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Intermolecular Overhauser effects in fluoroalcohol solutions of cyclo ‐alanylglycine
Author(s) -
Strickler M. A.,
Gerig J. T.
Publication year - 2002
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.10176
Subject(s) - intermolecular force , chemistry , solvent , nuclear overhauser effect , solvent effects , diffusion , computational chemistry , intermolecular interaction , thermodynamics , molecule , organic chemistry , physics
Abstract Interactions between the diketopiperazine cyclo ‐alanylglycine and four fluorinated alcohols in water–fluoroalcohol mixtures were examined by 1 H{ 19 F} intermolecular nuclear Overhauser effects (NOE) experiments. The alcohols studied were trifluoroethanol, hexafluoroacetone trihydrate, 1,1,1,3,3,3‐hexafluoroisopropanol and perfluoro‐ t ‐butanol. The experimental methods used permit detection of solvent–solute NOEs of 0.1% or less. Solute and solvent diffusion coefficients were determined and apparent molecular radii of the fluoroalcohols estimated. Using these data, it was shown that observed 1 H{ 19 F} intermolecular NOEs are consistent with expectations based on theory. A method for extending conventional theory to take into account the shape of a solute and the exposure of its hydrogens to solvent is described. This approach gives reasonable agreement with experimental results, particularly if it is assumed that solute–solvent interactions take place in such a way that the fluorines of a fluoroalcohol are preferentially oriented toward the solute during solute–solvent encounters. The results support the suggestion that intermolecular 1 H{ 19 F} NOEs may become a useful tool for studies of peptide and protein conformations in fluoroalcohol–water solvent mixtures. © 2002 Wiley Periodicals, Inc. Biopolymers 64: 227–235, 2002