TY - JOUR

T1 - Intramolecular Electron Transfer from Tryptophan to Guanosyl Radicals in a Linked System as a Model of DNA Repair

AU - Morozova, Olga B.

AU - Fishman, Natalya N.

AU - Yurkovskaya, Alexandra V.

PY - 2017/3/1

Y1 - 2017/3/1

N2 - As a model of chemical DNA repair, intramolecular electron transfer from tryptophan to the radical of the purine base guanosine combined into a conjugate by a flexible linker was studied by time-resolved chemically induced dynamic nuclear polarization (CIDNP). The guanosyl radicals were photochemically generated in the quenching reaction of the triplet excited dye 2,2′-dipyridyl. The CIDNP kinetics was obtained by detection of NMR spectra containing anomalously enhanced signals of diamagnetic products that are formed during a variable period after excitation by a laser pulse. The kinetic data obtained for the protons located on the guanosyl and tryptophanyl moieties of the conjugate were compared to those obtained in photoreactions of the molecules containing the same linker, but with only one of the two reactive moieties of the conjugate-tryptophanyl or guanosyl. Strong differences between the CIDNP kinetics of different conjugates were revealed and explained by a rapid intramolecular electron transfer from tryptophan to the guanosyl radical in the conjugate. Model simulations of the CIDNP kinetics allowed for determination of the rate constant of intramolecular electron transfer at (1.0±0.5)×106 s-1 indicating a high potential of chemical repair of the guanosyl radical by means of electron transfer from the tryptophanyl moiety in a surrounding protein pool that can provide rather efficient protection of oxidized DNA bases from pathological damage on a submicrosecond time scale.

AB - As a model of chemical DNA repair, intramolecular electron transfer from tryptophan to the radical of the purine base guanosine combined into a conjugate by a flexible linker was studied by time-resolved chemically induced dynamic nuclear polarization (CIDNP). The guanosyl radicals were photochemically generated in the quenching reaction of the triplet excited dye 2,2′-dipyridyl. The CIDNP kinetics was obtained by detection of NMR spectra containing anomalously enhanced signals of diamagnetic products that are formed during a variable period after excitation by a laser pulse. The kinetic data obtained for the protons located on the guanosyl and tryptophanyl moieties of the conjugate were compared to those obtained in photoreactions of the molecules containing the same linker, but with only one of the two reactive moieties of the conjugate-tryptophanyl or guanosyl. Strong differences between the CIDNP kinetics of different conjugates were revealed and explained by a rapid intramolecular electron transfer from tryptophan to the guanosyl radical in the conjugate. Model simulations of the CIDNP kinetics allowed for determination of the rate constant of intramolecular electron transfer at (1.0±0.5)×106 s-1 indicating a high potential of chemical repair of the guanosyl radical by means of electron transfer from the tryptophanyl moiety in a surrounding protein pool that can provide rather efficient protection of oxidized DNA bases from pathological damage on a submicrosecond time scale.

KW - CIDNP

KW - DNA repair

KW - guanosyl radical

KW - magnetic resonance

KW - reaction kinetics

KW - spectroscopy

KW - TIME-RESOLVED CIDNP

KW - AQUEOUS-SOLUTION

KW - GUANYL RADICALS

KW - LASER FLASH-PHOTOLYSIS

KW - TYROSINE

KW - AMINO-ACIDS

KW - PLASMID DNA

KW - GUANINE

KW - PROTON-TRANSFER

KW - CHARGE-TRANSFER

UR - http://www.scopus.com/inward/record.url?scp=85012146280&partnerID=8YFLogxK

U2 - 10.1515/zpch-2016-0784

DO - 10.1515/zpch-2016-0784

M3 - Article

AN - SCOPUS:85012146280

VL - 231

SP - 479

EP - 495

JO - Zeitschrift fur Physikalische Chemie

JF - Zeitschrift fur Physikalische Chemie

SN - 0942-9352

IS - 3

ER -