Mobility of Water, Urea and Trimethylamine-N-Oxide Molecules in the Vicinity of Globular Protein

Molecular mobility in the hydration shell of the SNase globular protein in an aqueous solution with cosolvents (urea and trimethylamine oxide) is studied using all-atom molecular dynamic simulations. Average displacements of the molecules initially located in the successive layers around the protein are calculated over the same short period of time to characterize the diffusion mobility of the molecules depending on the distance to the protein. It is shown that solvent molecules have lower mobility near the protein, and the mobility of more distant molecules increases irregularly and correlates with the positions of the distribution function maxima of these molecules around the protein. After the second maximum of these functions, the mobility reaches its bulky values both for water and the cosolvent.