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Lattice vibrations in crystalline L ‐alanine
Author(s) -
Durand Dominique,
Field Martin J.,
Quilichini Marguerite,
Smith Jeremy C.
Publication year - 1993
Publication title -
biopolymers
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.556
H-Index - 125
eISSN - 1097-0282
pISSN - 0006-3525
DOI - 10.1002/bip.360330502
Subject(s) - chemistry , phonon , anisotropy , inelastic neutron scattering , picosecond , dispersion relation , intermolecular force , normal mode , acoustic dispersion , molecular physics , hydrogen bond , crystal structure , molecular vibration , vibration , lattice (music) , dispersion (optics) , crystal (programming language) , neutron scattering , crystallography , scattering , condensed matter physics , optics , laser , physics , molecule , quantum mechanics , programming language , organic chemistry , computer science , acoustics
Abstract Zwitterionic L ‐alanine forms crystals containing strong hydrogen‐bonding and methyl‐methyl 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. © 1993 John Wiley & Sons, Inc.