title: Microhydration of the guanine-guanine and guanine-cytosine base pairs.
abstract: Monohydration structures of the guanine-guanine and guanine-cytosine base pairs have been elucidated by IR-UV double resonance spectroscopy combined with ab initio calculations. The systems studied consist of the homodimer of 9-methylguanine and the heterodimer of 9-methylguanine and 1-methylcytosine in which the methyl group is introduced to mimic the presence of the sugar-phosphate backbone and to block specific tautomerization. The monohydrate of the homodimer is identified as that of the most stable symmetric structure formed by the keto tautomers of guanine, which demonstrates that the base pair structure is not influenced by the hydration. It is also shown that at least two structural isomers, one of which retains the Watson-Crick GC pair structure, contribute the monohydrated cluster of the heterodimer. Although stacked base pairs are suggested to be significantly stabilized by the addition of water, the result shows no clear indication for the presence of stacked monohydrates in either homodimer or heterodimer case.
authors.affiliation: Graduate School of Arts and Sciences, Yokohama City University, Yokohama 236-0027, Japan.
authors.forename: Shu-Hei
authors.initials: SH
authors.lastname: Urashima
authors.forename: Hiroya
authors.initials: H
authors.lastname: Asami
authors.forename: Masashi
authors.initials: M
authors.lastname: Ohba
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Saigusa
mesh_terms: D020029:Base Pairing; D003596:Cytosine / Q000031:analogs & derivatives* / Q000737:chemistry; D006147:Guanine / Q000031:analogs & derivatives* / Q000737:chemistry; D056004:Molecular Dynamics Simulation
chemical_list: C031532:1-methylcytosine; C116701:9-methylguanine; D006147:Guanine; D003596:Cytosine