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Rate constants and activation parameters for the mobility of bulk and DNA‐associated glycol–water solvents
Author(s) -
Milton John G.,
Galley William C.
Publication year - 1986
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.360250911
Subject(s) - chemistry , arrhenius equation , reaction rate constant , solvent , entropy of activation , dna , atmospheric temperature range , melting temperature , solvent effects , thermodynamics , activation energy , chemical physics , kinetics , organic chemistry , biochemistry , physics , materials science , quantum mechanics , composite material
Abstract The decrease in mobility of viscous glycol–water solvents when associated with native DNA is quantified from a study of the loss of the exciting‐wavelength dependence of the phosphorescence spectrum of free and bound proflavin with increasing temperature. The data are interpreted in terms of a distribution of rate constants with an Arrhenius temperature dependence. Over the temperature range of the experiments a relative decrease of ∼ 10 4 in the average rate constant is observed for reorientation of the solvent when associated with DNA. The basis for this large reduction is found to derive from a large decrease in the pre‐exponential factors (i.e., activation entropy) associated with the reorientation rate constants. The changes in the distribution of rate constants and the activation parameters for solvent mobility induced by DNA do not resemble the changes observed for any one of a number of small ion or molecule perturbations. The results suggest the presence of disorganized, relatively immobile solvent in association with DNA.