Resonance Raman and coherent anti-stokes Raman scattering spectra of flavin derivatives. Vibrational assignments and the zwitterionic structure of 8-methylamino-riboflavin.

Resonance Raman and coherent anti-stokes Raman scattering spectra are reported for flavins modified by deprotonation at N3 and by CH substitution for N1, N3 and N5, using laser excitation in resonance with the visible electronic transition. Vibrational shifts are used to make qualitative assignments of the observed vibrational modes. Both 8-CH3NH- and ionized 8-OH-riboflavin were found to give markedly different spectra patterns form flavin itself; this observation supports a partial zwitterionic structure for the 8-CH3NH derivatives.