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Title: Physico-chemical methods for the study of polycyclic aromatic hydrocarbon - DNA interactions. Progress report, October 1, 1985-September 30, 1986

Abstract

Previous linear dichroism measurements suggested that the (-)BPDE-DNA adducts are characterized by considerable interactions between the pyrene residue and the DNA bases. Such a conformation is consistent with intercalation, or partial intercalation. With the pyrene residue thus protected from the solvent environment, one might expect a low degree of accessibility to acrylamide quencher molecules. Since the fluorescence of these (-)BPDE-DNA adducts is indeed insensitive to acrylamide, the quenching results reported here are consistent with such a conformation. The covalent adducts derived from the binding of (+)BPDE to DNA appear to be 70% accessible to acrylamide, suggesting that a majority of these adducts reside at external binding sites, or in a locally disordered region of the DNA double helix. Again, these conclusions derived from the fluorescence quenching data are consistent with our previous linear dichroism results. 3 refs., 3 figs.

Authors:
Publication Date:
Research Org.:
New York Univ., NY (USA). Dept. of Chemistry
OSTI Identifier:
5000033
Report Number(s):
DOE/EV/04959-8
ON: DE87000957
DOE Contract Number:
AC02-78EV04959
Resource Type:
Technical Report
Country of Publication:
United States
Language:
English
Subject:
63 RADIATION, THERMAL, AND OTHER ENVIRON. POLLUTANT EFFECTS ON LIVING ORGS. AND BIOL. MAT.; 59 BASIC BIOLOGICAL SCIENCES; DNA ADDUCTS; FLUORESCENCE SPECTROSCOPY; ACRYLAMIDE; BENZOPYRENE; DICHROISM; MOLECULAR MODELS; SYNCHROTRON RADIATION; ADDUCTS; AMIDES; AROMATICS; BREMSSTRAHLUNG; CONDENSED AROMATICS; ELECTROMAGNETIC RADIATION; EMISSION SPECTROSCOPY; HYDROCARBONS; MATHEMATICAL MODELS; ORGANIC COMPOUNDS; ORGANIC NITROGEN COMPOUNDS; RADIATIONS; SPECTROSCOPY; 560300* - Chemicals Metabolism & Toxicology; 550200 - Biochemistry

Citation Formats

Geacintov, N.E. Physico-chemical methods for the study of polycyclic aromatic hydrocarbon - DNA interactions. Progress report, October 1, 1985-September 30, 1986. United States: N. p., 1986. Web.
Geacintov, N.E. Physico-chemical methods for the study of polycyclic aromatic hydrocarbon - DNA interactions. Progress report, October 1, 1985-September 30, 1986. United States.
Geacintov, N.E. 1986. "Physico-chemical methods for the study of polycyclic aromatic hydrocarbon - DNA interactions. Progress report, October 1, 1985-September 30, 1986". United States. doi:.
@article{osti_5000033,
title = {Physico-chemical methods for the study of polycyclic aromatic hydrocarbon - DNA interactions. Progress report, October 1, 1985-September 30, 1986},
author = {Geacintov, N.E.},
abstractNote = {Previous linear dichroism measurements suggested that the (-)BPDE-DNA adducts are characterized by considerable interactions between the pyrene residue and the DNA bases. Such a conformation is consistent with intercalation, or partial intercalation. With the pyrene residue thus protected from the solvent environment, one might expect a low degree of accessibility to acrylamide quencher molecules. Since the fluorescence of these (-)BPDE-DNA adducts is indeed insensitive to acrylamide, the quenching results reported here are consistent with such a conformation. The covalent adducts derived from the binding of (+)BPDE to DNA appear to be 70% accessible to acrylamide, suggesting that a majority of these adducts reside at external binding sites, or in a locally disordered region of the DNA double helix. Again, these conclusions derived from the fluorescence quenching data are consistent with our previous linear dichroism results. 3 refs., 3 figs.},
doi = {},
journal = {},
number = ,
volume = ,
place = {United States},
year = 1986,
month =
}

