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

Andrea Pica,Giuseppe Graziano

doi:10.3390/life12020140

Abstract

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.

Highlights

It is well-established that elastin-like polypeptides, Elastin-like polypeptides (ELPs), are soluble in water at low temperature and undergo a temperature-induced, reversible, and cooperative collapse transition, passing from extended, coil conformations to compact, globular ones [1,2,3]
The addition to water of either trimethylamine N-oxide (TMAO), glycine, or betaine stabilizes the globule state of ELP. This result can be considered as “expected” because all three co-solutes are stabilizing agents of the native state of globular proteins [5,6], and the globule state of ELP should resemble the native state of globular proteins
These results demonstrate unequivocally that there is no correlation between the T(collapse) lowering of ELP, common to all the three co-solutes, and their effect on: (1) the surface tension of the solutions; (2) the accumulation at the ELP surface; and (3) the position of the OH stretching band

Summary

Introduction

It is well-established that elastin-like polypeptides, ELPs, are soluble in water at low temperature and undergo a temperature-induced, reversible, and cooperative collapse transition, passing from extended, coil conformations to compact, globular ones [1,2,3]. We would like to apply the same theoretical approach to the collapse transition of ELP to try to provide a coherent rationalization of the effect the addition of either TMAO, glycine, or betaine has on T(collapse).

Results

Conclusion