Dissipative Dynamics of Enzymes

We explore enzyme conformational dynamics at sub - $\AA$ resolution, specifically temperature effects. The ensemble averaged mechanical response of the folded enzyme is viscoelastic in the whole temperature range between the warm and cold denaturation transitions. The dissipation parameter $\gamma$ of the viscoelastic description decreases by a factor 2 as the temperature is raised from 10 C to 45 C; the elastic parameter $K$ shows a similar decrease. Thus when probed dynamically, the enzyme softens for increasing temperature. Equilibrium mechanical experiments with the DNA spring (and a different enzyme) also show, qualitatively, a small softening for increasing temperature.