Solvent mobility and the protein 'glass' transition

Proteins and other biomolecules undergo a dynamic transition near 200 K to a glass-like solid state with small atomic fluctuations. This dynamic trans ition can inhibit biological function. To provide a deeper understanding of the relative importance of solvent mobility and the intrinsic protein ener gy surface in the transition, a novel molecular dynamics simulation procedu re with the protein and solvent at different temperatures has been used. So lvent mobility is shown to be the dominant factor in determining the atomic fluctuations above 180 K, although intrinsic protein effects become import ant at lower temperatures. The simulations thus complement experimental stu dies by demonstrating the essential role of solvent in controlling function ally important protein fluctuations.