Photoinduced electron transfer between flavin and tryptophan in a poly(vinyl alcohol) film

• Flavins undergo PET in the presence of tryptophan (Trp).
• PET of flavin-Trp in polymer films was investigated by time-resolved fluorescence.
• Our observations were described using the free energy change and specific interactions.

The fluorescence of an electronically excited dye is influenced by surrounding quenchers through photoinduced electron transfer. Flavins participate in many biochemical reactions and undergo photoinduced electron transfer in the presence of tryptophan. Using three flavins (lumiflavin, riboflavin, and flavin mononucleotide), we investigated the photoinduced electron transfer of flavin-tryptophan which were embedded in poly(vinyl alcohol) films. The decrease in the fluorescence lifetimes of flavins becomes significant as the tryptophan concentration increases. Furthermore, we used the rate constants obtained from the measured fluorescence lifetimes to describe our observations based on the free energy change of the reaction, specific interactions, and excluded effects for the photoinduced electron transfer processes.