphiles with comparable apolar structures and different polar head groups, NBD-hexadecylamine and RG-tetradecylamine (or -octadecylamine), were compared in lipid bilayers at a molar ratio of 1/50 at 23degreesC. Bilayers examined were in the solid, liquid-disordered, or liquid-ordered phases. While NBD-hexadecylamine was soluble in all the examined bilayer membrane phases, RG-tetradecylamine was stably soluble only in the liquid-disordered phase. RG-tetradecylamine insolubility in solid and liquid-ordered phases manifests itself as an aggregation of the amphiphile over a period of several days and the kinetics of aggregation were studied. Solubility of these amphiphiles in the different phases examined seems to be related to the dipole moment of the amphiphile (in particular, of the polar fluorophore) and its orientation relative to the dipolar potential of the membrane. We propose that amphiphilic molecules inserted into membranes (including lipid-attached proteins) partition into different coexisting membrane phases based upon: (1) nature of the apolar structure (chain length, degree of saturation, and chain branching as has been proposed in the literature); (2) magnitude and orientation of the dipole moment of the polar portion of the molecules relative to the membrane dipolar potential; and (3) hydration forces that are a consequence of ordering of water dipoles at the membrane surface. (C) 2002 Elsevier Science (USA). All rights reserved.
引用
收藏
页码:596 / 603
页数:8
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