2-mm band EPR spectroscopy of semiquinone radicals in rigid media

Gulin, V. I.; Samoilova, Rimma I.; Dikanov, Sergei A.; Tsvetkov, Yu. D.

doi:10.1007/bf03166053

Cited by 7 publications

(6 citation statements)

References 9 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The spin density dist¡ in mm is very sensitive in quinones both to the strucmre of the quinone and to protonation of the oxygens. In this respect, the g-factors reflect the unpaired spin density at the carbonyl groups and should be as characteristic of a given species as the proton hyperfine which reflects the unpaired spin density on the carbon adjacent to the proton [16]. In both cases, identification of a particular radical species relies on the sensitivity of the unpaired spin density distribution to the structure of the radical and on the precision to which the hyperfine coupling or g-factor can be measured.…”

Section: Introductionmentioning

confidence: 99%

Characterization of free radicals from vitamin K1 and menadione by 2 mm-band EPR, ENDOR and ESEEM

et al. 1992

Self Cite

View full text Add to dashboard Cite

The anion and cation radicals of vitamin K 1 and its analog menadione were characterized using the magnetic resonance techniques of Electron Nuclear Double Resonance (ENDOR), Electron Spin Echo Envelope Modulation (ESEEM), and Electron Paramagnetic Resonance (EPR) at X-band and 2 mm-band. The g-factor anisotropy of the radicals at 2 mmband allow them to be distinguished from each other in the solid state. The g-factor matrix of the radical anion of vitamin K~ is virtually identicat with that reported for the reduced A~ acceptor in green plant photosystem I thus demonstrating that reduced A~ is the anion radical of vitamin K 1.

show abstract

Section: Introductionmentioning

confidence: 99%

Characterization of free radicals from vitamin K1 and menadione by 2 mm-band EPR, ENDOR and ESEEM

et al. 1992

Self Cite

View full text Add to dashboard Cite

show abstract

“…Yet, the identification of distinct carbohydrate conformations requires combining complementary techniques. These techniques vary from other experimental methods to atomistic molecular dynamics simulations [46,64,[80][81][82].…”

Section: Structural Characterization Of Polysacchridesmentioning

confidence: 99%

“…Classical molecular dynamics (MD) simulations can be used to complement incomplete experimental data and to provide detailed conformational distributions in time and space that experimental measurements can only obtain as averages [80,82,83]. It can also be used to predict properties under environmental conditions that may not be accessible to experimental measurements.…”

Section: Structural Characterization Of Polysacchridesmentioning

confidence: 99%

“…In addition, quantum-mechanical data is not an ideal validation target as it only yields gasphase quantities. Model validation and comparisons of biomolecular simulations are often best done against condensed-phase experimental data [82,98,101]. The availability of structural data on carbohydrates has made possible the creation of several databases like the SUGABASE, CarbBank, EUROCarbDB, Glycoconjugate DB, GLYCOSCIENCES.de, GlycoSuiteDB, JCGGDB, KEGG-Glycan, CFG-Glycan Database and GlycoBase.…”

Section: Structural Characterization Of Polysacchridesmentioning

confidence: 99%

See 1 more Smart Citation

The Molecular Structure and Conformational Dynamics of Chitosan Polymers: An Integrated Perspective from Experiments and Computational Simulations

Cunha¹,

Soares²,

Rusu³

et al. 2012

The Complex World of Polysaccharides

View full text Add to dashboard Cite

“…Moreover, the reaction can be straightforwardly controlled, by switching on and off the light pulses. The feasibility investigation is performed for the reduction of benzoquinone − and 2,6-dichlorophenolindophenol (DCPIP) , by ascorbate (vitamin C) as important representatives for two-step redox reactions, whereby paramagnetic one-electron oxidized and reduced intermediates are investigated by electron paramagnetic resonance (EPR) spectroscopy.…”

Section: Introductionmentioning

confidence: 99%

Reversed Freeze Quench Method near the Solvent Phase Transition

Marchanka

Gastel

2012

J. Phys. Chem. A

View full text Add to dashboard Cite

Freeze quenching is a general method for trapping reaction intermediates on a (sub)millisecond time scale. The method relies on a mixing and subsequent rapid freezing of solutions of reactants. If the reaction is limited by diffusion, it may be advantageous to initially mix the reactants under conditions where the reaction does not proceed, e.g., by mixing them at low temperature as solids. The temperature may then be raised close to the melting point of the solvent. Depending on the viscosity of the solvent, the temperature can be raised either by heating or by applying laser pulses of nanosecond length with concomitant conversion of light into heat. A reduction of the dead time and a good control of the reaction speed in comparison to the standard freeze quench technique has been achieved with this method. The feasibility of the method in combination with EPR spectroscopy is verified by examining the important prototypical reductions of benzoquinone and 2,6-dichlorophenolindophenol by ascorbate as representatives for two-step redox reactions. By using light pulses of a laser, the reaction could be driven with rates lowered by 4 orders of magnitude as compared to room temperature reaction rates. This has allowed the observation of previously unobserved radical intermediates: the reduction of DCPIP by ascorbate is found to be strongly pH dependent. It proceeds via two one-electron steps at low pH, whereas at neutral pH, the reduction of DCPIP by ascorbate proceeds in a 1:2 stoichiometry followed by a disproportionation of the ascorbate radicals.

show abstract

2-mm band EPR spectroscopy of semiquinone radicals in rigid media

Cited by 7 publications

References 9 publications

Characterization of free radicals from vitamin K1 and menadione by 2 mm-band EPR, ENDOR and ESEEM

Characterization of free radicals from vitamin K1 and menadione by 2 mm-band EPR, ENDOR and ESEEM

The Molecular Structure and Conformational Dynamics of Chitosan Polymers: An Integrated Perspective from Experiments and Computational Simulations

Reversed Freeze Quench Method near the Solvent Phase Transition

Contact Info

Product

Resources

About