Studies on Conformation Analysis of Functional Peptides in Lipid Double Layr by UV Resonance Raman Spetrometry

紫外共振拉曼光谱（193nm）可用于各种环境下多肽和蛋白质的结构分析，因为它能选择性地观察到这些化合物的酰胺带。本文研究了Boc-（Ala-Aib）_n-OMe（n = 2，4，8）功能肽的构象及其在双分子脂膜上的聚集。拉曼光谱测量通过使用Ar/F准分子激光器作为光源和多波检测方法进行。从由二肉豆蔻酰磷脂酰胆碱制成的脂质体中存在的肽观察到归属于酰胺I、II、III和2V的拉曼信号。Boc-（Ala-Aib）_8-OMe包埋在脂膜上的酰胺带与CD谱确定为α-螺旋结构的聚赖氨酸的酰胺带波数雅阁。因此，这表明该肽在脂膜中的十六聚体具有α-螺旋结构。此外，四聚体和八聚体的结构也得到了证实：四聚体为不规则结构，八聚体为3_结构。<10>一个明确的相关性被确认之间所观察到的酰胺带的波数和肽的二级结构。根据分子动力学计算的正态振动模式，推测肽聚集体的酰胺V带向高波数方向移动，这与高浓度Boc-（Ala-Aib）_8-OMe时观察到的结果一致。这表明分子内氢键的数目或构象的稳定性下降，因为相关肽的结构扭曲。

UV resonance Raman spectrometry using 193nm for excitation is useful for the elucidation of the structures of peptides and proteins in various enviroments, since that enables to observe the amide bands of these compounds selectively. The purpose of this work is the analysis of the conformation of functional peptides, Boc- (Ala-Aib) _n-OMe (n=2,4,8), and their aggregation in bimolecular lipid membrane. Raman spectrometric measurement was carried out by using an Ar/F excimer laser as a light source and a multiple wave detection method. Raman signals to be ascribed to amide I,II,III and 2V were observed from the peptide which existed in liposome made from dimyristoyl phosphatidylcholine. The wavenumbers of the amide bands oberved from Boc- (Ala-Aib) _8-OMe exising in the lipid membrane were in fair accord with those from poly (L-lysine) , whose structure was ascribed to alpha-helix based on its CD spectrum. Thus, it suggests the hexadecamer of that peptide in lipid membrane has the alpha-helix structure. In addition, the structures of the tetramer and the octamer were confirmed : an irregular structure for the tetramer and the 3_<10> structure for the octamer. An explicit correlation was confirmed between the observed wavenumbers of the amide bands and the secondary structure of peptides. A shift of the amide V band to higher wavenumber for a peptide aggregate was expected from the calculation of normal vibration mode based on molecular dynamics and that agreed with the results observed with higher concentration of Boc- (Ala-Aib) _8-OMe. It suggests the number of intramolecular hydrogen bond or the stbility of the conformation is decreased because of the distorted structure of the associated peptide.