MONOLAYER CHARACTERISTICS AND THERMAL-BEHAVIOR OF NATURAL AND SYNTHETIC PHOSPHATIDYLSERINES
MONOLAYER CHARACTERISTICS AND THERMAL-BEHAVIOR OF NATURAL AND SYNTHETIC PHOSPHATIDYLSERINES
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DOI：
10.1021/bi00400a025
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发表时间：
1987-12-29
期刊：
影响因子：
2.9
通讯作者：
HAUSER, H
中科院分区：
文献类型：
--
作者：
DEMEL, RA;PALTAUF, F;HAUSER, H
介绍了不同磷脂酰丝氨酸的单分子膜性质和热行为。在中性pH和22 ℃下，C，饱和磷脂酰丝氨酸形成凝聚单层，而不饱和磷脂酰丝氨酸形成液体膨胀膜。在类似条件下，二肉豆蔻酰磷脂酰丝氨酸经历从液体膨胀到凝聚状态的转变。在pH 4和22 ℃下，C，表面压力-面积等温线转移到较小的面积相对于在中性pH值记录的单层。在pH值4观察到的冷凝是接近在pH值7.4通过添加10 mM氯化钙。就单层中的分子堆积和热行为而言，1，2-二棕榈酰-SN-甘油-3-磷酸-L-丝氨酸（DPPS）及其醚类似物相似，但不完全相同。低于30 mN/m时，醚类似物的单层甚至比DPPS的单层更致密。醚类似物的有序-无序转变通常发生在比二酰基化合物更高的温度下。超声处理的磷脂酰丝氨酸分散液组成的小单层囊泡显示异常的热性能相比，超声处理的磷脂酰胆碱分散液。他们表现出尖锐的有序无序转变，在类似的温度，甚至略有升高相比，未经超声处理的磷脂酰丝氨酸分散体。这种异常现象可以用磷脂酰丝氨酸小囊泡双层膜的pH梯度来解释。内表面的pH比外表面的pH更酸性，导致磷脂酰丝氨酸分子的质子化。这又导致磷脂酰丝氨酸分子在内双层表面上的缩合。这种梯度被认为是高度弯曲的带负电荷的双层囊泡的热力学稳定性的原因。
The monolayer properties and thermal behavior of different phosphatidylserines are presented. At neutral pH and 22.degree. C, saturated phosphatidylserines form condensed monolayers while unsaturated phosphatidylserines form liquid-expanded films. Under similar conditions, dimyristoylphosphatidylserine undergoes a transition from the liquid-expanded to the condensed state. At pH 4 and 22.degree. C, the surface pressure-area isotherms are shifted to smaller areas relative to the monolayers recorded at neutral pH. The condensation observed at pH 4 is close to that produced at pH 7.4 by the addition of 10 mM CaCl2. As regards the molecular packing in monolayers and the thermal behavior, 1,2-dipalmitoyl-sn-glycero-3-phospho-L-serine (DPPS) and its ether analogue are similar, albeit not identical. Below 30 mN/m, monolayers of the ether analogue are even more condensed than those of DPPS. The order-disorder transition of the ether analogue occurs usually at higher temperatures than that of the diacyl compound. Sonicated phosphatidylserine dispersions consisting of small unilamellar vesicles show anomalous thermal properties compared to sonicated phosphatidylcholine dispersions. They exhibit sharp order-disorder transitions at similar or even slightly elevated temperatures compared to unsonicated phosphatidylserine dispersions. This anomaly is explained in terms of a pH gradient across the bilayer membrane of the small unilamellar phosphatidylserine vesicles The internal surface pH is more acidic than the external pH, leading to some protonation of phosphatidylserine molecules. This in turn leads to a condensation of phosphatidylserine molecules on the inner bilayer surface. Such a gradient is proposed to be responsible for the thermodynamic stability of highly curved negatively charged bilayer vesicles.