Kinetics of Reversible Protonation of Transient Neutral Guanine Radical in Neutral Aqueous Solution

Morozova, Olga B.; Fishman, Natalya N.; Yurkovskaya, Alexandra V.

doi:10.1002/cphc.201800539

Cited by 9 publications

(6 citation statements)

References 44 publications

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“…The standard electrode potential of GMP at pH = 7, E 7 = 1.31 V [ 64 ], determined from photoinduced electron transfer reaction rates, agrees well with that of guanosine at pH = 7, E 7 = 1.29 V [ 65 ], determined by pulsed radiolysis. The acidity constants of GMP [ 66 ] and its radical [ 67 , 68 , 69 ] are shown in Scheme 3 . For GMP(-H) • /GMP(-H) − , the calculated potential is E 0 = 1.23 V.…”

Section: Resultsmentioning

confidence: 99%

Marcus Cross-Relationship Probed by Time-Resolved CIDNP

Geniman,

Morozova,

Lukzen

et al. 2023

IJMS

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The time-resolved CIDNP method can provide information about degenerate exchange reactions (DEEs) involving short-lived radicals. In the temperature range from 8 to 65 °C, the DEE reactions of the guanosine-5′-monophosphate anion GMP(-H)− with the neutral radical GMP(-H)•, of the N-acetyl tyrosine anion N-AcTyrO− with a neutral radical N-AcTyrO•, and of the tyrosine anion TyrO− with a neutral radical TyrO• were studied. In all the studied cases, the radicals were formed in the reaction of quenching triplet 2,2′-dipyridyl. The reorganization energies were obtained from Arrhenius plots. The rate constant of the reductive electron transfer reaction in the pair GMP(-H)•/TyrO− was determined at T = 25 °C. Rate constants of the GMP(-H)• radical reduction reactions with TyrO− and N-AcTyrO− anions calculated by the Marcus cross-relation differ from the experimental ones by two orders of magnitude. The rate constants of several other electron transfer reactions involving GMP(-H)−/GMP(-H)•, N-AcTyrO−/N-AcTyrO•, and TyrO−/TyrO• pairs calculated by cross-relation agree well with the experimental values. The rate of nuclear paramagnetic relaxation was found for the 3,5 and β-protons of TyrO• and N-AcTyrO•, the 8-proton of GMP(-H)•, and the 3,4-protons of DPH• at each temperature. In all cases, the dependences of the rate of nuclear paramagnetic relaxation on temperature are described by the Arrhenius dependence.

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Section: Resultsmentioning

confidence: 99%

Marcus Cross-Relationship Probed by Time-Resolved CIDNP

Geniman,

Morozova,

Lukzen

et al. 2023

IJMS

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“…The reason is that in the case of the neutral GMP radical the

Δ g

‐value has the sign opposite to that in the case of the dication and anion GMP radicals. Such a sign change is unambiguously determined by CIDNP …”

Section: Cidnp Studies Of Fast Reactions Of Radicalsmentioning

confidence: 99%

“…Such a sign change is unambiguously determined by CIDNP. [68] In the second example, see Figure 11b, we present a CIDNP study of radicals of the Met-Gly and Gly-Met peptides. [50a] In this case different structures of the radicals are expected for Met-Gly and Gly-Met: in the former case a cyclic radical with a twocenter three-electron bond is formed, while in the latter case linear S-centered or N-centered radicals are formed.…”

Section: Cidnp Studies Of Fast Reactions Of Radicalsmentioning

confidence: 99%

“…Hence, a quantitative analysis of HFC constants inevitably requires using time-resolved CIDNP. 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 An example [69] illustrating the proportionality relation between HFC constants and CIDNP intensities is given in Figure 12 for benzophenone (BP) used as a dye and Tyr used as a quencher. In this case, an RP comprising the radicals with the HFC constants known from EPR, [70] namely the BP and Tyr radicals, was used.…”

Section: Cidnp Studies Of Fast Reactions Of Radicalsmentioning

confidence: 99%

“…This method has been applied to a variety of radicals in room-temperature aqueous solutions. [56,69] When different reaction mechanisms result in the formation of radical structures with different HFC values, the analysis of geminate CIDNP signal intensities allows one to discriminate between different reaction pathways, for example, such as sequential or concerted electron transfer and proton transfer processes from phenol moieties to triplet excited benzophenones. [71] By analyzing the CIDNP kinetics one can study fast reactions of radicals.…”

Section: Cidnp Studies Of Fast Reactions Of Radicalsmentioning

confidence: 99%

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Time‐Resolved Chemically Induced Dynamic Nuclear Polarization of Biologically Important Molecules

Morozova

Ivanov

2018

ChemPhysChem

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In this work, we review the hyperpolarization technique named chemically induced dynamic nuclear polarization (CIDNP), focusing on the time‐resolved variant of this method and its biological applications. We introduce the main principles of polarization formation in liquids at high magnetic fields, provided by the so‐called spin sorting mechanism. Applications of CIDNP to studying fast reactions of short‐lived free radicals of biologically important molecules are discussed, as well as the potential of the method to probe the structure and magnetic parameters of such radicals. We also explain the principles of protein CIDNP and discuss applications of time‐resolved CIDNP to studies of protein structure and dynamics.

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Chemically Induced Spin Hyperpolarization: Coherence Formation in Reaction Products

et al. 2021

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Chemically induced dynamic nuclear polarization (CIDNP) has emerged as a highly informative method to study spin-dependent radical reactions by analyzing enhanced NMR (nuclear magnetic resonance) signals of their diamagnetic reaction products. In this way, one can probe the structure of elusive radical intermediates and determine their magnetic parameters. A careful examination of experimental CIDNP data at variable magnetic fields shows that formation of hyperpolarized molecules in a coherent state is a ubiquitous though rarely discussed phenomenon. The presence of nuclear spin coherences commonly leads to subsequent polarization transfer among coupled spins in the diamagnetic products of radical recombination reaction that must be taken into account when analyzing the results of CIDNP experiments at low magnetic field. Moreover, such coherent polarization transfer can be efficiently exploited to polarize spins, which do not acquire CIDNP directly. Here we explain under what conditions such coherences can be generated, focusing on the key role of level anti-crossings in coherent polarization transfer, and provide experimental approaches to probing nuclear spin coherences and their time evolution. We illustrate the theoretical consideration of the outlined coherent spin phenomena in CIDNP by examples, obtained for the dipeptide tryptophan–tryptophan.

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Kinetics of Reversible Protonation of Transient Neutral Guanine Radical in Neutral Aqueous Solution

Cited by 9 publications

References 44 publications

Marcus Cross-Relationship Probed by Time-Resolved CIDNP

Marcus Cross-Relationship Probed by Time-Resolved CIDNP

Time‐Resolved Chemically Induced Dynamic Nuclear Polarization of Biologically Important Molecules

Chemically Induced Spin Hyperpolarization: Coherence Formation in Reaction Products

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