Mitrakos P, Macdonald P M
Department of Chemistry and Erindale College, University of Toronto, Mississauga, Ontario, Canada.
Biochemistry. 1996 Dec 24;35(51):16714-22. doi: 10.1021/bi961911h.
2H NMR spectroscopy was used to investigate the response of specifically choline-deuterated 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) to changes in surface electrostatic charge in membranes consisting of mixtures of POPC plus various cationic amphiphiles plus polyadenylic acid (polyA). Three different cationic amphiphiles were investigated: cetyltrimethylammonium bromide (CTAB), dioleoyldimethylaminopropane (DODAP), and 3 beta [N-(N',N'-dimethylaminoethane)carbamoyl]-cholesterol (DC-CHOL). Each of the cationic amphiphiles elicited a concentration-dependent decrease (increase) in the quadrupolar splitting from POPC-alpha-d2 (POPC-beta-d2), as expected for the accumulation of cationic charges at the surface of a lipid bilayer. However, the strength of the response varied with the cationic amphiphile in the order CTAB > DODAP > DC-CHOL. When polyA was added to the cationic amphiphile-containing lipid bilayers, the 2H NMR spectrum consisted of two overlapping Pake patterns, indicating the presence of two lipid domains with different effective surface charges and only slow exchange of lipids between the two domains. There was no evidence of any non-bilayer lipid arrangements. Analysis of the quadrupolar splittings of the two 2H NMR spectral components demonstrated that the polyA-containing domain was enriched with respect to cationic amphiphiles while the polyA-free domain was depleted with respect to cationic amphiphiles. We conclude that polyA is able to laterally segregate cationic amphiphiles into long-lived lipid domains of distinct composition.
采用2H核磁共振光谱法研究了特定胆碱氘代的1-棕榈酰-2-油酰基-sn-甘油-3-磷酸胆碱（POPC）对由POPC与各种阳离子两亲物加聚腺苷酸（polyA）组成的膜表面静电荷变化的响应。研究了三种不同的阳离子两亲物：十六烷基三甲基溴化铵（CTAB）、二油酰基二甲基氨基丙烷（DODAP）和3β-[N-（N'，N'-二甲基氨基乙烷）氨基甲酰基]-胆固醇（DC-CHOL）。正如脂质双层表面阳离子电荷积累所预期的那样，每种阳离子两亲物都引起了POPC-α-d2（POPC-β-d2）四极分裂的浓度依赖性降低（增加）。然而，响应强度随阳离子两亲物的不同而变化，顺序为CTAB>DODAP>DC-CHOL。当将polyA添加到含阳离子两亲物的脂质双层中时，2H核磁共振光谱由两个重叠的帕克图案组成，表明存在两个具有不同有效表面电荷的脂质结构域，并且脂质在两个结构域之间仅缓慢交换。没有任何非双层脂质排列的证据。对两个2H核磁共振光谱成分的四极分裂分析表明，含polyA的结构域富含阳离子两亲物，而不含polyA的结构域则缺乏阳离子两亲物。我们得出结论，polyA能够将阳离子两亲物横向分离成长寿命的、组成不同的脂质结构域。
