Giraud Gerard, Karolin Jan, Wynne Klaas
Department of Physics, University of Strathclyde, Glasgow G4 0NG, Scotland, United Kingdom.
Biophys J. 2003 Sep;85(3):1903-13. doi: 10.1016/S0006-3495(03)74618-9.
The low-frequency (1-200 cm(-1)) vibrational spectra of peptides and proteins in solution have been investigated with ultrafast optical heterodyne-detected Raman-induced Kerr-effect spectroscopy (OHD-RIKES). Spectra have been obtained for di-L-alanine (ALA(2)) and the alpha-helical peptide poly-L-alanine (PLA) in dichloroacetic acid solution. The poly-L-alanine spectrum shows extra amplitude compared to the di-L-alanine spectrum, which can be explained by the secondary structure of the former. The globular proteins lysozyme, alpha-lactalbumin, pepsin, and beta-lactoglobulin in aqueous solution have been studied to determine the possible influence of secondary or tertiary structure on the low-frequency spectra. The spectra of the globular proteins have been analyzed in terms of three nondiffusive Brownian oscillators. The lowest frequency oscillator corresponds to the so-called Boson peak observed in inelastic neutron scattering (INS). The remaining two oscillators are not observed in inelastic neutron scattering, do therefore not involve significant motion of hydrogen atoms, and may be associated with delocalized backbone torsions.
利用超快光学外差检测拉曼诱导克尔效应光谱（OHD-RIKES）研究了溶液中肽和蛋白质的低频（1 - 200 cm⁻¹）振动光谱。已获得二聚L-丙氨酸（ALA₂）和α-螺旋肽聚L-丙氨酸（PLA）在二氯乙酸溶液中的光谱。与二聚L-丙氨酸光谱相比，聚L-丙氨酸光谱显示出额外的振幅，这可以由前者的二级结构来解释。对水溶液中的球状蛋白质溶菌酶、α-乳白蛋白、胃蛋白酶和β-乳球蛋白进行了研究，以确定二级或三级结构对低频光谱的可能影响。球状蛋白质的光谱已根据三个非扩散布朗振子进行了分析。最低频率的振子对应于在非弹性中子散射（INS）中观察到的所谓玻色子峰。其余两个振子在非弹性中子散射中未观察到，因此不涉及氢原子的显著运动，并且可能与离域的主链扭转有关。
