Trimethylamine-N-oxide (TMAO) stabilizes and urea de-stabilizes proteins in aqueous solution, and the two effects are counteracted at a 1:2 ratio of TMAO to urea. In addition, some marine animals use a mixture of TMAO and urea as osmolytes. Since the ratio of TMAO increases with depth of the organism, TMAO also appears to be a "piezolyt'' that protects against high pressure. Our molecular dynamics simulations of TMAO, urea, and TMAO-urea in aqueous solution at different concentrations and different hydrostatic pressures point to a reason for these effects. For aqueous solutions of urea, the diffusion of water in the solution increases as pressure increases. Interestingly, for aqueous solutions of TMAO and urea at ratios found in marine animals who live at depths corresponding to the simulation pressure, the diffusion of water is almost constant as pressure increases. At a molecular level, the differences in the hydrogen bonding interactions between the solutes and water appear responsible for this effect. Moreover, the rate of water diffusion further affects the hydrogen bonding interactions with other solutes (and presumably interfaces), thus providing an explanation for the protective effects.<br/>

Aqueous solutions of TMAO and urea under pressure: Molecular dynamics simulation study

2019 Fall National Meeting

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