Muon Spectroscopy Applied to Biological Systems: A Study of Thiyl Radicals, RS

Rhodes, Christopher J.; Hinds, Chantal S.; Morris, Harry; Reid, I. D.

doi:10.3109/10715769709065773

Cited by 6 publications

(4 citation statements)

References 10 publications

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“…4 The muon coupling constants corresponding to these (but actually obtained by the transverse field µSR technique) are shown (in their reduced form A′ µ ) in the rightmost column of Table 1, denoted d). It is worthy of note that they are in each case smaller than those measured by Rhodes et al, 11 probably indicating that the radicals are fairly strongly dipolar and interact considerably with water. The calculated values of A(X) for all nuclei X showing substantial couplings in adducts of III and IV are presented in Table 2, together with the experimental values for A( 1 H) and A( 14 N).…”

Section: Resultsmentioning

confidence: 55%

“… a Values lacking temperature-dependences are from ref ; the others are from ref . Couplings are in MHz and gradients are in MHz/K.…”

Section: Resultsmentioning

confidence: 99%

“…This is thought to be a result of the near-degeneracy of the π x and π y levels inherited from the prototype sulfanyl radical SH (see, for example, ref ) and which leads to the Jahn−Teller distortion in CH 3 S • ; , dynamical averaging of a highly anisotropic g -tensor leads to extremely broad spectra. Variants of the muon spin rotation (μSR) technique, in which the place of atomic hydrogen is taken by its light isotope muonium, have however detected radicals formed by addition to CS in liquids, ,,− and from general considerations such as the assumption (supported by semiempirical calculations) that the C adduct is more stable and the rather large size of the hyperfine coupling as compared to couplings obtained in carbonyl systems (hundreds rather than tens of MHz) the observed signals have been almost globally assigned to S-centered thiyl radicals from Mu addition at C. The one exception is the adduct radical to (Ph) 2 CS, where the low muon coupling (equivalent to A p ∼ 21.7 MHz at 298 K 2 ) is taken as evidence that addition in this case is to S, with a case being reasoned out for this conclusion in terms of electronic inductive effects.…”

Section: Introductionmentioning

confidence: 99%

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Density Functional Studies of Hydrogen Atom Addition to the CS Bond

Macrae¹,

Carmichael²

2001

J. Phys. Chem. A

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The results of density functional theory calculations on the structures, energetics, and hyperfine properties of radical H adducts to the C and S atoms of several thioketones and related species are presented. Despite the greater thermochemical stability of the C adduct in several cases, the isotropic proton couplings (and, where data are available, 14 N couplings) make it clear that the species observed in µSR experiments are S adducts, counter to the assignments made by the experimentalists. The preference for S addition is probably a result of the barrier associated with the geometrical distortion required for addition at C or may indicate a formation mechanism involving a charged intermediate. The distribution of the magnitudes of the couplings of both C and S adducts shows that previous intuitive arguments are inadequate in the assignment of experimental data. Calculation of the dynamically averaged temperature-dependent coupling within a one-mode approximation corrected for zero-point bond stretching yields almost-quantitative agreement with experiment for thioacetamide assuming addition is to S.

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Section: Resultsmentioning

confidence: 55%

“… a Values lacking temperature-dependences are from ref ; the others are from ref . Couplings are in MHz and gradients are in MHz/K.…”

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Density Functional Studies of Hydrogen Atom Addition to the CS Bond

Macrae¹,

Carmichael²

2001

J. Phys. Chem. A

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“…for thiyl radicals, which are highly reactive, especially in non-polar media 9 . Oxidation of thiols, present in cells to defend against reactive radicals, often results in the formation of thiyl radicals, which although generally undetectable in solution by ESR, directly 109 may be spin-trapped. A novel phosphorylated spin-trap, 5-diethoxyphosphoryl-5-methyl-1-pyrroline-N-oxide, which may be considered an analogue of DMPO, has been used to investigate the reactions of sulfur centred radicals produced by the oxidation of thiols with peroxynitrite 110 .…”

Section: Thiyl Radicals In Lipid Peroxidationmentioning

confidence: 99%

Electron Spin Resonance.: Part One: A Diagnostic Method in the Biomedical Sciences

Rhodes

2011

Science Progress

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A review is presented of some of the ways in which electron spin resonance (ESR) spectroscopy may be useful to investigate systems of relevance to the biomedical sciences. Specifically considered are: spin-trapping in biological media; the determination of antioxidant efficiencies; lipid-peroxidation; the use of nitroxides as probes of metabolic activity in cells and as structural probes of cell-membranes; ESR coupled with materials for radiation-dosimetry; foodand drug-irradiation; studies of enzyme systems and of cyclodextrins; diagnosis of cancer and rheumatoid arthritis; measurement of oxidative stress in synovial tissue in preparation for joint replacement; determination of oxidative species during kidney dialysis; measurement of biological oxygen concentrations (oximetry); trapping in living cells of the endothelium-derived relaxing factor nitric oxide (NO); measurement of hydrogen peroxide; determination of drugs of abuse (opiates); ESR measurements of whole blood and as a means to determine the age of bloodstains for forensic analysis are surveyed, and also a determination of the aqueous volume of human sperm cells is described, among other topics.

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Radiolabelling studies of free radical reactions using muonium (the second hydrogen radioisotope): evidence of a direct antioxidant role for vitamin k in repair of oxidative damage to lipids

et al. 2000

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Following the recent suggestion that oxidative damage to lipids might involve the formation of C‐2 glyceryl radicals, in addition to main‐chain allylic radicals, which are generally thought important, we studied the kinetics of potential ‘repair’ reactions by vitamin E and vitamin K1 (which are lipophilic and tend to locate in cell membranes) with 1,1,2‐trimethylallyl and 1‐acetoxyprop‐2‐yl radicals as models of, respectively, main‐chain and glyceryl‐type radicals. The second‐order rate constants for the reaction between trimethylallyl radicals and vitamin E and vitamin K1 are 9.38 × 106 and 3.54 × 108 l mol−1 s−1 and those between 1‐acetoxyprop‐2‐yl radicals and vitamin E and vitamin K1 are 1.76 × 108 and 2.03 × 106 l mol−1 s−1, respectively. The results suggest that direct scavenging of glyceryl radicals by vitamin E should be an efficient process, and of main‐chain allylic radicals fairly so. Additionally, it appears that vitamin K1 can act directly as a ‘radical repair agent,’ given its relatively high reactivity with allylic radicals (four times faster than with vitamin E), so prior reduction to the quinol form may be unnecessary. Copyright © 2000 John Wiley & Sons, Ltd.

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Muon Spectroscopy Applied to Biological Systems: A Study of Thiyl Radicals, RS

Cited by 6 publications

References 10 publications

Density Functional Studies of Hydrogen Atom Addition to the CS Bond

Density Functional Studies of Hydrogen Atom Addition to the CS Bond

Electron Spin Resonance.: Part One: A Diagnostic Method in the Biomedical Sciences

Radiolabelling studies of free radical reactions using muonium (the second hydrogen radioisotope): evidence of a direct antioxidant role for vitamin k in repair of oxidative damage to lipids

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