Combination of equilibrium dialysis, melting behaviour and circular dichroism spectroscopy in the study of genotoxic chemicals using ethylene oxide as a model substance.
Ethylene oxide was incubated with different homobasic polynucleotides or dinucleotides. These were subsequently hybridized in equilibrium dialysis with their complementary or noncomplementary counterparts and the equilibrium constants determined. A change of the equilibrium constants after reaction with ethylene oxide corresponded with a shift in melting temperature of the reacted and hybridized macromolecular polynucleotides. The melting temperature was also changed when calf thymus DNA was reacted with ethylene oxide. In addition, the effect of ethylene oxide on the macromolecular single-stranded and double-stranded nucleic acids was investigated by studying the difference in rotation of circularly polarized light with the technique of circular dichroism spectroscopy. The changes in the spectra showed that ethylene oxide had altered the conformation of the hybridized double strands. These data indicated that binding sites in the pyrimidine bases of nucleic acid molecules, besides the previously known N-7 position in the purine base guanine, are attacked by ethylene oxide. There is evidence for the generation of N(4)-(2-hydroxyethyl)cytosine, O(2)-(2-hydroxyethyl)thymine and O(4)-(2-hydroxyethyl)uracil when the corresponding pyrimidine polynucleotides are incubated with ethylene oxide.
Marczynski
B
B
Berufsgenossenschaftliches Forschungsinstitut für Arbeitsmedizin an der Ruhr-Universität Bochum, Gilsingstrasse 14, D-4630 Bochum, Germany.
Foest
U
U
Hallier
E
E
Snatzke
G
G
Hegemann
J
J
Peter
H
H