Detection of the excited singlet state of a deprotonated, reduced flavin.

The excited singlet state of a deprotonated, reduced flavin [1,5-dihydro-N(3)-carboxymethyllumiflavin] in aqueous solution at pH 8 has been detected by laser flash photolysis. The broad absorption band maximized at approximately 490 nm (epsilon = 9.9 x 10(3) M-1 cm-1). The lifetime of the transient was found to be 100 +/- 15 ps. The lifetime was not affected by the presence of pyrimidine dimers, which would be monomerized under these conditions. A longer-lived transient, tentatively identified as the solvated electron, was also detected. The neutral reduced flavin did not give a detectable transient.