Photoinduced electron transfer and enhanced triplet yields in benzo[a]pyrene derivative-nucleic acid complexes and covalent adducts

Vladimir Ya Shafirovich, Peter P. Levin, Vladimir A. Kuzmin, Thorgeir E. Thorgeirsson, David S. Kliger, Nicholas Geacintov

Research output: Contribution to journalArticle

Abstract

The carcinogenic and mutagenic benzo[a]pyrenediol epoxide derivative 7r,8t-dihydroxy-9t,10t-epoxy-7,8,9,10-tetrahydrobenzo[a] pyrene (BPDE) binds via its C-10 position predominantly to the exocyclic amino group of guanine residues in native DNA. In such DNA adducts, the fluorescence of the pyrenyl moieties is strongly quenched by physicochemical interaction with the DNA bases. Using nanosecond time scale transient absorption techniques, products of the fluorescence quenching have been examined in two model systems in aqueous and polar organic solvents. The first is a monomeric, covalently linked (+)-trans-BPDE-N2-2'-deoxyguanosine adduct (BPDE-dG), the most abundant adduct when (+)-BPDE binds to native DNA; the second consists of mixtures of 7,8,9,10-tetrahydroxytetrahydrobenzo[a]pyrene (BPT) with dG, which was used to study the role of noncovalent interactions in solvents of different hydrophobicities. At moderate laser pulse energies (≤25 mJ/cm2/pulse, 347 nm), the primary products of the fluorescence quenching reaction are pyrenyl residue triplet excited states, with greatly enhanced yields (by factors of 3-10 or more relative to the yields expected from simple intersystem crossing). The primary quenching reaction involves photoinduced electron transfer from dG to pyrenyl residues, followed by efficient recombination to form triplet excited states. Consistent with this mechanism, pyrenyl radical anions are observed in solutions of BPT and dG (0.1 M) in polar organic solvents. However, radical ions are not observed in any of the covalently linked adducts nor in aqueous solutions of BPT and dG on time scales > 10 ns; triplet excited states are unique products of the fluorescence quenching reaction. These effects are attributed to noncovalent fluorophore-dG interactions in aqueous BPT/dG solutions and to the close proximities of electron donor/acceptor pairs in the covalently linked systems. Both of these circumstances favor rapid ion pair recombination, limiting their escape into the bulk of the solution.

Original languageEnglish (US)
Pages (from-to)63-72
Number of pages10
JournalJournal of the American Chemical Society
Volume116
Issue number1
StatePublished - Jan 12 1994

Fingerprint

Benzo(a)pyrene
7,8-Dihydro-7,8-dihydroxybenzo(a)pyrene 9,10-oxide
Nucleic acids
Pyrene
Nucleic Acids
Quenching
Fluorescence
Excited states
Electrons
Derivatives
DNA
Organic solvents
Genetic Recombination
Laser pulses
Ions
Deoxyguanosine
DNA Adducts
Fluorophores
Epoxy Compounds
Guanine

ASJC Scopus subject areas

  • Chemistry(all)

Cite this

Photoinduced electron transfer and enhanced triplet yields in benzo[a]pyrene derivative-nucleic acid complexes and covalent adducts. / Shafirovich, Vladimir Ya; Levin, Peter P.; Kuzmin, Vladimir A.; Thorgeirsson, Thorgeir E.; Kliger, David S.; Geacintov, Nicholas.

In: Journal of the American Chemical Society, Vol. 116, No. 1, 12.01.1994, p. 63-72.

Research output: Contribution to journalArticle

Shafirovich, Vladimir Ya ; Levin, Peter P. ; Kuzmin, Vladimir A. ; Thorgeirsson, Thorgeir E. ; Kliger, David S. ; Geacintov, Nicholas. / Photoinduced electron transfer and enhanced triplet yields in benzo[a]pyrene derivative-nucleic acid complexes and covalent adducts. In: Journal of the American Chemical Society. 1994 ; Vol. 116, No. 1. pp. 63-72.
@article{30d35439132e493288f00016edd554bf,
title = "Photoinduced electron transfer and enhanced triplet yields in benzo[a]pyrene derivative-nucleic acid complexes and covalent adducts",
abstract = "The carcinogenic and mutagenic benzo[a]pyrenediol epoxide derivative 7r,8t-dihydroxy-9t,10t-epoxy-7,8,9,10-tetrahydrobenzo[a] pyrene (BPDE) binds via its C-10 position predominantly to the exocyclic amino group of guanine residues in native DNA. In such DNA adducts, the fluorescence of the pyrenyl moieties is strongly quenched by physicochemical interaction with the DNA bases. Using nanosecond time scale transient absorption techniques, products of the fluorescence quenching have been examined in two model systems in aqueous and polar organic solvents. The first is a monomeric, covalently linked (+)-trans-BPDE-N2-2'-deoxyguanosine adduct (BPDE-dG), the most abundant adduct when (+)-BPDE binds to native DNA; the second consists of mixtures of 7,8,9,10-tetrahydroxytetrahydrobenzo[a]pyrene (BPT) with dG, which was used to study the role of noncovalent interactions in solvents of different hydrophobicities. At moderate laser pulse energies (≤25 mJ/cm2/pulse, 347 nm), the primary products of the fluorescence quenching reaction are pyrenyl residue triplet excited states, with greatly enhanced yields (by factors of 3-10 or more relative to the yields expected from simple intersystem crossing). The primary quenching reaction involves photoinduced electron transfer from dG to pyrenyl residues, followed by efficient recombination to form triplet excited states. Consistent with this mechanism, pyrenyl radical anions are observed in solutions of BPT and dG (0.1 M) in polar organic solvents. However, radical ions are not observed in any of the covalently linked adducts nor in aqueous solutions of BPT and dG on time scales > 10 ns; triplet excited states are unique products of the fluorescence quenching reaction. These effects are attributed to noncovalent fluorophore-dG interactions in aqueous BPT/dG solutions and to the close proximities of electron donor/acceptor pairs in the covalently linked systems. Both of these circumstances favor rapid ion pair recombination, limiting their escape into the bulk of the solution.",
author = "Shafirovich, {Vladimir Ya} and Levin, {Peter P.} and Kuzmin, {Vladimir A.} and Thorgeirsson, {Thorgeir E.} and Kliger, {David S.} and Nicholas Geacintov",
year = "1994",
month = "1",
day = "12",
language = "English (US)",
volume = "116",
pages = "63--72",
journal = "Journal of the American Chemical Society",
issn = "0002-7863",
publisher = "American Chemical Society",
number = "1",

