Effects of hydrogen bonding on the UV resonance Raman bands of the adenine ring and its C8-deuterated analog

Ultraviolet (UV) resonance Raman spectra of an acetyl derivative of adenosine and its C8-deuterated analog were measured in solvents with varied hydrogen bonding properties. The Raman spectrum of the acetyl derivative in H2O solution is almost identical to that of adenosine in H2O solution, indicating that the acetyl derivative is a good model for the adenine nucleotide in DNA, Most of the Raman bands increase or decrease in wavenumber upon hydrogen bonding at the proton-donor (C6-NH2) and proton-acceptor sites (N1, N3 and N7) of the adenine ring. Among them, the nu(1), nu(2), nu(3), nu(5) and nu(9) bands of the adenine ring and the nu(1)', nu(2)', nu(3)', nu(5)', nu(7)' and nu(9)' bands of the C8-deuterated adenine ring show wavenumber shifts larger than 5 cm(-1). Relative intensities of some Raman bands change as well. The wavenumber and intensity changes can be used as markers of hydrogen bonding at the proton donor and/or acceptor sites of the adenine ring. The Raman spectral difference between the nondeuterated and C8-D labeled adenine rings reflects the hydrogen-bonding state very sensitively and is expected to be useful in studying the hydrogen-bonding state of a particular adenine residue in oligonucleotides by a combination of site-selective C8-D labeling and UV resonance Raman spectroscopy. (C) 1998 Elsevier Science B.V. All rights reserved.