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Free Energy Changes in Denaturation of Ribonuclease A by Mixed Denaturants. Effects of Combinations of Guanidine Hydrochloride and One of the Denaturants Lithium Bromide, Lithium Chloride, and Sodium Bromide

Free Energy Changes in Denaturation of Ribonuclease A by Mixed Denaturants. Effects of Combinations of Guanidine Hydrochloride and One of the Denaturants Lithium Bromide, Lithium Chloride, and Sodium Bromide

F Ahmad

J Biol Chem. 1984 Apr 10;259(7):4183-6.

PMID: 6323462

Abstract:

The denaturation of ribonuclease A by guanidine hydrochloride, lithium bromide, and lithium chloride and by mixed denaturants consisting of guanidine hydrochloride and one of the denaturants lithium chloride, lithium bromide, and sodium bromide was followed by difference spectral measurements at pH 4.8 and 25 degrees C. Both components of mixed denaturant systems enhance each other's effect in unfolding the protein. The effect of lithium bromide on the midpoint of guanidine hydrochloride denaturation transition is approximately the sum of the effects of the constituent ions. For all the mixed denaturants tested, the dependence of the free energy change on denaturation is linear. The conformational free energy associated with the guanidine hydrochloride denaturation transition in water is 7.5 +/- 0.1 kcal mol-1, and it is unchanged in the presence of low concentrations of lithium bromide, lithium chloride, and sodium bromide which by themselves are not concentrated enough to unfold the protein. The conformational free energy associated with the lithium bromide denaturation transition in water is 11.7 +/- 0.3 kcal mol-1, and it is not affected by the presence of low concentrations of guanidine hydrochloride which by themselves do not disrupt the structure of native ribonuclease A.

Chemicals Related in the Paper:

Catalog Number	Product Name	Structure	CAS Number	Price
AP7550358	Lithium bromide		7550-35-8	Price

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