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Albany 2019: 20th Conversation - Abstracts

category image Albany 2019
Conversation 20
June 11-15 2019
Adenine Press (2019)

Concentrational dependence of melting temperature: possible explanation of non-monotonic behavior

Biological macromolecules are mostly studied in aqueous solutions in presence of other compounds (ligands) dissolved in it [1-4]. It is meaningful theoretically to consider biopolymer in a two-component solvent. Our past studies in the frame of GMPC [1,2] resulted in the following expression for the concentration (c) dependence of helix-coil transition temperature (Tm)

equation-1.gif

Where {PL} and {PS} are sets of parameters describing the interaction of ligand and solvent with repeating unit correspondingly. Besides the variety of interaction schemes considered, Tm(c) resulting from Eq.1 always remains monotonic. Meantime, several experimental studies [3, 4] reported the non-monotonic behavior. In order to reproduce such non-monotonicity, we had to separate the binding sites for each of the solvent components in the model. To simplify, let us consider the case, when both components (e.g. water and intercalating ligands in the case of DNA) stabilize the helical structure. The Hamiltonian of such model is comprised of three terms: one for the base model [1], and two terms, describing the interactions with two components.

Two solvents terms in the Hamiltonian are organized in such a way to take into account the above-mentioned separation of binding sites. As before [1, 2], the model including solvents is reduced to the base model by the redefinition of parameters. Repeating the same analysis as for Eq.1, we arrive at non-monotonic Tm(c) ~ c2 dependence. In this particular case two stabilizing tendencies can result in the appearance of the maximum on Tm(c) . Thus our results allow to explain the appearance of the extremum on the stability curve without invoking the existence of two opposing mechanisms.

References

    A. Badasyan, Sh. Tonoyan, A. Giacometti, R. Podgornik, V. Parsegian, Y. Mamasakhlisov & V. Morozov (2014). Unified description of solvent effects in the helix-coil transition. Physical Review E, 89(2), 022723.

    A. Asatryan, Sh. Tonoyan, S. Mirtavoosi, Y. Mamasakhlisov & V. Morozov (2015). 192 The helix-coil transition in two-component solvent in the frames of GMPC. Ligands effects on the characteristics of the transition. Journal of Biomolecular Structure and Dynamics, 33(sup1), 126-127.

    P. Vardevanyan, A. Antonyan, M. Parsadanyan, M. Torosyan & A. Karapetian (2016). Joint interaction of ethidium bromide and methylene blue with DNA. The effect of ionic strength on binding thermodynamic parameters. Journal of Biomolecular Structure and Dynamics, 34(7), 1377-1382.

    N. De Costa J. & Heemstra (2013). Evaluating the effect of ionic strength on duplex stability for PNA having negatively or positively charged side chains. PloS one, 8(3), e58670.

A. Asatryan
Sh. Tonoyan
Y. Mamasakhlisov
V. Morozov

Department of Molecular Physics
Yerevan State University {PS}

Ph: (374) 60-710-322
Fx: (374) 10554-641
Email: asarevik@gmail.com