Photobinding and Photoreactivity of Riboflavin in the Presence of Macromolecules

The rate of aerobic photobleaching of riboflavin by visible light is considerably enhanced by the presence of macromolecules such as PVP, polysorbate 80, and sodium decyl sulfate. The catalysis by the macromolecules is attributed in part to a reversible binding of excited riboflavin molecules to macromolecules to produce longer-lived excited species. Methods are described which permit direct determination of enhanced binding of riboflavin to macromolecules during irradiation. Evidence is presented to indicate involvement of a triplet state in both the photobinding and the photodecomposition.