ISSN:
0006-3525
Keywords:
Chemistry
;
Polymer and Materials Science
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
Notes:
The temperature dependence of hydrogen isotope exchange rates for lysozyme in 5 molal aqueous glycerol and for poly (D,L-alanine) in a range of glycerol concentrations from 0 molal to 8 molal have been determined. The activation enthalpy of base-catalyzed exchange for poly (D,L-alanine) in water is 4 kcal/mol and passes through a minimum at about 2 molal glycerol before returning to a value of 4 kcal/mol at 4 molal glycerol. Exchange rates for lysozyme have been analyzed with transition state and Kramers's theories. The activation parameters for exchange of protons in lysozyme in the presence of 5 molal glycerol show a similar qualitative behavior to those determined for exchange in the absence of glycerol [R. B. Gregory et al. (1982) Biochemistry 24, 6523-6530]. The activation enthalpies and entropies for the fast-exchanging protons show a gentle increase as H(t), the number of hydrogens remaining unexchanged, decreases. By contrast, the activation parameters for the slowest exchanging protons [H(t) 〈 20] increase dramatically as H(t) decreases. As in water, the activation parameters for exchange of the fast- and slow-exchanging protons in glycerol solution are characterized by two distinct compensation temperatures (510 ± 100 K for the fast protons and 340 ± 40K for the slow protons). These values are not significantly different from those determined for exchange in water.The activation parameters, ΔH
Additional Material:
7 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/bip.360290808
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