Internal conversion to the electronic ground state occurs via two distinct pathways for pyrimidine bases in aqueous solution.

ABSTRACT: The femtosecond transient absorption technique was used to study the relaxation of excited electronic states created by absorption of 267-nm light in all of the naturally occurring pyrimidine DNA and RNA bases in aqueous solution. The results reveal a surprising bifurcation of the initial excited-state population in <1 ps to two nonradiative decay channels within the manifold of singlet states. The first is the subpicosecond internal conversion channel first characterized in 2000. The second channel involves passage through a dark intermediate state assigned to a lowest-energy (1)npi* state. Approximately 10-50% of all photoexcited pyrimidine bases decay via the (1)npi* state, which has a lifetime of 10-150 ps. Three- to 6-fold-longer lifetimes are seen for pyrimidine nucleotides and nucle

SUBMITTER: Hare PM 

PROVIDER: S-EPMC1766402 | biostudies-literature | 2007 Jan

REPOSITORIES: biostudies-literature