Berlin 2001 – wissenschaftliches Programm
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MO: Molekülphysik
MO 14: Spektroscopy II
MO 14.11: Vortrag
Freitag, 6. April 2001, 18:15–18:30, H1058
Laser spectroscopy of pair formation by isolated nucleobases in the absence of the DNA backbone — •Karl Kleinermanns1, Mattanjah de Vries2, Eyal Nir3, Petra Imhof1, and Christoph Janzen1 — 1Heinrich-Heine Universit/"at D/"usseldorf 40225 D/"usseldorf Universit/"atsstr. 26.43.02 — 2University of California, Santa Barbara, CA 93106, USA — 3The Hebrew University of Jerusalem, Jerusalem 91904
Observing the intrinsic way in which DNA bases form pairs requires separating them from their biological environment in order to distinguish properties due to the molecular structure itself from those externally imposed. The vibronic and IR spectra of the DNA base guanine (G) and the base pairs guanine-cytosine (GC) and guanine-guanine (GG) were obtained after laser desorption and jet cooling via UV-R2PI of the G chromophore and IR-UV and UV-UV double resonance spectroscopy of the different keto-enol tautomers of G and their clusters. The IR spectra in the range of the OH- and NH- stretch vibrations and the comparison with the UV and IR spectra of methylsubstituted G and C and its clusters(tautomerism blocked) allowed a complete assignment of the 3 tautomers of G and its clusters in the gas phase. Proton transfer between bases in a base-pair radical cation and subsequent reactions in the nucleotides are assumed to be a major source of damage of DNA by ionizing radiation. The electronic origin band of GC is observed as a spectral peak at the mass of CH+ (m/e=112) also. Obviously proton transfer weakens the bonding in the complex ion.