Fukushima K, Muraoka Y, Inoue T, Shimozawa R
Department of Chemistry, Faculty of Science, Fukuoka University, Japan.
Biophys Chem. 1988 Jul 15;30(3):237-44. doi: 10.1016/0301-4622(88)85019-1.
The effect of negatively charged dilauroylphosphatidic acid (DLPA) vesicles on the conformation of poly(L-lysine) was investigated by circular dichroism measurements. DLPA vesicles induced a conformational change of poly(L-lysine) from the random coil to beta-structure in 5 mM Tes, pH 7.0. The fraction of induced beta-structure (F beta) was determined via a procedure of curve fitting of the observed spectra to the reference spectra. F beta increased linearly with the molar ratio, r, of DLPA to lysine residues up to r congruent to 0.7, and reached a saturation value of 1 at r greater than 1. Within the range 0.7 less than or equal to r less than or equal to 1, precipitation occurred. The effect of dilution of the negative charge on vesicle membranes was examined by mixing DLPA with dilauroylphosphatidylcholine (DLPC). Although the beta-structure of poly(L-lysine) was also induced by mixed vesicles, the saturation value of F beta decreased with decreasing DLPA content in mixed vesicles. The variation in saturation value of F beta with the composition of mixed vesicles was interpreted in terms of the change in average distance between DLPA head groups in mixed vesicles.
通过圆二色性测量研究了带负电荷的二月桂酰磷脂酸（DLPA）囊泡对聚（L-赖氨酸）构象的影响。在5 mM Tes，pH 7.0条件下，DLPA囊泡诱导聚（L-赖氨酸）从无规卷曲构象转变为β-结构。通过将观察到的光谱与参考光谱进行曲线拟合的程序来确定诱导的β-结构分数（Fβ）。Fβ随DLPA与赖氨酸残基的摩尔比r线性增加，直至r约等于0.7时达到饱和值，当r大于1时达到饱和值1。在0.7≤r≤1范围内，会发生沉淀。通过将DLPA与二月桂酰磷脂酰胆碱（DLPC）混合来研究稀释囊泡膜上负电荷的影响。尽管混合囊泡也能诱导聚（L-赖氨酸）的β-结构，但混合囊泡中Fβ的饱和值会随着DLPA含量的降低而降低。Fβ饱和值随混合囊泡组成的变化是根据混合囊泡中DLPA头部基团之间平均距离的变化来解释的。
