Program

O.7 -- Oral, NCTP-41

Date: Monday, 1 August 2016

Time: 14h40 - 15h00

Grand-canonical Monte-Carlo simulation of salt mixtures and an application to study osmotic pressure of DNA bundle

Nguyen Viet Duc (2), Nguyen The Toan (1,2,3), Nguyen Huu Duc (4)

(1) VNU Key Laboratory for Multiscale Simulation of Complex Systems,Vietnam National University, 334 Nguyen Trai Street, ThanhXuan, Hanoi, Vietnam (2) Faculty of Physics, Hanoi University of Science, Vietnam National University, 334 Nguyen Trai Street, Thanh Xuan, Hanoi, Vietnam (3) School of Physics, Georgia Institute of Technology, 837 State Street, Atlanta, Georgia 30332-0430, USA (4) VNU Key Laboratory for Micro-nano Technology, Vietnam National University, 144 Xuan Thuy Street, Cau Giay, Hanoi, Vietnam

A Grand-canonical Monte-Carlo simulation method extended to simulate a mixture of salts using primitive ion models is presented. The fugacities for different salts or salts mixtures at different concentrations are reported. The results are applied to study numerically the osmotic pressure of DNA hexagonal bundle in equilibrium with a bulk solution of salt mixture of monovalent and divalent counterions. Experimentally, it is know, that multivalent counterions have strong effect on the DNA condensation phenomenon. While tri- and tetra-valent counterions are shown to easily condense free DNA molecules in solution into toroidal bundles. Some divalent counterions like $Mg^{+2}$ are not able to condense free DNA molecules in solution, while some like $Mn^{+2}$ can condense them into disorder bundles. In restricted environment such as in two dimensional system or inside viral capsid, $Mg^{+2}$ can have strong effect and able to condense them, but the condensation varies qualitatively with different system, different coions. Our simulations show that, varying the divalent salt concentration and ion sizes has considerable effect on the osmotic pressure, in qualitative agreement with experimental results. This paper is to delicate to Dr. Peter Brommer -- a former physicist of the University of Amsterdam.

Presenter: Nguyen Viet Duc