Ionization of purine tautomers in nucleobases, nucleosides, and nucleotides: from the gas phase to the aqueous environment
Language English Country United States Media print-electronic
Document type Journal Article, Research Support, Non-U.S. Gov't, Research Support, U.S. Gov't, Non-P.H.S.
PubMed
21247073
DOI
10.1021/jp110388v
Knihovny.cz E-resources
- MeSH
- Models, Chemical MeSH
- Quantum Theory MeSH
- Models, Molecular MeSH
- Nucleosides chemistry MeSH
- Nucleotides chemistry MeSH
- Gases chemistry MeSH
- Purines chemistry MeSH
- Thermodynamics MeSH
- Water chemistry MeSH
- Publication type
- Journal Article MeSH
- Research Support, Non-U.S. Gov't MeSH
- Research Support, U.S. Gov't, Non-P.H.S. MeSH
- Names of Substances
- Nucleosides MeSH
- Nucleotides MeSH
- Gases MeSH
- purine MeSH Browser
- Purines MeSH
- Water MeSH
We have simulated ionization of purine nucleic acid components in the gas phase and in a water environment. The vertical and adiabatic ionization processes were calculated at the PMP2/aug-cc-pVDZ level with the TDDFT method applied to obtain ionization from the deeper lying orbitals. The water environment was modeled via microsolvation approach and using a nonequilibrium polarizable continuum model. We have characterized a set of guanine tautomers and investigated nucleosides and nucleotides in different conformations. The results for guanine, i.e., the nucleic acid base with the lowest vertical ionization potential, were also compared to those for the other purine base, adenine. The main findings of our study are the following: (i) Guanine remains clearly the base with the lowest ionization energy even upon aqueous solvation. (ii) Water solvent has a strong effect on the ionization energetics of guanine and adenine and their derivatives; the vertical ionization potential (VIP) is lowered by about 1 eV for guanine while it is ∼1.5 eV higher in the nucleotides, overall resulting in similar VIPs for GMP(-), guanosine and guanine in water. (iii) Water efficiently screens the electrostatic interactions between nucleic acid components. Consequently, ionization in water always originates from the base unit of the nucleic acid and all the information about conformational state is lost in the ionization energetics. (iv) The energy splitting between ionization of the two least bound electrons increases upon solvation. (v) Tautomerism does not contribute to the width of the photoelectron spectra in water. (vi) The effect of specific short-range interactions with individual solvent molecules is negligible for purine bases, compared to the long-range dielectric effects of the aqueous medium.
References provided by Crossref.org
Specific versus Nonspecific Solvent Interactions of a Biomolecule in Water
