Radicals produced by gamma-irradiation of hyperquenched glassy water containing 2'-deoxyguanosine-5'-monophosphate.
Hyperquenched glassy water (HGW) has been suggested as the best model for liquid water, to be used in low-temperature studies of indirect radiation effects on dissolved biomolecules (Bednarek et al. J. Am. Chem. Soc. 1996, 118, 9387). In the present work, these effects are examined by X-band electron spin resonance spectroscopy (ESR) in gamma-irradiated HGW matrix containing 2'-deoxyguanosine-5'-monophosphate. Analysis of the complex ESR spectra indicates that, in addition to OH(*) and HO2(*) radicals generated by water radiolysis, three species are trapped at 77 K:(i) G(C8)H(*) radical, the H-adduct to the double bond at C8; (ii) G(- *) radical anion, the product of electron scavenging by the aromatic ring of the base; and (iii) dR(-H)(*) radicals formed by H abstraction from the sugar moiety, predominantly at the C'5 position. We discuss the yields of the radicals, their thermal stability and transformations, as well as the effect of photobleaching. This study confirms our earlier suggestion that in HGW the H atom addition/abstraction products are created at 77 K in competition with HO2(*) radicals, in a concerted process following ionization of water molecule at L-type defect sites of the H-bonded matrix. The lack of OH(*) reactivity toward the solute suggests that the H-bonded structure in HGW is much more effective in recombining OH(*) radicals than that of aqueous glasses obtained from highly concentrated electrolyte solutions. Furthermore, complementary experiments for the neat matrix have provided evidence that HO2(*) radicals are not the product of H atom reaction with molecular oxygen, possibly generated by ultrasounds used in the process of sample preparation.
Staluszka
Justyna
J
Institute of Applied Radiation Chemistry, Technical University of Lodz, Wroblewskiego 15, 93-590 Lodz, Poland.
Steblecka
Malgorzata
M
Szajdzinska-Pietek
Ewa
E
Kohl
Ingrid
I
Salzmann
Christoph G
CG
Hallbrucker
Andreas
A
Mayer
Erwin
E
D003848:Deoxyguanine Nucleotides / Q000737:chemistry* / Q000528:radiation effects*; D004578:Electron Spin Resonance Spectroscopy / Q000379:methods; D005609:Free Radicals / Q000737:chemistry / Q000528:radiation effects; D005720:Gamma Rays; D006860:Hydrogen Bonding; D008280:Magnetics; D015394:Molecular Structure; D010100:Oxygen / Q000737:chemistry / Q000528:radiation effects; D038761:Photobleaching; D014867:Water / Q000737:chemistry*
D003848:Deoxyguanine Nucleotides; D005609:Free Radicals; D014867:Water; C007257:2'-deoxyguanosine 5'-phosphate; D010100:Oxygen