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Hydration dependence of backbone and side chain polylysine dynamics: A 13 C solid‐state NMR and IR spectroscopy study
Author(s) -
Krushelnitsky Alexey,
Faizullin Dzhigangir,
Reichert Detlef
Publication year - 2004
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.10540
Subject(s) - chemistry , side chain , molecular dynamics , nuclear magnetic resonance spectroscopy , polylysine , relaxation (psychology) , spectroscopy , resonance (particle physics) , two dimensional nuclear magnetic resonance spectroscopy , nuclear magnetic resonance , crystallography , analytical chemistry (journal) , chemical physics , computational chemistry , stereochemistry , organic chemistry , polymer , psychology , social psychology , physics , particle physics , quantum mechanics
The molecular dynamics of solid poly‐ L ‐lysine has been studied by the following natural abundance 13 C‐NMR relaxation methods: measurements of the relaxation times T 1 at two resonance frequencies, off‐resonance T 1ρ at two spin‐lock frequencies, and proton‐decoupled T 1ρ . Experiments were performed at different temperatures and hydration levels (up to 17% H 2 O by weight). The natural abundance 13 C‐CPMAS spectrum of polylysine provides spectral resolution of all types of backbone and side chain carbons and thus, dynamic parameters could be determined separately for each of them. At the same time, the conformational properties of polylysine were investigated by Fourier transform infrared spectroscopy. The data obtained from the different NMR experiments were simultaneously analyzed using the correlation function formalism and model‐free approach. The results indicate that in dry polylysine both backbone and side chains take part in two low amplitude motions with correlation times of the order of 10 −4 s and 10 −9 s. Upon hydration, the dynamic parameters of the backbone remain almost constant except for the amplitude of the slower process that increases moderately. The side chain dynamics reveals a much stronger hydration response: the amplitudes of both slow and fast motions increase significantly and the correlation time of the slow motion shortens by about five orders of magnitude, and at hydration levels of more than 10% H 2 O fast and slow side chain motions are experimentally indistinguishable. These changes in the molecular dynamics cannot be ascribed to any hydration‐dependent conformational transitions of polylysine because IR spectra reveal almost no hydration dependence in either backbone or side chain absorption domains. The physical nature of the fast and slow motions, their correlation time distributions, and hydration dependence of microdynamic parameters are discussed. © 2003 Wiley Periodicals, Inc. Biopolymers 73: 1–15, 2004