Thermodynamic, motional, and structural aspects of gramicidin-induced hexagonal HII phase formation in phosphatidylethanolamine.
Thermodynamic, motional, and structural aspects of gramicidin-induced hexagonal HII phase formation in phosphatidylethanolamine.
复制标题
磷脂酰乙醇胺中短杆菌肽诱导的六方 HII 相形成的热力学、运动和结构方面。
DOI：
10.1021/bi00348a006
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发表时间：
1985
期刊：
影响因子：
2.9
通讯作者：
B. de Kruijff
中科院分区：
文献类型：
--
作者：
J. Killian;B. de Kruijff
用差示扫描量热法研究了葛兰素对磷脂酰胆碱(PC)和磷脂酰乙醇胺(PE)分散体热力学性质的影响。结果表明，在PC体系中引入甘草酸，降低了凝胶向液晶相转变的能量含量。然而，当加入到PE体系中时，该肽不影响凝胶向液晶相转变的性质，只是在较高浓度下，熔融过程的起始温度被移动到略低的温度。因此，我们假设在PE的片状凝胶状态下，多肽发生聚集。为了更深入地了解甘草素-PE相互作用的本质，我们利用31P和13C核磁共振和小角X射线衍射法研究了甘草苷/PE体系中HⅡ相形成的运动和结构细节。与早期的结果一致[Van Echteld，C.J.，Van Stigt，R.，de Kruijff，B.，Leunissen-Bijvelt，J.，Verkleij，A.J.，&de Gier，J.(1981)Biochim。生物群落。结果表明，在PE体系中，Granicidin的掺入降低和加宽了双分子层到六方相变。~(31)P核磁共振化学位移各向异性(CSA)测量表明，在贫Granicidin的片状相和富Granicidin的HII相之间存在相分离。CSA和自旋-晶格驰豫时间(T1)的联合测量表明，在HII相中，Granicidin降低了PE中磷酸盐部分的分子有序性，增加了其运动速度。另外，~(13)C核磁共振线宽测量表明，在HII相中的酰基链比在片状相中的无序程度更高，并且在纯PE的HII相中也出现了与富含甘草素的HII相类似的无序。这一解释得到了X射线衍射数据的支持，该数据显示两种类型的HII相的一级重复距离相似。饱和转移核磁共振实验表明，在1-2 S的时间尺度内，片层相和HⅡ相之间没有发生交换，表明存在宏观相分离。最后，我们讨论了甘草苷与脂类的相互作用，特别是甘草苷在PE和PC体系中的HII相的形成。结果表明，多肽的聚集在HII相的形成中起着关键作用。
The effect of gramicidin incorporation on the thermodynamic properties of phosphatidylcholine (PC) and phosphatidylethanolamine (PE) dispersions was investigated by differential scanning calorimetry. The results show that incorporation of gramicidin in PC systems results in a decrease of the energy content of the gel to liquid-crystalline phase transition. When incorporated in PE systems, however, the peptide does not affect the properties of the gel to liquid-crystalline phase transition with the exception that at high gramicidin concentrations the onset of the melting process is shifted to a slightly lower temperature. We therefore assume that in the lamellar gel state of PE aggregation of the peptide occurs. To get more insight into the nature of the gramicidin-PE interaction, we studied the motional and structural details of HII phase formation in gramicidin/PE systems with the use of 31P and 13C nuclear magnetic resonance (NMR) and small-angle X-ray diffraction. In agreement with earlier results [Van Echteld, C. J. A., Van Stigt, R., de Kruijff, B., Leunissen-Bijvelt, J., Verkleij, A. J., & De Gier, J. (1981) Biochim. Biophys. Acta 648, 287-291] it was shown that gramicidin incorporation lowers and broadens the bilayer to hexagonal HII phase transition in PE systems. 31P NMR chemical shift anisotropy (CSA) measurements indicated that a phase separation occurs between a gramicidin-poor lamellar phase and a gramicidin-rich HII phase. From combined CSA and spin-lattice relaxation time (T1) measurements it was suggested that in the HII phase gramicidin decreases the molecular order and increases the rate of motion of the phosphate moiety of PE. In addition, 13C NMR line width measurements indicated that the acyl chains are more disordered in the HII phase than in the lamellar phase and that a similar disorder occurs in the HII phase of the pure PE as in the gramicidin-rich HII phase. This interpretation was supported by the X-ray diffraction data, which show similar first-order repeat distances in both types of HII phase. From saturation-transfer NMR experiments in PE and gramicidin-PE mixtures it was shown that no exchange occurs between the lamellar and the HII phases in the time scale of 1-2 s, suggesting a macroscopic phase separation. Finally, we discussed the gramicidin-lipid interaction and in particular the HII phase formation by gramicidin in PE and in PC systems. It is proposed that aggregation of the peptide plays a crucial role in HII phase formation.