Ultraviolet difference spectral studies in the gamma radiolysis of DNA and model compounds. I. Aqueous solutions of DNA bases.
Ultraviolet difference spectra of gamma-irradiated, air-saturated aqueous solutions of DNA bases vs. unirradiated solutions of the same bases are shown to be a very sensitive supplemental tool with which to investigate the yields, postirradiation kinetics, and general nature of DNA base radiation products. Irradiated pyrimidines yield difference spectra which are approximately negative mirror-images of the base absorption spectra in the near-UV, indicating loss of ring conjugation. Difference spectra of irradiated purines yield a more complex pattern containing a positive long-wavelength peak, interpreted as radiation-induced extension of conjugation of the pi electron system beyond that of the unirradiated purine. On the basis of the spectroscopic evidence from these studies, 8-hydroxyguanine appears to be the dominant UV-absorbing radiation product in air-saturated guanine solutions with a G-value of 0.3 molec (100 eV)-1. Difference spectral studies provide isosbestic points which can be used in testing proposed radiation products and their yields. Such spectral studies are a rapid, non-invasive, supplemental tool which can be employed in conjunction with other analytical techniques in radiation-chemical studies, and which is one of the few tools able to detect short-lived chemical intermediates observed in oxygenated solutions of irradiated purines.
Trumbore
C N
CN
Department of Chemistry and Biochemistry, University of Delaware, Newark 19716.
Hyde
C T
CT
Hudson
R D
RD
Jurman
L A
LA
Gehring
A G
AG
Masselink
J K
JK
D000225:Adenine / Q000528:radiation effects*; D003037:Cobalt Radioisotopes; D003596:Cytosine / Q000528:radiation effects*; D005720:Gamma Rays; D006147:Guanine / Q000528:radiation effects*; D012996:Solutions; D013056:Spectrophotometry, Ultraviolet; D013941:Thymine / Q000528:radiation effects*; D014867:Water
D003037:Cobalt Radioisotopes; D012996:Solutions; D014867:Water; D006147:Guanine; D003596:Cytosine; D000225:Adenine; D013941:Thymine