title: Gas Phase Structure of Metal Mediated (Cytosine)2Ag+Mimics the Hemiprotonated (Cytosine)2H+Dimer in i-Motif Folding.
abstract: The study of metal ion-DNA interaction aiming to understand the stabilization of artificial base pairing and a number of noncanonical motifs is of current interest, due to their potential exploitation in developing new technological devices and expanding the genetic code. A successful strategy has been the synthesis of metal-mediated base pairs, in which a coordinative bond to a central metal cation replaces a H-bond in a natural pair. In this work, we characterized, for the first time, the gas phase structure of the cytosine···Ag+···cytosine (C-Ag+-C) complex by means of InfraRed-MultiPhoton-Dissociation (IR-MPD) spectroscopy and theoretical calculation. The IR-spectrum was confidently assigned to one structure with the Ag+acting as a bridge between the heteronitrogen atoms in each cytosine (both in the keto-amino form). This structure is biologically relevant since it mimics the structure of the hemiprotonated C-H+-C dimer responsible for the stabilization of the i-motif structure in DNA, with the replacement of the NH···N bond by a stronger N···Ag+···N bond. Moreover, since the structure of the C-Ag+-C complex is planar, it allows an optimum intercalation between pairs of the two antiparallel strand duplex in the DNA i-motif structure.
authors.affiliation: INFIQC (CONICET - Universidad Nacional de Córdoba), Departamento de Fisicoquímica, Facultad de Ciencias Químicas, Centro Láser de Ciencias Moleculares, Universidad Nacional de Córdoba , Ciudad Universitaria, X5000HUA Córdoba, Córdoba, Argentina.
authors.forename: Matias
authors.initials: M
authors.lastname: Berdakin
authors.affiliation: Laboratoire de Chimie Physique, Université Paris Sud , UMR8000 CNRS, Faculté des Sciences, 91405 Orsay Cedex, France.
authors.forename: Vincent
authors.initials: V
authors.lastname: Steinmetz
authors.affiliation: Laboratoire de Chimie Physique, Université Paris Sud , UMR8000 CNRS, Faculté des Sciences, 91405 Orsay Cedex, France.
authors.forename: Philippe
authors.initials: P
authors.lastname: Maitre
authors.affiliation: INFIQC (CONICET - Universidad Nacional de Córdoba), Departamento de Fisicoquímica, Facultad de Ciencias Químicas, Centro Láser de Ciencias Moleculares, Universidad Nacional de Córdoba , Ciudad Universitaria, X5000HUA Córdoba, Córdoba, Argentina.
authors.forename: Gustavo A
authors.initials: GA
authors.lastname: Pino