INTERACTIONS OF MUTAGENS WITH DEOXYRIBONUCLEIC ACIDS
Abstract
The interactions between alkylating agents and deoxyribonucleic acids have been intensively studied in order to provide the molecular basis for the understanding of their carcinogenic and mutagenic properties. The use of direct carbon-13 nuclear magnetic resonance (('13)CNMR) spectroscopy was critically investigated, as a non-destructive method for the analysis of the methylation adducts of DNA. A series of methylated deoxynucleosides were synthesized as model compounds. Salmon sperm DNA and salmon testes DNA were utilized. Methylations were carried out using alkylating agents of different biological potencies. MeMS a weak carcinogen/mutagen and MeNU a potent one. In the methylation of salmon sperm DNA with {('13)C}-MeMS for 6 hours (5% {('14)C}-incorporation) four products were identified: m('1)dA (24.1%), m('7)dG (44.5%), m('3)dC (24.9%) and m('P2) (6.5%). Meanwhile the methylation of salmon testes DNA with {('13)C}-MeMS for 78 hours (5% {('14)C}-incorporation) yielded: m('1)dA (14.2%, m('7)dG (72.1%) and m('3)dC (13.7%). This seems to correlate with the difference in the degree of double strandedness of these two DNA samples. Alkylation of salmon testes DNA with {('13)C}-MeNU for 78 hours (2.6% {('14)-C}-incorporation) yielded: m('1)dA (2.2%), m('7)dG (43.6%), m('3)dC (4.4%), m('3)dT (8.7%), m('4)dT (9.8%), m('P3) (24.0%), m('2)dT (3.2%) and m('6)dG (4.1%). It is important to note that: (1) m('7)dG is the principal product of alkylation of DNA with both alkylating agents, (2) lower formation of m('1)dA and m('3)dC with MeNU, (3) strong methylation at oxygen sites in the reaction of DNA with MeNU and (4) phosphotriesters formation in the reaction of DNA with MeNU not observed in the reaction with MeMS. A more sensitive method was also designed for the study of the methylation of DNA, using RP-HPLC with UV detection following an enzymatic degradation. The qualitative and quantitative results obtained with this technique were in agreement with the results obtained by direct ('13)CNMR spectroscopy.
Degree
Ph.D.
Subject Area
Pharmacology
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