Durand D, Field M J, Quilichini M, Smith J C
Laboratoire Léon Brillouin, Centre d'Etudes de Saclay, Gif-sur-Yvette, France.
Biopolymers. 1993 May;33(5):725-33. doi: 10.1002/bip.360330502.
Zwitterionic L-alanine forms crystals containing strong hydrogen-bonding and methylmethyl interactions. Well-defined low-frequency lattice vibrations exist in the crystals involving correlated intermolecular motions on the picosecond timescale. A characterization of these vibrations is expected to provide useful information on the nature of nonbonded interactions in peptides and proteins. We examine some of the vibrations using coherent inelastic neutron scattering and computer simulation techniques. The neutron scattering measurements are used to determine phonon dispersion relations for the acoustic and some low-frequency optic modes in the crystal. There is evidence for interaction between the two lowest frequency optical phonons and the longitudinal acoustic mode. The velocity of sound is anisotropic and can be correlated with the hydrogen-bonding arrangement in the crystal. Corresponding phonon dispersion relations are derived from normal mode analyses of the crystal using the program CHARMM. Although some calculated vibrational frequencies are somewhat too high, the form of the calculated dispersion relations are in good agreement with experiment.
两性离子L-丙氨酸形成含有强氢键和甲基-甲基相互作用的晶体。晶体中存在明确的低频晶格振动，涉及皮秒时间尺度上的相关分子间运动。对这些振动进行表征有望为肽和蛋白质中非键相互作用的性质提供有用信息。我们使用相干非弹性中子散射和计算机模拟技术研究了其中一些振动。中子散射测量用于确定晶体中声学和一些低频光学模式的声子色散关系。有证据表明两个最低频率的光学声子与纵向声学模式之间存在相互作用。声速是各向异性的，并且可以与晶体中的氢键排列相关联。使用CHARMM程序从晶体的简正模式分析中导出相应的声子色散关系。尽管一些计算出的振动频率有些过高，但计算出的色散关系的形式与实验结果吻合良好。
