title: The structure of the protonated adenine dimer by infrared multiple photon dissociation spectroscopy and electronic structure calculations.
abstract: The infrared multiple photon dissociation (IRMPD) spectrum of electrosprayed adenine proton-bound dimers were recorded in the gas-phase inside the cell of a Fourier transform ion cyclotron resonance spectrometer coupled to a tunable optical parametric oscillator/amplifier infrared laser. While gas-phase B3LYP/6-31+G(d,p) calculations indicate that the four lowest isomers are essentially isoenergetic, comparisons of the experimental and predicted IR spectra suggest that only two of the four isomers are observed in the experiment. However, computed solvation effects, as modeled using both a polarizable continuum model and microsolvation with five explicit water molecules, preferentially stabilize these two observed isomers, consistent with the interpretation of the IRMPD spectra. This work shows that for these small species the solvent-phase structure is preserved. It also demonstrates the potential danger of using gas-phase calculations to predict the structures of gaseous ions born in solution, such as those from an electrospray source.
authors: Department of Chemistry, Memorial University of Newfoundland, St. John's, Newfoundland, Canada, A1B 3X7.
authors: Khadijeh
authors: K
authors: Rajabi
authors: Kelly
authors: K
authors: Theel
authors: Elizabeth A L
authors: EA
authors: Gillis
authors: Gregory
authors: G
authors: Beran
authors: Travis D
authors: TD
authors: Fridgen
mesh_terms: D000225:Adenine / Q000737:chemistry*; D003198:Computer Simulation; D019281:Dimerization; D005740:Gases / Q000737:chemistry; D008958:Models, Molecular; D015394:Molecular Structure; D044367:Phase Transition; D011522:Protons; D012997:Solvents / Q000737:chemistry; D013055:Spectrophotometry, Infrared; D013816:Thermodynamics; D014867:Water / Q000737:chemistry
chemical_list: D005740:Gases; D011522:Protons; D012997:Solvents; D014867:Water; D000225:Adenine