Gas Phase Structure of Metal Mediated (Cytosine)2Ag+ Mimics the Hemiprotonated (Cytosine)2H+ Dimer in i-Motif Folding

M. BERDAKIN; V. STEINMETZ; P. MAITRE; G. A. PINO

JOURNAL OF PHYSICAL CHEMISTRY A

AMER CHEMICAL SOC

Lugar: Washington; Año: 2014 vol. 118 p. 3804 - 3809

1089-5639

The study of metal ion-DNA interaction aiming to understand the stabilization of artificial base pairing and a number of non canonical 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 hetero-nitrogen atoms in each Cytosine (both in the keto-amino form). This structure is biological 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 duplex in the DNA i-motif structure.