An important thrust of chemists and biochemists over the years has been to understand the nature of catalytic processes and use this knowledge to design improved catalysts. To attain these goals it is necessary to perform experiments that provide information regarding the nature of transition states and how catalysts influence them. A remarkable example of how this knowledge can be put to use is the recent development of catalytic antibodies based on the principle of transition state stabilization. It is the aim of the present investigation to add to an understanding of how metal ions influence transition states in group and proton transfer reactions. Over the years a large number of studies have appeared in the literature regarding the influence of metal ions on the rates of group and proton transfer processes in living and non-living systems. Out of these studies a number of chemically plausible reasons for the metal ion effects had been proposed, but the these explanations have suffered from being restricted to a qualitative nature. A recent breakthrough which leads to quantification is the discovery that rate changes induced by metal ions in a number of reactions conform to the Marcus equation. This property makes it possible to calculate reasonably accurate values of rate constants for use in situations where they are not experimentally accessible; or, in situations where rate constants can be determined, enables the extraction of valuable information regarding the chemical nature of the reaction pathway and its transition state. Valuable insight into several catalytic processes has already been obtained using the proposed methodology. The first reactions studied were relatively simple, but lately the principles have been successfully extended to more complicated systems that involve concerted reactions. It is the goal of this investigation to subject these procedures and the conclusions drawn from them to rigorous tests, and to determine to what extent the principles have general validity. It is proposed in this investigation to study metal ion effects in enolization, hydration, hemiketal dissociation and condensation reactions. The chemistry of the biologically important intermediate, enolpyruvate, is also to be investigated. Important in biological energy transport is phosphoryl transfer from triphosphates. Valuable insight into the nature of the transition state for phosphoryl transfer reactions from triphosphate has been gained in an earlier study and further investigations on these systems are to be performed.
NIH ExPorter
NIH ExPorter