Raman spectroscopic study on the subpicosecond dynamics in calf-thymus DNA, upon lowering the pH and in the presence of Mn2 ionsReportar como inadecuado




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Spectroscopy - Volume 22 2008, Issue 6, Pages 475-489



National Institute of Research & Development for Isotopic and Molecular Technologies, Cluj-Napoca, Romania

National Institute of Research & Development for Isotopic and Molecular Technologies, P.O. 5, Box 700, R-400293 Cluj-Napoca, Romania



Copyright © 2008 Hindawi Publishing Corporation. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

In this paper the Raman total half bandwidths of calf-thymus DNA vibrations have been measured as a function of pH 3.45–6.4, in the presence of Mn

ions, respectively. The dependencies of the half bandwidths and of the global relaxation times, on DNA molecular subgroup structure and on pH, are reported. It is shown that changes in the subpicosecond dynamics of molecular subgroups in calf-thymus DNA can be monitored with Raman spectroscopy.

Particularly, the Raman band parameters for the vibrations at 728 cm

dA, 787 cm

dC, 1093 cm

PO2

, 1376 cm

dA, dG, dT, dC, 1489 cm

dG, dA and 1578 cm

dG, dA of MnDNA complexes, at reduced and low pH values, are presented. In our study, the full widths at half-maximum FWHM of the bands in calf-thymus DNA are typically in the wavenumber range from 11 to 27 cm

. It can be observed that the molecular relaxation processes studied in this work, have a global relaxation time smaller than 0.965 ps and larger than 0.393 ps. The limit values are characteristic for dA and dC residues, respectively vibrations at 728 and 787 cm

.

Low pH-induced melting of double helical structure in calf-thymus DNA, in the presence of Mn

ions, results for some bands in smaller global relaxation times, and larger bandwidths, respectively, as a consequence of the increased interaction of the base moieties with the solvent molecules. This behaviour is most evident for the bands at 787 cm

up to pH 3.8, at 1578 cm

up to pH 3.45 and is partially confirmed for the DNA backbone PO2

symmetric stretching vibration at 1093 cm

.

The fastest molecular dynamics was obtained for the adenine band at 728 cm

in the pH interval 3.45–3.8 global relaxation time 0.885 ps, for the cytosine ring breathing mode near 787 cm

around the pH 3.8 global relaxation time 0.393 ps, for the band at 1093 cm

in the pH interval 3.8–4.4 global relaxation time 0.518 ps and for the vibration near 1578 cm

at pH 3.45 global relaxation time 0.544 ps.

A comparison between different time scales of the vibrational energy transfer processes, characterizing the protonated MnDNA structural subgroups has been given.

We have found that metal ion's type and concentration are modulators for the subpicosecond dynamics of protonated DNA molecular subgroups.





Autor: Cristina M. Muntean and Ioan Bratu

Fuente: https://www.hindawi.com/



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