A Rationalization of the Effect That TMAO, Glycine, and Betaine Exert on the Collapse of Elastin-like Polypeptides

Elastin-like polypeptides (ELPs) are soluble in water at low temperature, but, on increasing the temperature, they undergo a reversible and cooperative, coil-to-globule collapse transition. It has been shown that the addition to water of either trimethylamine N-oxide (TMAO), glycine, or betaine causes a significant decrease of T(collapse) in the case of a specific ELP. Traditional rationalizations of these phenomena do not work in the present case. We show that an alternative approach, grounded in the magnitude of the solvent-excluded volume effect and its temperature dependence (strictly linked to the translational entropy of solvent and co-solute molecules), is able to rationalize the occurrence of ELP collapse in water on raising the temperature, as well as the T(collapse) lowering caused by the addition to water of either TMAO, glycine, or betaine.

Automated summary

Elastin-like polypeptides (ELPs) are soluble in water at low temperature but undergo a reversible coil-to-globule collapse transition upon increasing the temperature. The addition of trimethylamine N-oxide (TMAO), glycine, or betaine to water causes a significant decrease in the collapse temperature (T(collapse)) of a specific ELP. An alternative approach based on the solvent-excluded volume effect and its temperature dependence is able to explain the ELP collapse and the lowering of T(collapse) induced by the addition of TMAO, glycine, or betaine.