Flavin 1, N 6 -ethenoadenine dinucleotide: dynamic and static quenching of fluorescence.

Flavin 1,N(6)-ethenoadenine dinucleotide (epsilonFAD) was prepared by the action of chloroacetaldehyde on flavin adenine dinucleotide. This compound, which has two potential fluorophores, epsilon-adenine and isoalloxazine, shows extremely efficient energy transfer from the former to the latter. The fluorescences of both moieties are greatly diminished in the intact molecule. Determination of the fluorescence yields and lifetimes leads to the conclusion that at 20 degrees in neutral aqueous solution epsilonFAD exists mainly (90%) as an internally complexed or stacked form.