Chemically Induced Dynamic Nuclear Polarization (CIDNP) of the diamagnetic products radical reactions is exploited for purpose determination hyperfine coupling constants (HFCCs) intermediates. A simple proportionality relation between geminate CIDNP a nucleus and its HFCC at stage established. The applicability range this determined: fulfilled in case large difference g-factor radicals involved situation where number magnetic nuclei system sufficiently large. validity was confirmed by...

As a model of chemical DNA repair, the reductive electron transfer from aromatic amino acid tyrosine to radical purine base guanosine monophosphate (GMP) was studied by time-resolved chemically induced dynamic nuclear polarization (CIDNP). The guanosyl radicals were photochemically generated in quenching reaction triplet excited dye 2,2'-dipyridyl. Depending on pH aqueous solution, four different observed. identification possible because high sensitivity CIDNP distinguish them through their...

Photo-chemically induced nuclear polarization yields to NMR signal-to-noise enhancement and can be tuned by chemical modification of one the radical-pair partners.

The mechanism of the reactions between photoexcited 2,2'-dipyridyl and N-acetyl tryptophan has been studied by laser flash photolysis time-resolved CIDNP (Chemically Induced Dynamic Nuclear Polarization). transient absorption spectra obtained at different delays after pulse are attributed to triplet state dipyridyl radicals. Depending on pH solution, all three intermediates can be present in either protonated or deprotonated forms. It is shown that irrespective primary photochemical step...

Relative values of the 1H and 13C isotropic hyperfine couplings in cationic oxidized tryptophan radical TrpH*+ aqueous solution are determined. The data obtained from photo-CIDNP (chemically induced dynamic nuclear polarization) enhancements observed microsecond time-resolved NMR spectra diamagnetic products photochemical reactions which is a transient intermediate. method validated using tyrosyl neutral Tyr*, whose have previously been determined by electron paramagnetic resonance...

The reaction mechanism and details of the formation CIDNP (chemically induced dynamic nuclear polarization) in photoreactions 2,2'-dipyridyl (DP) N-acetyl histidine (HisH) aqueous solution have been studied using laser flash photolysis time-resolved techniques. triplet state TDP reacts with protonated HisH2+ via hydrogen atom transfer a rate constant kH = 1.2 × 108 M-1 s-1, deprotonated His- electron ke 7.5 109 s-1. No occurs when imidazole ring is its neutral HisH, or dipyridyl protonated,...

Hyperfine coupling constants (HFCCs) of the short-lived radicals 4-carboxy, 4,4'-dicarboxy, and 3,3',4,4'-tetracarboxy benzophenones (4-CBP, DCBP, TCBP, respectively) formed in their photoreaction with tyrosine were obtained from analysis geminate CIDNP spectra. These HFCCs compared to calculated using density functional theory. From this comparison, it was established that pattern TCBP originates contributions three types radical structures: non-protonated anion two structures a protonated...

Selectively hyperpolarized NMR spectroscopy allows the indirect detection of optically silent methyl histidine radicals in reversible photoinduced reactions dipeptide anserine (β‐alanyl‐1‐methyl‐histidine) with 2,2′‐dipyridyl as photosensitizer using time‐resolved chemically induced dynamic nuclear polarization (TR CIDNP) method. For comparison, experimental data were obtained for 1‐methyl histidine, 3‐methyl and carnosine (β‐alanyl‐histidine). The CIDNP kinetics revealed formation cationic...

Intramolecular electron transfer (IET) from tyrosine to tryptophan cation radicals is investigated using time resolved chemically induced dynamic nuclear polarization (CIDNP) spectroscopy in combination with laser flash photolysis. In both the tryptophan-tyrosine dipeptide and denatured state of hen lysozyme aqueous solution, transformation TrpH+ → TyrO by IET leads an increase radical concentration, growth CIDNP signal, fast decay CIDNP, inversion phase photosensitizing dye, 2,2′-dipyridyl....

The efficiency of the chemical pathway DNA repair is studied by time-resolved chemically induced dynamic nuclear polarization (CIDNP) using model system containing guanosyl base radicals, and tryptophan as electron donor. Radicals were generated photochemically pulsed laser irradiation a solution photosensitizer 2,2'-dipyridyl, guanosine-5'-monophosphate, N-acetyl tryptophan. Depending on pH aqueous solution, four protonation states radical are formed via or hydrogen atom transfer to triplet...

The kinetics of the photooxidation aromatic amino acids histidine (His), tyrosine (Tyr), and tryptophan (Trp) by 3,3',4,4'-benzophenonetetracarboxylic acid (TCBP) has been investigated in aqueous solutions using time-resolved laser flash photolysis chemically induced dynamic nuclear polarization. pH dependence quenching rate constants is measured within a large range. chemical reactivities free His, Trp, Tyr their acetylated derivatives, N-AcHis, N-AcTyr, N-AcTrp, toward TCBP triplets are...

