Many marine animals have trimethylamine N-oxide (TMAO) and urea in their bodies to adjust the osmotic pressure. TMAO and urea show opposite effects in (de-)stabilizing proteins, but it is believed that TMAO and urea cancel their effects on the protein stabilization. However, it was unclear how the TMAO-urea interaction in aqueous solution is. Here, combined ab initio molecular dynamics simulations, polarization-resolved femtosecond infrared pump-probe spectroscopy, and nuclear magnetic resonance spectroscopy reveal that the hydrophobic interaction between TMAO and urea is favorable in comparison with the hydrogen-bonding interaction. The association of the hydrophobic methyl group of TMAO with urea is driven by the large mismatch between the strong TMAO-water hydrogen bond and the weak urea-water hydrogen bond. Our observations provide a rationale for the counteraction of osmotic pressure resulting from urea by TMAO.

Hydrophobic vs. hydrophilic interactions of TMAO and urea

2019 Fall National Meeting

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