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  • Research completed over the past three years is summarized. Topics discussed include: triplet probe methods for studying the micro-confirmations of aromatic molecules bound to DNA; electric linear dichroism studies of conformations of adducts derived from the binding of structurally related PAH epoxide model compounds to DNA; mechanisms of reaction of PAH diol epoxides in aqueous solutions containing DNA; stereoselective binding of enantiomers of BaPDE with DNA; development of a new flow dichroism technique to monitor changes in the orientations of carcinogens at DNA binding sites as they undergo reactions with nucleic acids; and the binding of anti-BaPDE to a typicalmore » carrier protein (serum albumin). 3 figures.« less
  • Linear dichroism was used to study the conformations of polycyclic aromatic carcinogen-DNA adducts and non-covalent complexes, as well as for following the kinetics of the interactions of the highly reactive metabolites of these carcinogens with DNA in aqueous solutions. We have also begun to investigate the fluorescence properties of carcinogen-DNA adducts. The results of these studies on the base-sequence selectivities and base-sequence specificities of the interactions of polycyclic aromatic hydrocarbon diol epoxides with nucleic acids, have stimulated the developments of models of reaction mechanisms and biological activity/carcinogen-DNA adduct structure relationships. 18 refs., 4 figs., 1 tab.
  • The goal of this project was to develop new spectroscopic techniques and to adapt existing methods for studies of the interactions of polycyclic aromatic mutagens and carcinogens with nucleic acids. A highly sensitive, computer-interfaced linear dichroism system was constructed to allow for studies of the conformations of carcinogen-DNA non-covalent complexes and covalent adducts. Fluorescence techniques were adapted for studies of the heterogeneities of carcinogen-DNA adducts utilizing fluorescence emission spectra, and detailed comparisons between excitation and absorption spectra acquired with digital instrumentation. Detailed fluorescence quenching studies, together with accurate determinations of fluorescence decay profiles utilizing the National Synchrotron Light Source atmore » the Brookhaven National Laboratory, allowed for a determination of the solvent exposure of the polycyclic aromatic moieties in covalent carcinogen-DNA adducts. Finally, a detailed study of the base-sequence dependence of non-covalent intercalation complex formation and chemical reactivity of poycyclic aromatic diol epoxide with synthetic polynucleotides was performed. These studies provided insight into the detailed mechanisms of interaction of benzo(a)pyrene trans-7,8-dihydrodiol-9,10-epoxide with DNA. 19 refs., 4 figs., 1 tab.« less
  • By studying the reaction rate, intercalative noncovalent binding, and covalent binding of benzo(a)pyrene-7,8-diol-9,10-oxide to different synthetic polynucleotides, a deeper understanding of the reaction mechanisms of aromatic diol epoxide carcinogens with DNA has been obtained. Studies on the structures of the covalent adducts provide a good model for the mechanisms of interaction of these carcinogenic and tumorigenic molecules with DNA. 5 refs., 3 figs.
  • Polycyclic aromatic hydrocarbon (PAH) constitute a well-known class of environmental carcinogens and mutagens, and occur in coal, coal tars and in combustion products of coal-fired plants. In living cells these PAH molecules are metabolized to a variety of oxygenated derivatives. Some of these metabolites, the epoxides and diol epoxides, are chemically very reactive and form chemical adducts with nucleic acids. It is widely believed that the formation of these carcinogen-DNA adducts is the critical step which transforms a normal cell into a pre-cancerous state. In this work, the reaction mechanisms of benzo(a)pyrene diol epoxide (BPDE) with DNA and the structuremore » of the covalent adducts formed have been studied in detail under controlled laboratory conditions in aqueous solutions. When two solutions, one containing BPDE and the other DNA, are mixed rapidly (approx. 5 ms) in a stopped-flow apparatus, a non-covalent BPDE-DNA intercalation complex is formed. The preferred reaction pathway of the diol epoxide at this intercalation site is the nucleophilic addition of water to form the corresponding tetraol, while only 5 to 10% of the BPDE molecules present bind covalently to tthe nucleic acid bases. The DNA-catalyzed hydrolysis of the diol epoxide appears to prevent more extensive covalent adduct formation. The conformation of the covalent BPDE-DNA adduct is quite different from the non-covalent BPDE intercalation complex. In the covalent adduct the pyrenyl moeity appears to be located at an accessible exterior DNA binding site. Analagous experiments with a benzo(a)pyrene epoxide (similar in structure to BPDE but lacking the two OH groups) show that there are at least two different types of binding sites one of which appears to be an exterior site, while the other resembles an intercalation binding site.« less