X-ray diffraction study of lipid bilayer membranes interacting with amphiphilic helical peptides: diphytanoyl phosphatidylcholine with alamethicin at low concentrations.
X-ray diffraction study of lipid bilayer membranes interacting with amphiphilic helical peptides: diphytanoyl phosphatidylcholine with alamethicin at low concentrations.
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DOI：
10.1016/s0006-3495(95)80418-2
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发表时间：
1995-06
影响因子：
3.4
通讯作者：
Yili Wu;K. He;S. Ludtke;Huey W. Huang
中科院分区：
文献类型：
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作者：
Yili Wu;K. He;S. Ludtke;Huey W. Huang
多种两亲性螺旋肽在低浓度时可平行吸附于膜表面，高浓度时可垂直插入膜中。此外，这种转变与肽的细胞溶解活性有关。双phytanoyl磷脂酰胆碱- alametin混合物的x射线片层衍射显示了alametin浓度对双层结构的影响。特别是，随着肽浓度的增加，双层厚度随肽脂摩尔比的增加而减小，从1:150到1:47；后者接近插入临界浓度的阈值。从双分子层厚度的减小，可以计算出脂链的横截面扩张。对于所研究的所有肽浓度，每个吸附肽的链区域的面积扩张是恒定的280 +/- 20 A2，这大约是吸附的alamethicin的横截面积。这意味着肽被吸附在碳氢化合物区域的界面上，使脂质基团横向分离。有趣的是，由肽吸附引起的链紊乱倾向于扩散到一个大的区域，直径可达100 a。讨论了双层变形长程性质的理论基础。
A variety of amphiphilic helical peptides have been shown to exhibit a transition from adsorbing parallel to a membrane surface at low concentrations to inserting perpendicularly into the membrane at high concentrations. Furthermore, this transition has been correlated to the peptides' cytolytic activities. X-ray lamellar diffraction of diphytanoyl phosphatidylcholine-alamethicin mixtures revealed the changes of the bilayer structure with alamethicin concentration. In particular, the bilayer thickness decreases with increasing peptide concentration in proportion to the peptide-lipid molar ratio from as low as 1:150 to 1:47; the latter is near the threshold of the critical concentration for insertion. From the decreases of the bilayer thickness, one can calculate the cross sectional expansions of the lipid chains. For all of the peptide concentrations studied, the area expansion of the chain region for each adsorbed peptide is a constant 280 +/- 20 A2, which is approximately the cross sectional area of an adsorbed alamethicin. This implies that the peptide is adsorbed at the interface of the hydrocarbon region, separating the lipid headgroups laterally. Interestingly, the chain disorder caused by a peptide adsorption tends to spread over a large area, as much as 100 A in diameter. The theoretical basis of the long range nature of bilayer deformation is discussed.