Resonance Raman spectroscopy of pyridoxal Schiff bases.

Resonance Raman (RR) spectra are reported for amino acid and amine adducts of pyridoxal 5'-phosphate (PLP) and 5'-deoxypyridoxal (5'-dPL) in aqueous solution. For the valine adducts, a detailed study has been carried out on solutions at pH and pD 5, 9, and 13, values at which the pyridine and imine protons are successively ionized, and on the adducts formed from 15N-valine, alpha-deuterovaline, and N-methyl-PLP. Good quality spectra were obtained, despite the strong fluorescence of pyridoxal Schiff bases, by adding KI as a quencher, and by exciting the molecules on the blue side of their absorption bands: 406.