Theoretical analysis of Raman and resonance Raman spectra of simple bases of nucleic acids

A theoretical analysis of the intensity distribution in Raman and resonance Raman spectra of simple bases of nucleic acids was made. Calculations of w avenumbers and line intensities in the Raman spectra of uracil and its deut erated analogues were carried out using the classical scheme in the valence -force approximation. In contrast, the intensity distribution in the resona nce Raman spectra of uracil excited by laser radiation of wavelength 266 an d 240 mn was calculated using a quantum-mechanical method. In both types of spectra the theoretical data showed good agreement with experimental resul ts. Two types of H-bonding in uracil were determined and the mechanism of H -bond formation is discussed, The electronic-vibrational interaction in ura cil was shown to be significant. The quantum-mechanical method using the He rzberg-Teller approximation is suitable for the analysis of the resonance R aman spectra of simple bases of nucleic acids. Copyright (C) 2000 John Wile y & Sons, Ltd.