TY - JOUR
T1 - Model studies of DNA photorepair
T2 - Reduction potentials of thymine and cytosine cyclobutane dimers measured by fluorescence quenching
AU - Scannell, Michael P.
AU - Fenick, David J.
AU - Yeh, Syun Ru
AU - Falvey, Daniel E.
PY - 1997/2/26
Y1 - 1997/2/26
N2 - The interactions of various pyrimidines (1,3-dimethylthymine, DMT, 1,3-bis(N4,N4-dimethylcytosin-1-yl)propane, DMC) and their corresponding cis-syn cyclobutane dimers (DMTD and DMCD) with a series of excited-state electron donors were examined with the goal of understanding the energetics and mechanism of UV repair by DNA photolyase. For each substrate there is a good correlation between the excited state oxidation potential (E(ox)*) and the quenching rate constant (k(q)). The value for k(q) increases as E(ox)* becomes more negative, asymptotically approaching a value that is at or below the solvent diffusion limit. These data all showed good fits to the Rehm-Weller equation. Reduction potentials for each of the substrates could be extracted from this analysis: -2.20 V (vs SCE) for DMTD; -2.14 V for DMT; -2.17 V for DMCD; and -2.16 for DMC. These values show that the initial electron transfer step in the photolyase mechanism is exergonic by ca. 10-15 kcal/mol. Thus these data support the reductive electron transfer mechanism for DNA photolyases proposed by Jorus et al.
AB - The interactions of various pyrimidines (1,3-dimethylthymine, DMT, 1,3-bis(N4,N4-dimethylcytosin-1-yl)propane, DMC) and their corresponding cis-syn cyclobutane dimers (DMTD and DMCD) with a series of excited-state electron donors were examined with the goal of understanding the energetics and mechanism of UV repair by DNA photolyase. For each substrate there is a good correlation between the excited state oxidation potential (E(ox)*) and the quenching rate constant (k(q)). The value for k(q) increases as E(ox)* becomes more negative, asymptotically approaching a value that is at or below the solvent diffusion limit. These data all showed good fits to the Rehm-Weller equation. Reduction potentials for each of the substrates could be extracted from this analysis: -2.20 V (vs SCE) for DMTD; -2.14 V for DMT; -2.17 V for DMCD; and -2.16 for DMC. These values show that the initial electron transfer step in the photolyase mechanism is exergonic by ca. 10-15 kcal/mol. Thus these data support the reductive electron transfer mechanism for DNA photolyases proposed by Jorus et al.
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U2 - 10.1021/ja963360o
DO - 10.1021/ja963360o
M3 - Article
AN - SCOPUS:0030887103
SN - 0002-7863
VL - 119
SP - 1971
EP - 1977
JO - Journal of the American Chemical Society
JF - Journal of the American Chemical Society
IS - 8
ER -