Gramicidin A Aggregation in Supported Gel State Phosphatidylcholine Bilayers

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• 作者：Jianxun Mou ; Daniel M. Czajkowsky ; and Zhifeng Shao
• 刊名：Biochemistry
• 出版年：1996
• 出版时间：March 12, 1996
• 年：1996
• 卷：35
• 期：10
• 页码：3222 - 3226
• 全文大小：313K
• 年卷期：v.35,no.10(March 12, 1996)
• ISSN：1520-4995

文摘

Using an atomic force microscope, supported bilayers of saturatedphosphatidylcholine (inthe gel state) containing various amounts of gramicidin A (gA) wereimaged in aqueous solutions and atroom temperature. gA clusters were directly observed for the firsttime under these conditions. It wasfound that, at a lower gA concentration, gA aggregated into domains,composed of small clusters alongwith a considerable amount of lipids. This basic aggregation unit,most likely a hexamer, remained thesame for acyl chain lengths from 14 to 18 carbons. These smallclusters were observed to form elongatedaggregates (line type) but never into extended pure gA domains.When gA concentrations were increased,for bilayers with 16 carbons or less, gA aggregated into larger domainsbut the basic unit remained separatedby lipid molecules. At about 5 mol % gA, a percolation-liketransition occurred at which the line typeaggregates were connected to each other. However, for bilayerswith more than 16 carbons, multiplelamellar strucutres were formed at higher gA fractions and the toplayer had a ripple-like surfacemorphology. The molecular mechanism for the formation of thesepeculiar structures remains to beelucidated.