Albany 2015:Book of Abstracts
June 9-13 2015
©Adenine Press (2012)
The helix-coil transition in two-component solvent in the frames of GMPC. Ligands effects on the characteristics of the transition
Within the framework of the Generalized Model of the Polypeptide Chain (GMPC)( (Hairyan et al. (1990), (1995); Morozov et al. (2004)), we studied the effect of ligands interacting in various ways on the helix-coil transition. The most general case, where for each type of interaction, there are several sites for ligand or solvent molecules was considered. It has been shown that the model can be reduced to the base one by redefinition of energy and entropy parameters, and in contrast to the pure solvent case (Badasyan et al. (2014)) both parameters are affected by competitive and non-competitive interactions. As a result, the temperature behavior of the system in a two-component environment richer transitions transitions compared to a single component. It was also shown that a change in the concentration of ligand in the solvent transition temperature varies monotonically from the transition point of pure solvent to the transition point of pure ligand according to the expression
are equations for definition of melting temperature for pure solvent and ligand correspondingly.
Our results allow to explain the experimental results concerning the stabilization of polyalanine by polyethylene glycol (Koutsioubas et al. (2012)) at the microscopic level. Our theoretical results can be interpreted as follows. Water compete for hydrogen bond formation. Despite the fact that the ligand does not interact, but prevents this competition taking up space, leading to stabilization.
This research has been supported by 13-1F343 Grant from State Committee of Science Ministry of Education and Science of Armenia.
Hairyan, Sh.A., Mamasakhlisov, E.Sh. & Morozov, V.F. (1995). The helix-coil transition in polypeptides: a microscopic approach. II. Biopolymers, 35(1), 75-84.
Morozov, V.F., Badasyan, A.V., Grigoryan, A.V., Sahakyan, M.A., & Mamasakhlisov, Y.Sh. (2004).Stacking and hydrogen bonding: DNA cooperativity at melting. Biopolymers, 75,434-439.
Badasyan, A.V., Tonoyan, Sh. A., Giacometti, A., Podgornik, R., Parsegian, V. A., Mamasakhlisov, Y. Sh., & Morozov , V. F. (2014). Unified description of solvent effects in the helix-coil transition. Physical Review E, 89, 022723.
Koutsioubas, A., Lairez, D., Combet, S., Fadda, G. C., Longeville, S., & Zalczer, G. (2012). Crowding effect on helix-coil transition: beyond entropic stabilization. Journal of Chemical Physics, 136 , 215101.
Arevik V. Asatryan
Department of Molecular Physics