Electronic structure and spectroscopy of nucleic acid bases: Ionization energies, ionization-induced structural changes, and photoelectron spectra

Journal Article · Mon Aug 02 00:00:00 EDT 2010 · Journal of Physical Chemistry A

DOI:https://doi.org/10.1021/jp1063726· OSTI ID:1001048

Bravaya, Ksenia B; Kostko, Oleg; Dolgikh, Stanislav; Landau, Arie; Ahmed, Musahid; Krylov, Anna I

We report high-level ab initio calculations and single-photon ionization mass spectrometry study of ionization of adenine (A), thymine (T), cytosine (C) and guanine (G). For thymine and adenine, only the lowest-energy tautomers were considered, whereas for cytosine and guanine we characterized five lowest-energy tautomeric forms. The first adiabatic and several vertical ionization energies were computed using equation-of-motion coupled-cluster method for ionization potentials with single and double substitutions. Equilibrium structures of the cationic ground states were characterized by DFT with the {omega}B97X-D functional. The ionization-induced geometry changes of the bases are consistent with the shapes of the corresponding molecular orbitals. For the lowest-energy tautomers, the magnitude of the structural relaxation decreases in the following series G > C > A > T, the respective relaxation energies being 0.41, 0.32, 0.25 and 0.20 eV. The computed adiabatic ionization energies (8.13, 8.89, 8.51-8.67 and 7.75-7.87 eV for A,T,C and G, respectively) agree well with the onsets of the photoionization efficiency (PIE) curves (8.20 {+-} 0.05, 8.95 {+-} 0.05, 8.60 {+-} 0.05 and 7.75 {+-} 0.05 eV). Vibrational progressions for the S{sub 0}-D{sub 0} vibronic bands computed within double-harmonic approximation with Duschinsky rotations are compared with previously reported experimental photoelectron spectra.

• Research Organization: Ernest Orlando Lawrence Berkeley National Laboratory, Berkeley, CA (US)
• Sponsoring Organization: Chemical Sciences Division
• DOE Contract Number: AC02-05CH11231
• OSTI ID: 1001048
• Report Number(s): LBNL-4111E
• Journal Information: Journal of Physical Chemistry A, Journal Name: Journal of Physical Chemistry A Journal Issue: 46 Vol. 114; ISSN 1089-5639; ISSN 1520-5215
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
99 GENERAL AND MISCELLANEOUS
ADENINES
APPROXIMATIONS
CYTOSINE
EFFICIENCY
ELECTRONIC STRUCTURE
Electronic structure
spectroscopy
nucleic
acid
bases
Ionization
energies
ionization-induced
photoelectron
spectra
GEOMETRY
GROUND STATES
GUANINE
IONIZATION
IONIZATION POTENTIAL
MASS SPECTROSCOPY
NUCLEIC ACIDS
PHOTOIONIZATION
RELAXATION
SPECTRA
SPECTROSCOPY
THYMINE