Laser flash photolysis (LFP), low-field chemically induced dynamic nuclear polarization (CIDNP), and time-resolved electron paramagnetic resonance (TREPR) techniques have been used for the comparative study of magnetic field spin effects in acyl−ketyl bis(ketyl)biradicals formed during 2-hydroxy-2,12-dimethylcyclododecanone (1-OH) 2,12-dihydroxy-2,12-dimethylcyclododecanone (2-OH), respectively. The short biradical lifetime, small effect (MFE) on a low intensity spin-correlated radical pair...

The formation of chemically induced dynamic nuclear polarization (1H-CIDNP) and its time evolution in course the photochemical reactions 2,2'-dipyridyl triplet state with tryptophan−tyrosine dipeptide a 1:1 mixture N-acetyl tryptophan tyrosine is studied acid (pH 3.0), neutral 7.4), basic 11.4) solution. Time resolution on microsecond scale allows us to establish full reaction scheme determine all relevant transient intermediates. stationary value spin found depend strongly secondary steps...

Using time-resolved chemically induced dynamic nuclear polarization (CIDNP) techniques, we have studied the mechanism of photoreactions triplet excited 4-carboxybenzophenone (CBP) with l-methionine (Met) and 3-(methylthio)propylamine (MTPA) in aqueous solution details formation CIDNP at pH from 6.7 to 13.6. At a below pKa nitrogen atom Met, is strongly affected by degenerate electron exchange between S−S cationic radical dimer zwitterionic form Met rate constant kex = 3.4 × 108 s-1 providing...

Invisible to other methods, reactions of the histidyl radical could be followed by NMR spectroscopic detection histidine signal through use time-resolved chemically induced dynamic nuclear polarization (CIDNP). CIDNP decay His during photooxidation peptides His-Tyr and Tyr-His pointed electron transfer from tyrosine residue (see scheme for Tyr-His).

Time-resolved chemically induced dynamic nuclear polarization (CIDNP) was used to investigate reversible intramolecular electron transfer (IET) in short-lived oxidized peptides, which had different structures and contained tryptophan tyrosine residues, an acidic aqueous solution with a pH below the pKa of tryptophanyl cation radical. The CIDNP kinetic data were obtained at microsecond scale analyzed detail calculate rate constants for both directions: from residue radical, kf, neutral...

Time-resolved chemically induced dynamic nuclear polarization (CIDNP) and laser flash photolysis (LFP) techniques have been used to study the kinetics mechanism of photochemical reaction between 2,2'-dipyridyl (DP) dipeptide l-tryptophan-l-tyrosine (TrpH-TyrOH) in acidic aqueous solution (pH = 3.8). Analysis geminate CIDNP pattern reveals that quenching protonated triplet dipyridyl TDPH+ results formation both tryptophan tyrosine radicals from with comparative efficiency. The total rate...

An overview of spin hyperpolarisation methods is given; such can be used for strong signal enhancement in nuclear magnetic resonance (NMR). We focus on techniques, which are operative condensed phase and exploit light-induced processes to generate non-thermal hyperpolarisation. Such techniques optical polarisation (ONP), Chemically induced dynamic (CIDNP) pumping (OP). Since all transferred from primarily polarised spins target spins, we also review existing transfer. In the section...

The kinetics of the chemically induced dynamic nuclear polarization (CIDNP) produced in reactions hen lysozyme with photosensitizers have been studied for native state protein at pH 3.8 and two denatured states. latter were generated by raising temperature to 80 °C or combining a rise (to 50 °C) addition chemical denaturant (10 M urea). Detailed analysis CIDNP time dependence on microsecond scale revealed that, both states, intramolecular electron transfer (IET) from tyrosine residue cation...

The photochemical reaction between glycylglycine and triplet 4-carboxybenzophenone has been investigated using time-resolved chemically induced dynamic nuclear polarization (CIDNP). It is shown that the mechanism of peptide with excited carboxybenzophenone electron transfer from amino group peptide, leading to formation an aminium cation radical deprotonates a neutral aminyl radical. Simulation CIDNP kinetics leads estimation paramagnetic relaxation time for alpha-protons at N-terminus 20 40...

Time-resolved chemically induced dynamic nuclear polarization (CIDNP) was applied to the investigation of photo-oxidation two sulfur containing peptides, glycylmethionine (Gly-Met) and methionylglycine (Met-Gly). It established that reaction Gly-Met with a photosensitizer, triplet 4-carboxybenzophenone, occurs via electron transfer from atom also terminal amino group in its uncharged state. The latter process leads formation α-protons glycine residue. sulfur-centered cation radical formed as...