ISSN:
0006-3525
Keywords:
Chemistry
;
Polymer and Materials Science
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
Notes:
The kinetics of the coil-to-helix transition of (dG-dC)3 in M NaCl, 45 mM sodium cacodylate, pH 7, were measured in H2O, D2O, 10 mol % ethanol, 10 mol % urea, and 10 mol % glycerol. At 43°C in H2O the recombination rate is 1.3 ± 0.2 × 107 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 mM or greater, the helices aggregate in 1M NaCl. Experimental data are presented under conditions where aggregation is unimportant and evidence is given that the ΔH-determined spectroscopically is unaffected by aggregation.
Additional Material:
12 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/bip.360220408
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