title: Absorption by DNA single strands of adenine isolated in vacuo: the role of multiple chromophores.
abstract: The degree of electronic coupling between DNA bases is a topic being up for much debate. Here we report on the intrinsic electronic properties of isolated DNA strands in vacuo free of solvent, which is a good starting point for high-level excited states calculations. Action spectra of DNA single strands of adenine reveal sign of exciton coupling between stacked bases from blueshifted absorption bands (~3 nm) relative to that of the dAMP mononucleotide (one adenine base). The bands are blueshifted by about 10 nm compared to those of solvated strands, which is a shift similar to that for the adenine molecule and the dAMP mononucleotide. Desolvation has little effect on the bandwidth, which implies that inhomogenous broadening of the absorption bands in aqueous solution is of minor importance compared to, e.g., conformational disorder. Finally, at high photon energies, internal conversion competes with electron detachment since dissociation of the bare photoexcited ions on the microsecond time scale is measured.
authors.affiliation: Department of Physics and Astronomy, Aarhus University, Ny Munkegade 120, DK-8000 Aarhus C, Denmark.
authors.forename: Lisbeth Munksgaard
authors.initials: LM
authors.lastname: Nielsen
authors.forename: Sara Øvad
authors.initials: SØ
authors.lastname: Pedersen
authors.forename: Maj-Britt Suhr
authors.initials: MB
authors.lastname: Kirketerp
authors.forename: Steen Brøndsted
authors.initials: SB
authors.lastname: Nielsen
mesh_terms: D000042:Absorption; D000225:Adenine / Q000737:chemistry*; D004277:DNA, Single-Stranded / Q000737:chemistry*; D003838:Deoxyadenine Nucleotides / Q000737:chemistry; D004583:Electrons; D007477:Ions / Q000737:chemistry
chemical_list: D004277:DNA, Single-Stranded; D003838:Deoxyadenine Nucleotides; D007477:Ions; C012873:2'-deoxy-5'-adenosine monophosphate; D000225:Adenine