title: Thin-film properties of DNA and RNA bases: a combined experimental and theoretical study.
abstract: The structures of the DNA and RNA bases cytosine, uracil, and thymine in thin films with a nominal film thickness of about 20 nm are studied by using X-ray photoemission spectroscopy (XPS) and Fourier-transform infrared spectroscopy. The molecules are evaporated in situ from powder on a gold foil. The experimental results indicate that cytosine is composed of two energetically close tautomeric forms, whereas uracil and thymine exist in only one tautomeric form. Additionally, quantum chemical calculations are performed to complement the experimental results. The relative energies of the tautomeric forms of cytosine, uracil, and thymine are calculated using Hartree-Fock (HF), density functional theory (DFT), and post-HF methods. Furthermore, the assignment of the XPS spectra is supported by using simple model considerations employing Koopmans ionization energies and Mulliken net atomic charges.
authors.affiliation: Physical Chemistry, University of Tübingen, Auf der Morgenstelle 8, 72076 Tübingen, Germany.
authors.forename: Andrea
authors.initials: A
authors.lastname: Haug
authors.forename: Sabine
authors.initials: S
authors.lastname: Schweizer
authors.forename: Florian
authors.initials: F
authors.lastname: Latteyer
authors.forename: Maria Benedetta
authors.initials: MB
authors.lastname: Casu
authors.forename: Heiko
authors.initials: H
authors.lastname: Peisert
authors.forename: Christian
authors.initials: C
authors.lastname: Ochsenfeld
authors.forename: Thomas
authors.initials: T
authors.lastname: Chassé
mesh_terms: D003596:Cytosine / Q000737:chemistry*; D004247:DNA; D008958:Models, Molecular; D015394:Molecular Structure; D049329:Nanostructures / Q000737:chemistry*; D012313:RNA; D017550:Spectroscopy, Fourier Transform Infrared; D013057:Spectrum Analysis; D013941:Thymine / Q000737:chemistry*; D014498:Uracil / Q000737:chemistry*; D014965:X-Rays
chemical_list: D014498:Uracil; D012313:RNA; D003596:Cytosine; D004247:DNA; D013941:Thymine