Understanding The Temperature Variation of Biological and other Catalysed Reactions

This is a fully funded 4-year PhD project associated the Centre for Doctoral Training in Theory and Modelling in the Chemical Sciences (TMCS), with year-one study in Oxford and a three-year research project at the University of Bristol.

Year-one training is delivered by academics from the Universities of Southampton, Bristol and Oxford, and covers fundamental theory, software development, and key application domains. Successful completion of year one will lead to the award of an Oxford MSc, and progression to the 3-year PhD research project, which will be based at the University of Bristol.

The aim of this project is to probe the effects of the temperature dependence of enthalpies and entropies on the rates of enzyme and other catalyzed reactions and processes in solid-state materials using a combination of simple models and simulation. It is often simply assumed that enthalpies and entropies of activation are temperature independent, and this assumption often works well for many reactions involving small molecules in common solvents. But increasingly it appears [1,2] that there is a more complex variation with temperature for enzyme-catalysed reactions linked to negative values of the heat capacity of activation between the reactants and the transition state We will examine the many possible factors that can give rise to such negative values in enzyme and non-enzyme catalysed reactions, examining in particular the number of thermally accessible low frequency vibrational modes and how these change as reaction proceeds. There are strong parallels in materials and inorganic chemistry to be explored – changes in the number of low frequency modes give rise to such apparently puzzling phenomena as negative thermal expansion over wide temperature ranges [3] and non-Arhennius variations in diffusion rates.

There are important implications for these results - in rationalising enzyme size and mass (why are enzymes so large?) and in the exciting prospect of designing new catalysts. And can we produce new improved heterogeneous inorganic catalysts?