Drastic enhancement of excess electron-transfer efficiency through DNA by inserting consecutive 5-phenylethynyl-2'-deoxyuridines as a modulator.

5-(Phenylethynyl)-2'-deoxyuridine ((Ph)U) was consecutively incorporated into oligodeoxynucleotides as an electron transport modulator for regulating DNA-mediated excess electron transfer (EET). Upon photoexcitation of the ethynylpyrene chromophore, extremely high EET efficiencies through DNA containing consecutive (Ph)Us were observed using 5-bromouracil as a distal electron trap.

Enhancement of fluorescence quenching and exciplex formation in DNA major groove by double incorporation of modified fluorescent deoxyuridines.

5-(1-Naphthalenylethynyl)-2'-deoxyuridine ((N)U) and 5-[(4-cyano-1-naphthalenyl)ethynyl]-2'-deoxyuridine ((CN)U) were synthesized and incorporated into oligodeoxynucleotides. Fluorescence emissions of modified duplexes containing double (N)U were efficiently quenched depending upon the sequence pattern of the naphthalenes in DNA major groove, as compared to the duplex possessing single (N)U. When one of the naphthalene moieties has a cyano substituent, the exciplex emission from the chromophores in DNA major groove was observed at longer wavelength.