Research output: Contribution to journal › Article › peer-review
Electron transfer : Vs. proton-coupled electron transfer as the mechanism of reaction between amino acids and triplet-excited benzophenones revealed by time-resolved CIDNP. / Morozova, Olga B.; Panov, Mikhail S.; Fishman, Natalya N. et al.
In: Physical Chemistry Chemical Physics, Vol. 20, No. 32, 15.08.2018, p. 21127-21135.Research output: Contribution to journal › Article › peer-review
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TY - JOUR
T1 - Electron transfer
T2 - Vs. proton-coupled electron transfer as the mechanism of reaction between amino acids and triplet-excited benzophenones revealed by time-resolved CIDNP
AU - Morozova, Olga B.
AU - Panov, Mikhail S.
AU - Fishman, Natalya N.
AU - Yurkovskaya, Alexandra V.
N1 - Publisher Copyright: © 2018 the Owner Societies.
PY - 2018/8/15
Y1 - 2018/8/15
N2 - Hyperfine coupling constants (HFCCs) of the short-lived radicals of 4-carboxy, 4,4′-dicarboxy, and 3,3′,4,4′-tetracarboxy benzophenones (4-CBP, DCBP, and TCBP, respectively) formed in their photoreaction with tyrosine were obtained from analysis of geminate CIDNP spectra. These HFCCs were compared to HFCCs calculated using density functional theory. From this comparison, it was established that the CIDNP pattern of TCBP originates from contributions of three types of TCBP radical structures: the non-protonated anion radical and two anion radical structures with a protonated carboxylic group at position 3 or 4 (or 3′ or 4′). This allowed us to conclude that the mechanism of the quenching reaction is proton coupled electron transfer (PCET): electron transfer is followed by proton transfer to one of four possible positions with similar probabilities. The same CIDNP pattern and therefore the same reaction mechanism was established for histidine. For 4-CBP and DCBP, triplet quenching proceeds also via PCET, again with formation of the anion radical with a protonated carboxylic group.
AB - Hyperfine coupling constants (HFCCs) of the short-lived radicals of 4-carboxy, 4,4′-dicarboxy, and 3,3′,4,4′-tetracarboxy benzophenones (4-CBP, DCBP, and TCBP, respectively) formed in their photoreaction with tyrosine were obtained from analysis of geminate CIDNP spectra. These HFCCs were compared to HFCCs calculated using density functional theory. From this comparison, it was established that the CIDNP pattern of TCBP originates from contributions of three types of TCBP radical structures: the non-protonated anion radical and two anion radical structures with a protonated carboxylic group at position 3 or 4 (or 3′ or 4′). This allowed us to conclude that the mechanism of the quenching reaction is proton coupled electron transfer (PCET): electron transfer is followed by proton transfer to one of four possible positions with similar probabilities. The same CIDNP pattern and therefore the same reaction mechanism was established for histidine. For 4-CBP and DCBP, triplet quenching proceeds also via PCET, again with formation of the anion radical with a protonated carboxylic group.
KW - DYNAMIC NUCLEAR-POLARIZATION
KW - DENSITY-FUNCTIONAL CALCULATIONS
KW - TRYPTOPHAN-TYROSINE PEPTIDE
KW - AQUEOUS-SOLUTION
KW - PHOTO-CIDNP
KW - HISTIDINE
KW - PHOTOOXIDATION
KW - SPECTROSCOPY
KW - REDUCTION
KW - PROTEINS
UR - http://www.scopus.com/inward/record.url?scp=85051942386&partnerID=8YFLogxK
U2 - 10.1039/c8cp03591a
DO - 10.1039/c8cp03591a
M3 - Article
C2 - 30079421
AN - SCOPUS:85051942386
VL - 20
SP - 21127
EP - 21135
JO - Physical Chemistry Chemical Physics
JF - Physical Chemistry Chemical Physics
SN - 1463-9076
IS - 32
ER -
ID: 16104292