PHOTOINDUCED GENERATION OF THE RIBOFLAVIN-TRYPTOPHAN ADDUCT AND A VIBRATIONAL INTERPRETATION OF ITS STRUCTURE

A pure fraction of a riboflavin-tryptophan adduct was obtained for the first time from a mixture of products resulting from the anaerobic ph otoirradiation of riboflavin and tryptophan in solution. The procedure used to isolate the adduct is described. Characterization of the comp ound was performed by using absorption spectra and fluorescence measur ements. A vibrational interpretation of the structure of this adduct w as performed on the basis of its infrared spectrum. The vibrational as signment suggests an important electronic redistribution in the struct ure of riboflavin and tryptophan when the adduct is formed. From this fact can be inferred at least two ways of binding between the indole a nd isoalloxazine rings. Stability of the adduct is also discussed.