Kinetic Evidence for Transiently Shifted Acidity Constant of Histidine Linked to Paramagnetic Tyrosine Probed by Intramolecular Electron Transfer in Oxidized Peptides

2021 ◽  
Author(s):  
Olga B. Morozova ◽  
Dmitri Stass ◽  
Alexandra V. Yurkovskaya
Keyword(s):  
Electron Transfer ◽  
Dynamic Nuclear Polarization ◽  
Nuclear Polarization ◽  
Intramolecular Electron Transfer ◽  
Acidity Constant ◽  
Time Resolved ◽  
Chemically Induced ◽  
Kinetics Of

Kinetics of electron transfer (ET) from tyrosine (Tyr) to short-lived histidine (His) radicals in peptides of different structures was monitored using time-resolved chemically induced dynamic nuclear polarization (CIDNP) to follow...

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

2017 ◽  
Vol 231 (3) ◽  
Author(s):  
Olga B. Morozova ◽  
Natalya N. Fishman ◽  
Alexandra V. Yurkovskaya
Keyword(s):  
Electron Transfer ◽  
Dna Repair ◽  
Kinetic Data ◽  
Nuclear Polarization ◽  
Intramolecular Electron Transfer ◽  
Time Resolved ◽  
Purine Base ◽  
Chemically Induced ◽  
Kinetics Of

AbstractAs 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)×10

scholarly journals Electron self-exchange activation parameters of diethyl sulfide and tetrahydrothiophene

2013 ◽  
Vol 9 ◽  
pp. 1448-1454
Author(s):  
Martin Goez ◽  
Martin Vogtherr
Keyword(s):  
Electron Transfer ◽  
Photoinduced Electron Transfer ◽  
Nuclear Polarization ◽  
Activation Barrier ◽  
Activation Parameters ◽  
Radical Cations ◽  
Free Energies ◽  
Time Resolved ◽  
Diethyl Sulfide ◽  
Chemically Induced

Electron transfer between the title compounds and their radical cations, which were generated by photoinduced electron transfer from the sulfides to excited 2,4,6-triphenylpyrylium cations, was investigated by time-resolved measurements of chemically induced dynamic nuclear polarization (CIDNP) in acetonitrile. The strongly negative activation entropies provide evidence for an associative–dissociative electron exchange involving dimeric radical cations. Despite this mechanistic complication, the free energies of activation were found to be well reproduced by the Marcus theory of electron transfer, with the activation barrier still dominated by solvent reorganization.

Competition of singlet and triplet recombination of radical pairs in photoreactions of carboxy benzophenones and aromatic amino acids

2019 ◽  
Vol 21 (4) ◽  
pp. 2017-2028 ◽  
Author(s):  
Olga B. Morozova ◽  
Peter S. Sherin ◽  
Alexandra V. Yurkovskaya
Keyword(s):  
Amino Acids ◽  
Dynamic Nuclear Polarization ◽  
Nuclear Polarization ◽  
Transient Absorption ◽  
Branching Ratio ◽  
Aromatic Amino Acids ◽  
Radical Pairs ◽  
Time Resolved ◽  
Chemically Induced

Time-resolved chemically induced dynamic nuclear polarization and transient absorption were applied to reveal the branching ratio of the singlet and triplet recombination channels in the reaction of short-lived radicals of carboxy benzophenones and the aromatic amino acids.

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