Excess Electron Transfer in Flavin-Capped DNA-Hairpins

Abstract

DNA hairpins with an electron-acceptor molecule in the head region have recently allowed Lewis and Wasielewski to gain important insight into the hole conductivity of double helical DNA. In light of our current interest in deciphering the excess electron transport properties of double helical DNA, we evaluate in this report three different flavin molecules for their ability to form a stable DNA hairpin cap. The intention was to construct novel DNA hairpins in which the flavin chromophore is perfectly stacked on top of the final base pair. A solid-phase synthesis protocol was devised for the incorporation of the three flavin-H-phosphonates into oligonucleotides using a mixed phosphoramidite/H-phosphonate/phosphoramidite protocol. We describe here that all three flavin-cap molecules yield stable DNA hairpins. UV, fluorescence and melting temperature studies showed that one of the three flavins is stacked in the intended fashion. Initial studies show that the flavin in the reduced and deprotonated state can indeed inject an electron into the hairpin. This flavin-capped DNA hairpin allows a detailed investigation of the excess electron transfer capabilities of double helical DNA. (© Wiley-VCH Verlag GmbH, 69451 Weinheim, Germany, 2002)