School of Physics Soft Condensed Matter & Biophysics Seminar:  Prof. Luis Olivares-Quiroz, Autonomous University of Mexico City

Proteins are long heteropolymer chains composed of units called amino acids synthesized inside the cell by DNA translation and transcription in combination with the action of the ribosome and t-RNA chains. Most of their biological activity is triggered when proteins undergo configurational phase transitions form disordered random-coil structures to quasicrystalline highly compact three-dimensional structures known as native states. Given the vast number of potential conformations, the acquisition of an ordered structure from a disordered ensemble poses several challenges and it is an excellent arena to be discussed to the light of statistical mechanics based models. To the present, very few analytical solvable models of this kind are known since most of the main stream has concentrated on numerical and computational approaches to treat the protein-water and protein-protein interacting Hamiltonians. However, can we learn something about order-disorder phase transitions in these systems from basic models?

In this talk I shall focus the attention to a particular class of statistical mechanics based coarse grained models developed for homo and heteropolymer chains. These models admitt a full analytical solution for the equilibrium partition function Z. The first part of the talk will be centered around the mathematical and physical background related to the model. During the second part, results concerning the functional form of specific heat Cv and configurational entropy S for specific heteropolymer proteinogenic chains will be addressed. Some preliminary results about the influence of single-point mutations in the overall transition temperatures will be discussed at the end.