IDENTIFICATION OF PHOSPHATIDYLSERINE AND PHOSPHATIDYLCHOLINE IN CALCIUM-INDUCED PHASE SEPARATED DOMAINS
IDENTIFICATION OF PHOSPHATIDYLSERINE AND PHOSPHATIDYLCHOLINE IN CALCIUM-INDUCED PHASE SEPARATED DOMAINS
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DOI：
10.1021/bi00283a032
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发表时间：
1983-01-01
期刊：
影响因子：
2.9
通讯作者：
ISAC, T
中科院分区：
文献类型：
--
作者：
HUI, SW;BONI, LT;ISAC, T
用冷冻断裂电镜、差示扫描量热法、X射线衍射、微探针X射线分析和31 P核磁共振等方法研究了钙离子诱导的牛脑磷脂酰丝氨酸（PS）和二棕榈酰磷脂酰胆碱（DPPC）混合多层囊泡相分离的形态学变化。在~（31）P NMR和微探针研究中，用二棕榈酰硫代磷脂酰胆碱（DPPC）代替DPPC标记PC [磷脂酰胆碱]。高达25%的PS，有没有检测到的形态隔离诱导的20 mM Ca 2+。微探针分析表明，有横向分离的PC-和Ca-丰富的领域内相同的囊泡。通过~（31）P NMR观察到，Ca ~（2+）选择性地限制了P在PS中的运动。随着PS百分比的增加，层状重复间隔的增加也意味着DPPC富集结构域的形成。在30- 50%PS和超过20 mM Ca 2+之间，观察到小的卷状物从多层囊泡的表面滚出来。大多数样品呈小卷状和小泡状。X-射线衍射表明这两种类型的结构共存。Microphobe分析表明，钙和S优先与耳蜗和小泡，分别在样品中含有thionphosphatidylcholine。发生宏观结构变化的临界浓度为30%PS。PS螯合钙从多层囊泡形成PS富集的脂质卷，导致相应的富集DPPC在剩余的小囊泡。据推测，宏观形态偏析发生时，只有微观域扩展超过一个给定的临界尺寸。
Morphological changes associated with Ca-induced phase separation in mixed bovine brain phosphatidylserine (PS) and dipalmitoylphosphatidylcholine (DPPC) multilamellar vesicles were investigated by freeze-fracture EM, differential scanning calorimetry, X-ray diffraction, microprobe X-ray analysis and 31P NMR. Dipalmitoylthionphosphatidylcholine was substituted for DPPC to label PC [phosphatidylcholine] in 31P NMR and microprobe studies. Up to 25% of PS, there was no detectable morphological segregation induced by 20 mM Ca2+. Microprobe analysis showed that there were laterally separated PC- and Ca-rich domains within the same vesicles. The motion of P in PS, as observed by 31P NMR, was selectively restricted by Ca2+. The increasing lamellar repeat spacings with increasing PS percentage also implied the formation of DPPC-enriched domains. Between 30-50% PS and in excess of 20 mM Ca2+, small cochleates were observed to roll out of the surfaces of multilamellar vesicles. The majority of the samples were in the form of small cochleates and small vesicles. X-ray diffraction showed the coexistence of both types of structures. Microphobe analysis showed that Ca and S preferentially associated with cochleates and small vesicles, respectively, in samples containing thionphosphatidylcholine. The critical concentration at which macroscopic structural changes occurred was 30% PS. PS was sequestered by Ca from multilamellar vesicles to form PS-enriched cochleates, resulting in a corresponding enrichment of DPPC in the remaining small vesicles. Presumably, the macroscopic morphological segregation occurred only when the microscopic domains extended beyond a given critical size.