Anaerobic Oxidation of Cysteine to Cystine by Iron(III). Part 1. The Reaction in Acidic Solution

Article abstract of DOI:10.1039/DT9880000943

The anaerobic oxidation of cysteine (H2L) by iron(III) has been followed in acidic media by use of a stopped-flow high-speed spectrophotometric method.It is suggested that the species responsible is ⁺ which is observable as a transient blue colour on the addition of iron(III) solutions to acidic cysteine solutions.This species exhibits an absorption maximum at 614 nm with a molar absorption coefficient of 1 030 dm³mol^-1cm^-1.The second-order rate constant for its formation from ²⁺ and H2L was found to be 1.14E4 dm³mol^-1s^-1 and the value of log K^{FeOH 2+}> required to fit the data is 2.82.Decomposition to iron(II) and subsequently cystine follows protonation, with an apparent third-order rate constant (including an unknown stability constant) of 1.63E11 dm⁶mol^-2s^-1.All measurements were carried out at 25 deg C in solutions of ionic strength 0.10 mol dm^-3 (KCl).

Full text of DOI:10.1039/DT9880000943

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