Pokorny A, Almeida P F, Melo E C, Vaz W L
Universidade de Coimbra, Departamento de Química, 3049 Coimbra Codex, Portugal.
Biophys J. 2000 Jan;78(1):267-80. doi: 10.1016/S0006-3495(00)76590-8.
We examined the consequences of membrane heterogeneity for the association of a simple amphiphilic molecule with phospholipid vesicles with solid-liquid and liquid-liquid phase coexistence. To address this problem we studied the association of a single-chain, fluorescent amphiphile with dimyristoylphosphatidylcholine (DMPC) vesicles containing varying amounts of cholesterol. DMPC bilayers containing 15 mol% cholesterol show a region of solid-liquid-ordered (s-l(o)) coexistence below the T(m) of pure DMPC (23.9 degrees C) and a region of liquid-disordered-liquid-ordered coexistence (l(d)-l(o)) above the T(m). We first examined equilibrium binding and kinetics of amphiphile insertion into single-phase vesicles (s, l(d), and l(o) phase). The data obtained were then used to predict the behavior of the equivalent process in a two-phase system, taking into account the fractions of phases present. Next, the predicted kinetics were compared to experimental kinetics obtained from a two-phase system. We found that association of the amphiphile with lipid vesicles is not influenced by the existence of l(d)-l(o) phase boundaries but occurs much more slowly in the s-l(o) phase coexistence region than expected on the basis of phase composition.
我们研究了膜的非均质性对于一种简单两亲分子与具有固-液相和液-液相共存的磷脂囊泡缔合的影响。为了解决这个问题，我们研究了一种单链荧光两亲物与含有不同量胆固醇的二肉豆蔻酰磷脂酰胆碱（DMPC）囊泡的缔合。含有15摩尔%胆固醇的DMPC双层在纯DMPC的熔点（23.9℃）以下显示出一个固-液有序（s-l(o)）共存区域，在熔点以上显示出一个液-无序-液-有序共存区域（l(d)-l(o)）。我们首先研究了两亲物插入单相囊泡（s、l(d)和l(o)相）的平衡结合和动力学。然后，考虑到存在的相的比例，将获得的数据用于预测两相系统中等效过程的行为。接下来，将预测的动力学与从两相系统获得的实验动力学进行比较。我们发现，两亲物与脂质囊泡的缔合不受l(d)-l(o)相界存在的影响，但在s-l(o)相共存区域中发生的速度比基于相组成预期的要慢得多。
