William P. Jencks - US grants

Uncoupling of the calcium transporting ATPase of sarcoplasmic reticulum by removal of the catalytic metal ion will be characterized further. The metal ion specificity and rate and equilibrium constants for development and disappearance of the uncoupling will be determined. The steps involving the binding and release of calcuim at the low affinity site will be measured directly to determine the mechanism and thermodynamics of these steps. Structure- reactivity correlations for nucleophilic reagents with phosphorylated pyridines will be done in order to determine if there is a metaphosphate intermediate in catalysis. Although an enormous amount of work has been carried out on chemical reactions that generate carbocations a limited amount of work has probed these indirectly by trapping reactions. This will be done. The substitution reactions at carbon will be investigated as will the ionization of thiamine. A mechanistic understanding of vectorial processes in biology is being established with this work. Knowledge of the basis the efficiency of catalytic processes in living systems is of great importance for fundamental work and for applications. The most rational approach to genetic engineering requires information at the level of mechanistic detail that this work provides

Mechanisms of group transfer reactions and their catalysis will be studied in enzymic and nonenzymic systems and mechanisms for the conversion of chemical energy into work will be examined with the calcium-transporting ATPase of sarcoplasmic reticulum. This subject is important in the control and function of healthy and diseased muscle. The role of exact fixation and entropy loss in enzyme catalysis will be probed with partial and complete substrates for Coenzyme A transferase and by examining small changes in the size of substituents that are remote from the reacting groups of substrates. Rate and equilibrium constants for formation and breaking of hydrogen bonds in aqueous solution will be examined. The mechanism of calcium internalization and the internal calcium binding site of the calcium ATPase will be characterized. Phosphoryl transfer will be examined by a search for general base catalysis and for catalysis of the cleavage of phosphorylated pyridines by alkaline phosphatase. Acyl cyanides will be examined as substrates for chymotrypsin in an attempt to estimate the role of proton transfer to the leaving group in catalysis; concerted proton transfer to the leaving cyanide is not possible. The mechanism of proton transfer between electronegative atoms will be examined by determining Bronsted plots and isotope effects for general acid and general base catalysis of ester aminolysis involving diffusion-controlled proton transfer. Reactions of acyl halides will be examined to evaluate the importance of acylium ion intermediates and the possibility of a bimolecular substitution mechanism. The mechanism of proton removal from carbon will be studied using the sulfonium ion as activating group to determine if there are changes in transition state structure with changing reactant structure; these compounds are expected to have a small intrinsic barrier for proton transfer that may make such changes more readily detectible.

This award provides funds that will aid in the acquisition of computer equipment and software by an outstanding group of biochemists and organic chemists at Brandeis University. The instrumentation will be used to aid in the research training of graduate students working in the emerging area of bioorganic chemistry. Increasingly, organic chemists and biochemists have come to realize that their disciplines have much to learn from and offer to each other. At Brandeis, such cross fertilization occurs in the context of research programs in areas as diverse as the study of enzyme mechanisms, synthesis of natural products and pharmaceuticals, molecular recognition, and the role of solvent molecules in chemical reactions. Work in these areas depends heavily of the use of computers for analysis and interpretation of experimental data, and, as well, the formulation of new lines of inquiry. The equipment acquired through this award will insure that the training of a new generation of investigators will proceed in an environment with adequate state of the art computational facilities.