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Solvent effects on the dynamics of (dG‐dC) 3
Author(s) -
Freier Susan M.,
Albergo Diane Deprisco,
Turner Douglas H.
Publication year - 1983
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.360220408
Subject(s) - chemistry , dissociation (chemistry) , oligomer , solvent , kinetics , urea , glycerol , helix (gastropod) , ethanol , crystallography , analytical chemistry (journal) , chromatography , organic chemistry , ecology , physics , quantum mechanics , snail , biology
The kinetics of the coil‐to‐helix transition of (dG‐dC) 3 in M NaCl, 45 m M sodium cacodylate, pH 7, were measured in H 2 O, D 2 O, 10 mol % ethanol, 10 mol % urea, and 10 mol % glycerol. At 43°C in H 2 O the recombination rate is 1.3 ± 0.2 × 10 7 M −1 s −1 ; the dissociation rate is 68 ± 10 s −1 . The destabilization of the helix in 10 mol % ethanol and 10 mol % urea relative to water is primarily due to a large increase in the helix‐dissociation rate. In 10 mol % glycerol, the destabilization of the helix is due to a decrease in the recombination rate and an increase in the dissociation rate. Above 20°C, two exponential decays longer than 1 μs are observed after a temperature jump. The slower relaxation time is 4–10 times faster than the bimolecular component and is independent of oligomer concentration. We attribute this relaxation to a rapid equilibrium between two helical states. At low temperatures and oligomer concentrations of 1 m M or greater, the helices aggregate in 1 M NaCl. Experimental data are presented under conditions where aggregation is unimportant and evidence is given that the Δ H ‐determined spectroscopically is unaffected by aggregation.