Free radical oxidation of organic disulfides

Bonifacic, M.; Asmus, K.‐D.

doi:10.1021/j100562a021

Cited by 65 publications

(37 citation statements)

References 13 publications

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“…The disul®de bond of the (RSSR À ) radical can be cleaved spontaneously, as shown in (1b), or by protonation, as shown in (1c) (von Sonntag, 1987). Other studies on X-ray irradiation of single crystals of small compounds at 4.2 K (Box et al, 1969) and of hydroxyl radical attack of aqueous solutions at room temperature (Bonifacic & Asmus, 1976) showed the formation of (RSSR + ) radicals as in reactions (1d) and (1e). In the (RSSR + ) radical, a cleavage of the disul®de bond can be initiated by hydroxyl ions (1f; Bonifacic et al, 1975).…”

Section: Introductionmentioning

confidence: 93%

“…Other studies on X-ray irradiation of single crystals of small compounds at 4.2 K (Box et al, 1969) and of hydroxyl radical attack of aqueous solutions at room temperature (Bonifacic & Asmus, 1976) showed the formation of (RSSR + ) radicals as in reactions (1d) and (1e). In the (RSSR + ) radical, a cleavage of the disul®de bond can be initiated by hydroxyl ions (1f; Bonifacic et al, 1975). A cleavage of the disul®de bond can be caused directly by the attack of hydroxyl radicals (1g; Bonifacic et al, 1975).…”

Section: Introductionmentioning

confidence: 93%

“…In the (RSSR + ) radical, a cleavage of the disul®de bond can be initiated by hydroxyl ions (1f; Bonifacic et al, 1975). A cleavage of the disul®de bond can be caused directly by the attack of hydroxyl radicals (1g; Bonifacic et al, 1975).…”

Section: Introductionmentioning

confidence: 99%

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Structural changes in a cryo-cooled protein crystal owing to radiation damage

Burmeister

2000

Acta Crystallogr D Biol Crystallogr

355

387

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The high intensity of third‐generation X‐ray sources, along with the development of cryo‐cooling of protein crystals at temperatures around 100 K, have made it possible to extend the diffraction limit of crystals and to reduce their size. However, even with cryo‐cooled crystals, radiation damage becomes a limiting factor. So far, the radiation damage has manifested itself in the form of a loss of overall diffracted intensity and an increase in the temperature factor. The structure of a protein (myrosinase) after exposure to different doses of X‐rays in the region of 20 × 1015 photons mm−2 has been studied. The changes in the structure owing to radiation damage were analysed using Fourier difference maps and occupancy refinement for the first time. Damage was obvious in the form of breakage of disulfide bonds, decarboxylation of aspartate and glutamate residues, a loss of hydroxyl groups from tyrosine and of the methylthio group of methionine. The susceptibility to radiation damage of individual groups of the same kind varies within the protein. The quality of the model resulting from structure determination might be compromised owing to the presence of radiolysis in the crystal after an excessive radiation dose. Radiation‐induced structural changes may interfere with the interpretation of ligand‐binding studies or MAD data. The experiments reported here suggest that there is an intrinsic limit to the amount of data which can be extracted from a sample of a given size.

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Section: Introductionmentioning

confidence: 93%

Section: Introductionmentioning

confidence: 93%

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Structural changes in a cryo-cooled protein crystal owing to radiation damage

Burmeister

2000

Acta Crystallogr D Biol Crystallogr

355

387

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“…The total measured pH-dependent values are described by the three reactions (9) (10) eaq-+ HSCH2CH2NH3+ -products (11) eaq-+ -SCH2CH2NH,+ -products (12) eaq-+ -SCH,CH,NH, -products (13) and by analogy with eq 8, the general expression for the total measured rate constant is…”

Section: Resultsmentioning

confidence: 99%

Rate constant determination for the reaction of sulfhydryl species with the hydrated electron in aqueous solution

Mezyk¹

1995

J. Phys. Chem.

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The techniques of pulse radiolysis and absorption spectroscopy have been used to determine hydrated electron reaction rate constants with the sulfhydryls mercaptoethanol, 2-aminoethanethiol, cysteine, and penicillamine and the disulfides cystine and penicillamine disulfide, over the pH range 5.0-13.0 in aqueous solution. These values were found to be strongly dependent on the acid-base properties of the sulfhydryl compounds, with the rate constants dependent on the state of protonation of both the amino and mercapto groups, as well as the overall charge in these compounds. Rate constants for reaction of individual sulfhydryl and disulfide species have been determined using literature ionization constants. These values are contrasted to previous literature data.

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“…Extensive studies have revealed, for example, different oxidative properties of sulphur centred radicals and radical ions and it seems that the oxidation potential decreases in the series R 2 St>(R 2 S..SR 2 ) + >(RSSR)t>RS >(RS..SR)- (Asmus 1983). Thus molecular radical cations from sulphides are the most powerful oxidants and readily oxidize disulphides (Bonifacic and Asmus 1976) and thiols (Asmus 1983). The threeelectron bonded complex which is formed by association of R 2 St with an intact sulphide molecule in the equilibrium R 2 St + R 2 S=(R 2 S .. SR 2 ) + (Bonifaci et al 1975 a) generally does not act as an oxidant directly but via equilibration to the more reactive R 2 S t (Bonifacic and Asmus 1976).…”

Section: Introductionmentioning

confidence: 99%

Radical Reactions in Aqueous Disulphide-thiol Systems

Bonifacic¹,

Kd²

1984

International Journal of Radiation Biology and Related Studies

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Absolute rate constants have been measured for the reaction of (CH3SSCH3)+. and sulphur centred radical cations of lipoic acid, lip (SS)+., with various thiols including penicillamine, cysteamine and cysteine. Under pulse radiolysis conditions no reactions was observed between the disulphide radical cations and the neutral thiols, RSH, i.e. kappa less than or equal to 10(7) M-1 s-1. Rate constants in the order of 10(9) M-1 s-1, i.e. close to the diffusion controlled limit, were, however, found for the corresponding reactions with the thiolates, RS-. In systems containing lipoate and cysteamine the lip (S therefore S)+. induced oxidation of CyaS- proceeds via CyaS., (CyaS therefore SCya)- and lip (S S)- as intermediates, i.e. results in a cysteamine mediated conversion of an oxidizing lip (S therefore S)+. radical cation to a reducing lip (S S)- radical anion along the reaction route. In other cases the reaction of disulphide radical cations with thiolate anions was found to proceed via an optically absorbing transient (lambda max approximately 380 nm) which is suggested to be an adduct radical. The mechanism of the (RSSR)+. induced oxidation of thiolate appears to depend on the stability of the 3-electron bonded disulphide radical anion.

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Free radical oxidation of organic disulfides

Cited by 65 publications

References 13 publications

Structural changes in a cryo-cooled protein crystal owing to radiation damage

Structural changes in a cryo-cooled protein crystal owing to radiation damage

Rate constant determination for the reaction of sulfhydryl species with the hydrated electron in aqueous solution

Radical Reactions in Aqueous Disulphide-thiol Systems

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