Chen L X, Strauss H L, Snyder R G
Department of Chemistry, University of California, Berkeley 94720.
Biophys J. 1993 May;64(5):1533-41. doi: 10.1016/S0006-3495(93)81522-4.
Bands associated with delocalized vibrational modes were identified in the isotropic Raman spectra of a series of polyglycine oligomers in aqueous solution as zwitterions and as cations. The dependence of these bands on conformational disorder and chain length was determined. The observed dependence is closely mimicked in spectra calculated for a series of corresponding model polypeptides. The simulated spectra were calculated in a skeletal approximation for ensembles of conformationally disordered chains. As the chain length of the conformationally disordered polypeptides increases, the observed isotropic spectra rapidly approach the spectrum of the infinitely long disordered chain. Convergence is nearly complete at the tripeptide for both the zwitterion and the cation. The stimulated spectra behave in essentially the same way. Convergence to the spectrum of the infinitely long chain is much more rapid for the conformationally disordered polyglycines than for the ordered polyglycines because of the mode localization that results from disorder. In the low-frequency region the bands in the calculated spectra have frequencies that are systematically dependent on chain length. These bands are related to the longitudinal acoustic modes of the ordered chain.
在一系列聚甘氨酸低聚物的水溶液的各向同性拉曼光谱中，与离域振动模式相关的谱带被识别为两性离子和阳离子。确定了这些谱带对构象无序和链长的依赖性。在为一系列相应的模型多肽计算的光谱中，观察到的这种依赖性被紧密模拟。模拟光谱是在骨架近似下为构象无序链的集合计算的。随着构象无序多肽链长的增加，观察到的各向同性光谱迅速接近无限长无序链的光谱。对于两性离子和阳离子，在三肽处收敛几乎完成。受激光谱的行为基本相同。由于无序导致的模式局域化，构象无序的聚甘氨酸比有序的聚甘氨酸更快地收敛到无限长链的光谱。在低频区域，计算光谱中的谱带频率系统地依赖于链长。这些谱带与有序链的纵向声学模式有关。
