Nucleic Acids Research, Vol 24, Issue 16 3261-3266, Copyright © 1996 by Oxford University Press
AP White, KK Reeves, E Snyder, J Farrell, JW Powell, V Mohan and RH Griffey
Infrared spectroscopy was used to identify hydration-sensitive structural
differences between single- stranded phosphorothioate (PS) and
phosphodiester (PO) oligodeoxyribonucleotides. Spectra were recorded in the
mid-infrared region, 500-1800 cm-1, at relative humidities between 0 and
98%; the PS and PO spectra are substantially different. The hydration
effects on spectral bands in these single- stranded
oligodeoxyribonucleotides is markedly different from such behavior in
double- and triple-stranded oligodeoxyribonucleotides. A strong absorption
occurs at 656 cm-1 in the phosphorothioate sample which is completely
absent from the PO spectra. Gravimetric measurements were carried out on
one PS and one PO sample to monitor and confirm hydration. The calculated
BET adsorption constants [Brunauer, S., Emmett, RH. and Teller, E. (1938)
J. Am. Chem. Soc., 60, 309-319] are 1.2 and 1.4 water molecules per
nucleotide in the first hydration layer of PS and PO respectively. While
the gravimetric data indicate that the single-stranded
oligodeoxyribonucleotides hydrate very similarly to duplex DNA, the
mid-infrared conformational marker bands are strikingly different from
those observed for duplex DNA. In particular, the Vas of the phosphate
group (PO2) at 1222 cm-1 in the single-stranded PO spectra is independent
of relative humidity.
ARTICLES
Hydration of single-stranded phosphodiester and phosphorothioate oligodeoxyribonucleotides
Department of Physics, Reed College, Portland, OR 97202, USA.
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