title: Excited-state hydrogen atom abstraction initiates the photochemistry of β-2'-deoxycytidine.
abstract: Understanding the effects of ultraviolet radiation on nucleotides in solution is an important step towards a comprehensive description of the photochemistry of nucleic acids and their constituents. Apart from having implications for mutagenesis and DNA photoprotection mechanisms, the photochemistry of cytidines is a central element in UV-assisted syntheses of pyrimidine nucleotides under prebiotically plausible conditions. In this contribution, we present UV-irradiation experiments of β-2'-deoxycytidine in aqueous solution involving H-D exchange followed by NMR spectroscopic analysis of the photoproducts. We further elucidate the outcome of these experiments by means of high-level quantum chemical calculations. In particular, we show that prolonged UV-irradiation of cytidine may lead to H-C1' hydrogen atom abstraction by the carbonyl oxygen atom of cytosine. This process may enable photoanomerisation and nucleobase loss, two previously unexplained photoreactions observed in pyrimidine nucleotides.
authors.affiliation: Institute of Biophysics, Academy of Sciences of the Czech Republic, Královopolská 135, 61265, Brno, Czech Republic. rafal.szabla@gmail.com.
authors.forename: Rafał
authors.initials: R
authors.lastname: Szabla
authors.affiliation: School of Chemistry, The University of Manchester, Oxford Road, Manchester M13 9PL, UK; Inorganic Chemistry Laboratory, Department of Chemistry, University of Oxford, South Parks Road, Oxford OX1 3QR, UK.
authors.forename: Jesús
authors.initials: J
authors.lastname: Campos
authors.affiliation: Institute of Biophysics, Academy of Sciences of the Czech Republic, Královopolská 135, 61265, Brno, Czech Republic. rafal.szabla@gmail.com; CEITEC - Central European Institute of Technology, Masaryk University, Campus Bohunice, Kamenice 5, CZ-62500 Brno, Czech Republic.
authors.forename: Judit E
authors.initials: JE
authors.lastname: Šponer
authors.affiliation: Institute of Biophysics, Academy of Sciences of the Czech Republic, Královopolská 135, 61265, Brno, Czech Republic. rafal.szabla@gmail.com; CEITEC - Central European Institute of Technology, Masaryk University, Campus Bohunice, Kamenice 5, CZ-62500 Brno, Czech Republic.
authors.forename: Jiřĺ
authors.initials: J
authors.lastname: Šponer
authors.affiliation: Theoretical Chemistry Group, Institute of Physical and Theoretical Chemistry, Wroclaw University of Technology, Wybrzeże Wyspiańskiego 27, 50-370 Wroclaw, Poland. robert.gora@pwr.edu.pl.
authors.forename: Robert W
authors.initials: RW
authors.lastname: Góra
authors.affiliation: MRC Laboratory of Molecular Biology, Hills Road, Cambridge, CB2 0QH, UK. johns@mrc-lmb.cam.ac.uk.
authors.forename: John D
authors.initials: JD
authors.lastname: Sutherland