Linked Life Data

1965722

Source:http://linkedlifedata.com/resource/pubmed/id/1965722

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
4-5
pubmed:dateCreated
1991-7-17
pubmed:abstractText
In situ photolysis at 20 degrees C (argon plasma light source, lambda approximately greater than 200 mm) of oxygen-free solutions containing 2 mM H2O2 and heat-denatured, single-stranded (ss)DNA from calf-thymus resulted in the ESR spectra of the 6-hydroxy-5,6-dihydro-thymin-5-yl (1) and 5-methyleneuracil (3) radicals linked to the sugar-phosphate backbone. They were generated by reaction of OH radicals with DNA. By comparison of the decay characteristics of the ESR signals with rate constants from pulse-conductivity measurements [E. Bothe, G.A. Qureshi and D. Schulte-Frohlinde, Z. Naturforsch., 38c, 1030, (1983)] the thymine-derived radicals (1) and (3) can be excluded as precursors of the fast, dominating component of strand breakage of ssDNA. In the absence of H2O2 from native, double-stranded (ds)DNA an ESR signal was obtained (singlet, g approximately 2.004, delta v1/2 approximately 0.8 mT) which was assigned to the deprotonated guanine radical cation, [G.(-H)] of a DNA subunit. It is assumed that by the UV irradiation the guanine radical cation, (G+.), is generated, either by monophotonic photoionization or by electron transfer to pyrimidine bases. By rapid transfer of the bridging proton from (G+.) to the hydrogen bonded cytosine [G.(-H)] is formed. When photolysis of dsDNA was carried out in the presence of H2O2, reaction of photolytically generated .OH resulted in peroxyl radicals and purine radicals. The oxygen for formation of the peroxyl radicals is probably produced by reaction of [G.(-H)] with H2O2. Photolysis of N2O-saturated solutions containing dsDNA or ssDNA provided another possibility of generation of OH radicals. Under those conditions the .OH-induced radicals (1) and (3) were obtained not only from ssDNA but also from dsDNA.
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:chemical
pubmed:status
MEDLINE
pubmed:issn
8755-0199
pubmed:author
pubmed:issnType
Print
pubmed:volume
11
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
195-206
pubmed:dateRevised
2008-11-21
pubmed:meshHeading
pubmed:year
1990
pubmed:articleTitle
ESR spectra of radicals of single-stranded and double-stranded DNA in aqueous solution. Implications for .OH-induced strand breakage.
pubmed:affiliation
Max-Planck-Institut für Strahlenchemie, Mülheim a.d. Ruhr, FRG.
pubmed:publicationType
Journal Article