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Anomalous power law decay in solvation dynamics of DNA: a mode coupling theory analysis of ion contribution

Bagchi, Biman (2014) Anomalous power law decay in solvation dynamics of DNA: a mode coupling theory analysis of ion contribution. In: MOLECULAR PHYSICS, 112 (9-10). pp. 1418-1426.

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Official URL: http://dx.doi.org/10.1080/00268976.2014.904943

Abstract

Several time dependent fluorescence Stokes shift (TDFSS) experiments have reported a slow power law decay in the hydration dynamics of a DNA molecule. Such a power law has neither been observed in computer simulations nor in some other TDFSS experiments. Here we observe that a slow decay may originate from collective ion contribution because in experiments DNA is immersed in a buffer solution, and also from groove bound water and lastly from DNA dynamics itself. In this work we first express the solvation time correlation function in terms of dynamic structure factors of the solution. We use mode coupling theory to calculate analytically the time dependence of collective ionic contribution. A power law decay in seen to originate from an interplay between long-range probe-ion direct correlation function and ion-ion dynamic structure factor. Although the power law decay is reminiscent of Debye-Falkenhagen effect, yet solvation dynamics is dominated by ion atmosphere relaxation times at longer length scales (small wave number) than in electrolyte friction. We further discuss why this power law may not originate from water motions which have been computed by molecular dynamics simulations. Finally, we propose several experiments to check the prediction of the present theoretical work.

Item Type: Journal Article
Additional Information: copyright for this article belongs to TAYLOR & FRANCIS LTD, 4 PARK SQUARE, MILTON PARK, ABINGDON OX14 4RN, OXON, ENGLAND
Keywords: DNA hydration dynamics; power law decay; wave number-dependent ion atmosphere relaxation; Debye-Falkenhagen effect
Department/Centre: Division of Chemical Sciences > Solid State & Structural Chemistry Unit
Depositing User: Id for Latest eprints
Date Deposited: 24 Jun 2014 06:00
Last Modified: 26 Jun 2014 05:47
URI: http://eprints.iisc.ac.in/id/eprint/49301

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