CHEMISTRY AND BIOCHEMISTRY OF ENERGY TRANSFER

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The calcium-transporting ATPase will be examined with the following goals. (A) Determine the nature of the change in catalytic specificity toward phosphate compounds of two forms of the enzyme that normally react with ATP and phosphate, by examination of alternate substrates and phosphate acceptoprs. (B) Determine if potassium ion is occluded during one or more of the steps of the catalytic cycle. (C) Complete the thermodynamic cycle for the enzyme by measuring the equilibrium constant for binding of calcium to enzyme-phosphate. (D) Examine the nature of the slow dissociation of ATP from enzyme-calcium. Succinyl-CoA:acetoacetate coenzyme A transferase will be examined using portions of the coenzyme A molecule separately and together to characterize the rate acceleration of 10 to the 12 brought about by noncovalent interactions with coenzyme A. The strength of hydrogen bonds between small molecules in aqueous solution will be examined using a spectrophotometric technique, and dipole-diplole interactions in water will be characterized by measuring equilibrium constants for addition of substituted alcohols to substituted benzene derivatives. The reported change in mechanism from monomolecular to bimolecular for reactions of benzoyl chlorides will be examined with different nucleophiles to characterize the change in reaction mechanism. General acid catalysis of the addition of water and alcohols to acetaldehyde will be examined to determine if the mechanism involves concerted catalysis. Reactions of substituted methoxymethyl derivatives with nucleophiles will be examined in an attempt to cross the "borderline" between concerted and stepwise reaction mechanisms. The lifetimes of carbanion intermediates will be estimated using diffusion-controlled trapping reactions, and the lifetimes will be related to the mechanisms of elimination mechanisms. Structure-reactivity correlations will be carried out on reactions of substituted phosphates to determine if these reactions proceed through a concerted reaction mechanism rather than a metaphosphate intermediate.