Fluorescence resonance energy transfer between specific-labeled sites on DNA

Fluorescence resonance energy transfer on DNA has been studied for the estimation of distances between specific sites. Two kind of fluorophores, donor and acceptor, were incorporated on double-stranded DNA via phosphorothioate linkage (Sp, Rp, or racemic mixture). The thermal stability of labeled DNA's was slightly dependent on the stereochemical orientation of fluorophore, however all of the duplex structures were stable under the conditions for fluorescence study. The distances between donor and acceptor fluorophores, estimated from fluorescence energy transfer, generally agreed with the expected distance in a B-type DNA for the limiting distance.