Normal mode analysis of lumiflavin and interpretation of resonance Raman spectra of flavoproteins.

The normal modes of lumiflavin (10-methyliso-alloxazine) are analyzed with a valence force field constructed with bond length-stretching force constant correlations and bending and interaction force constants transferred from small ring molecules. Observed resonance Raman (RR) bands of flavin are assigned to calculate modes on the basis of frequency and isotope shift matching. The normal mode patterns confirm previous inferences, based on selective effective of chemical substitutions, of localization to certain regions of the molecule. These results are used to interpret the observed variability of the prominent RR bands among different flavoproteins on the basis of protein-isoalloxazine interactions.