Fluorescence quantum yield measurements: vitamin B6 compounds.

Quantum yields for pyridoxal, pyridoxamine, and pyridoxamine-5-phosphate at 25 degrees C in neutral aqueous solution were 0.048, 0.11, and 0.14, respectively. The fluorescence efficiencies were highly temperaturedependent, and the compounds were extremely sensitive to light. There were marked discrepancies between the values obtained in this study for quantum yield and fluorescence polarization of pyridoxamine-5-phosphate and the values recently reported by others.