}

TY - JOUR

T1 - Photoinduced electron transfer and enhanced triplet yields in benzo[a]pyrene derivative-nucleic acid complexes and covalent adducts

AU - Shafirovich, Vladimir Ya

AU - Levin, Peter P.

AU - Kuzmin, Vladimir A.

AU - Thorgeirsson, Thorgeir E.

AU - Kliger, David S.

AU - Geacintov, Nicholas

PY - 1994/1/12

Y1 - 1994/1/12

N2 - The carcinogenic and mutagenic benzo[a]pyrenediol epoxide derivative 7r,8t-dihydroxy-9t,10t-epoxy-7,8,9,10-tetrahydrobenzo[a] pyrene (BPDE) binds via its C-10 position predominantly to the exocyclic amino group of guanine residues in native DNA. In such DNA adducts, the fluorescence of the pyrenyl moieties is strongly quenched by physicochemical interaction with the DNA bases. Using nanosecond time scale transient absorption techniques, products of the fluorescence quenching have been examined in two model systems in aqueous and polar organic solvents. The first is a monomeric, covalently linked (+)-trans-BPDE-N2-2'-deoxyguanosine adduct (BPDE-dG), the most abundant adduct when (+)-BPDE binds to native DNA; the second consists of mixtures of 7,8,9,10-tetrahydroxytetrahydrobenzo[a]pyrene (BPT) with dG, which was used to study the role of noncovalent interactions in solvents of different hydrophobicities. At moderate laser pulse energies (≤25 mJ/cm2/pulse, 347 nm), the primary products of the fluorescence quenching reaction are pyrenyl residue triplet excited states, with greatly enhanced yields (by factors of 3-10 or more relative to the yields expected from simple intersystem crossing). The primary quenching reaction involves photoinduced electron transfer from dG to pyrenyl residues, followed by efficient recombination to form triplet excited states. Consistent with this mechanism, pyrenyl radical anions are observed in solutions of BPT and dG (0.1 M) in polar organic solvents. However, radical ions are not observed in any of the covalently linked adducts nor in aqueous solutions of BPT and dG on time scales > 10 ns; triplet excited states are unique products of the fluorescence quenching reaction. These effects are attributed to noncovalent fluorophore-dG interactions in aqueous BPT/dG solutions and to the close proximities of electron donor/acceptor pairs in the covalently linked systems. Both of these circumstances favor rapid ion pair recombination, limiting their escape into the bulk of the solution.

AB - The carcinogenic and mutagenic benzo[a]pyrenediol epoxide derivative 7r,8t-dihydroxy-9t,10t-epoxy-7,8,9,10-tetrahydrobenzo[a] pyrene (BPDE) binds via its C-10 position predominantly to the exocyclic amino group of guanine residues in native DNA. In such DNA adducts, the fluorescence of the pyrenyl moieties is strongly quenched by physicochemical interaction with the DNA bases. Using nanosecond time scale transient absorption techniques, products of the fluorescence quenching have been examined in two model systems in aqueous and polar organic solvents. The first is a monomeric, covalently linked (+)-trans-BPDE-N2-2'-deoxyguanosine adduct (BPDE-dG), the most abundant adduct when (+)-BPDE binds to native DNA; the second consists of mixtures of 7,8,9,10-tetrahydroxytetrahydrobenzo[a]pyrene (BPT) with dG, which was used to study the role of noncovalent interactions in solvents of different hydrophobicities. At moderate laser pulse energies (≤25 mJ/cm2/pulse, 347 nm), the primary products of the fluorescence quenching reaction are pyrenyl residue triplet excited states, with greatly enhanced yields (by factors of 3-10 or more relative to the yields expected from simple intersystem crossing). The primary quenching reaction involves photoinduced electron transfer from dG to pyrenyl residues, followed by efficient recombination to form triplet excited states. Consistent with this mechanism, pyrenyl radical anions are observed in solutions of BPT and dG (0.1 M) in polar organic solvents. However, radical ions are not observed in any of the covalently linked adducts nor in aqueous solutions of BPT and dG on time scales > 10 ns; triplet excited states are unique products of the fluorescence quenching reaction. These effects are attributed to noncovalent fluorophore-dG interactions in aqueous BPT/dG solutions and to the close proximities of electron donor/acceptor pairs in the covalently linked systems. Both of these circumstances favor rapid ion pair recombination, limiting their escape into the bulk of the solution.

UR - http://www.scopus.com/inward/record.url?scp=0028213690&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=0028213690&partnerID=8YFLogxK

M3 - Article

AN - SCOPUS:0028213690

VL - 116

SP - 63

EP - 72

JO - Journal of the American Chemical Society

JF - Journal of the American Chemical Society

SN - 0002-7863

IS - 1

ER -