Deuterium isotope effect on excited-state dynamics in an alternating GC oligonucleotide.

Isotope effects on the excited-state dynamics of single- and double-stranded GC-containing DNAs were studied by femtosecond transient absorption spectroscopy. A pronounced deuterium isotope effect was observed in alternating d(GC)(9).d(GC)(9), but none was seen in the nonalternating or single-stranded variations investigated. These findings demonstrate that an interstrand process involving proton-coupled electron transfer contributes to the excited-state dynamics in DNAs having an appropriate base sequence.