Influence of the amino-acid sequence on the inverse temperature transition of elastin-like polymers.

This work explores the dependence of the inverse temperature transition of elastin-like polymers (ELPs) on the amino-acid sequence, i.e., the amino-acid arrangement along the macromolecule and the resulting linear distribution of the physical properties (mainly polarity) derived from it. The hypothesis of this work is that, in addition to mean polarity and molecular mass, the given amino-acid sequence, or its equivalent--the way in which polarity is arranged along the molecule--is also relevant for determining the transition temperature and the latent heat of that transition. To test this hypothesis, a set of linear and di- and triblock ELP copolymers were designed and produced as recombinant proteins. The absolute sequence control provided by recombinant technologies allows the effect of the amino-acid arrangement to be isolated while keeping the molecular mass or mean polarity under strict control. The selected block copolymers were made of two different ELPs: one exhibiting temperature and pH responsiveness, and one exhibiting temperature responsiveness only. By changing the arrangement and length of the blocks while keeping other parameters, such as the molecular mass or mean polarity, constant, we were able to show that the sequence plays a key role in the smart behavior of ELPs.