title: Efficiency of [2 + 2] photodimerization of various stilbene derivatives within the DNA duplex scaffold.
abstract: A DNA duplex was used as a scaffold to evaluate the intrinsic reactivity of [2 + 2] photodimerization between stilbene derivatives; the duplex pre-organizes the substrates avoiding the need for an association step. Unmodified stilbenes were first introduced at base-pairing positions on complementary DNA strands. The duplex was then irradiated with 340 nm UV light. HPLC analyses revealed that [2 + 2] photodimerization proceeded rapidly without side reactions. Thus, it was confirmed that the DNA duplex could be used as an ideal scaffold for [2 + 2] photodimerization of stilbenes. Next, we examined homo-photodimerization abilities of various stilbene derivatives. Homo-photodimerization of p-cyanostilbene, p-methylstilbazolium, and p-stilbazole occurred efficiently, whereas homo-photodimerization of p-dimethylaminostilbene and p-nitrostilbene did not proceed at all, probably because the reaction was quenched by dimethylamino and nitro groups. Time-dependent density functional theory calculations revealed that excitation energy was correlated with quantum yield. We further investigated hetero-photodimerization. These reactions were made possible by the use of two complementary oligodeoxyribonucleotides tethering different stilbene derivatives. Reactivities in hetero-photodimerization were highly dependent on the combination of derivatives. A high correlation was observed between the quantum yields and energy gaps of HOMO and LUMO between reactive derivatives. Unexpectedly, nitrostilbene, which was non-reactive in homo-photodimerization, cross-reacted with p-methylstilbazolium and p-stilbazole, both of which had close HOMO or LUMO with nitrostilbene. Evaluation of the intrinsic reactivity of homo- and hetero-photodimerization of stilbene derivatives was made possible by the use of DNA as a scaffold.
authors.affiliation: Graduate School of Engineering, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, 464-8603, Japan. asanuma@nubio.nagoya-u.ac.jp kashida@nubio.nagoya-u.ac.jp.
authors.forename: Tetsuya
authors.initials: T
authors.lastname: Doi
authors.forename: Hiromu
authors.initials: H
authors.lastname: Kashida
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Asanuma
mesh_terms: D020029:Base Pairing; D004247:DNA / Q000737:chemistry*; D019281:Dimerization; D008958:Models, Molecular; D009690:Nucleic Acid Conformation; D009838:Oligodeoxyribonucleotides / Q000737:chemistry*; D055668:Photochemical Processes; D013267:Stilbenes / Q000737:chemistry*; D014466:Ultraviolet Rays
chemical_list: D009838:Oligodeoxyribonucleotides; D013267:Stilbenes; D004247:DNA