Abnormal shifts in Raman spectra of deuterated cytidine and 6-azacytidine

S Garasevych,I Vaskivskyi,O Slobodyanyuk,M Iakhnenko

doi:10.1155/2010/107694

Abstract

It was revealed that some peaks in Raman spectra of cytidine, 6-azacytidine (6-azaC), and cytosine dissolved in D2O are shifted to high frequencies in respect to their positions in spectra of H2O solution. Such “blue shifts” occur due to deuteration of the nucleoside molecule itself but not due to effect of deuterated solvent. This conclusion is deduced from observation of blue (abnormal) shift in Raman spectra of cytidine and 6-azaC microcrystals recrystallized from D2O solution. Both normal and abnormal shifts close to the experimentally observed were obtained in the calculated spectra of 6-azaC and cytidine. We assume that abnormal shifts may be caused by substitution of intramolecular H-bonds with D-bonds.

Highlights

The cytidine is well-known canonical nucleoside and anomalous nucleoside 6-azacytidine (6-azaC) is a structural analogue thereof with N atom replacing of C–H group at the 6th position of pirimidine ring ([5] and references therein)
In this paper we present results of experimental and computational study of blue shift in Raman spectra of cytidine and 6-azaC
An increasing of mode frequency when reduced mass increases due to deuteration may be explained by advance strengthening of mode force constants

Summary

Introduction

The cytidine is well-known canonical nucleoside and anomalous nucleoside 6-azacytidine (6-azaC) is a structural analogue thereof with N atom replacing of C–H group at the 6th position of pirimidine ring ([5] and references therein). The 6-azaC is usually available in microcrystalline form but its valuable biological activity appears in solutions and not in crystalline state. Raman spectra of 6-azaC were measured for the first time both in microcrystalline form and in different in water H2O and D2O solutions [6]. Shifts of some Raman peaks of 6-azaC dissolved in D2O to high frequencies in respect to their position in H2O solution and microcrystalline spectra were noticed. Similar blue shift was observed in spectrum of cytidine dissolved in D2O. In this paper we present results of experimental and computational study of blue shift in Raman spectra of cytidine and 6-azaC

Materials and methods

Results and discussion

Conclusions