We conducted molecular dynamics simulations of the process of unfolding of hen egg white lysozyme at high temperature in water and its mixtures with dimethyl sulfoxide (DMSO) containing 5 to 100 mole percent of DMSO. For each composition of the mixture, we recorded 30 ns long trajectories, for pure water - 130 ns long trajectories. During this time, lysozyme in water substantially loses its secondary structure and tertiary contacts, but stays in a compact globular state. In mixtures of water with DMSO, the globule is being lost during the simulation, and both secondary and tertiary structure are disrupted much faster than in pure water. Average times of unfolding of the tertiary structure determined using different criteria of formation of the unfolded state are in good agreement with each other. They decrease with increasing concentrations of DMSO up to 30 mole percent, and with a further increase remain at a constant level.
lysozyme, denaturation, molecular dynamics, kinetics
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