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Intramolecular transformation of thiyl radicals to a-aminoalkyl radicals: ab initio calculations on homocystein

Chhun S., Berges J., Bleton V., Abedinzadeh Z.

Nukleonika

2000

Vol. 45, nr 1

19-22

One-electron oxidation of thiols by oxidizing radicals leads to the formation of thiyl and carbon-centered radicals. It has been shown experimentally that in the absence of oxygen, the thiyl radicals derived from certain thiols of biological interest such a glutathione, cysteine and homocysteine decay rapidly by intramolecular rearrangement reactions into the carbon-centered radical. In the present work we have investigated theoretically the structure and the stability of thiyl and carbon-centred radicals of homocystein in order to check the possibility of this rearrangement.

Influence of protonation on the stability of disulfide radicals

Berges J., Fuster F., Silvi B., Jacquot J., Houee-Levin Ch.

Nukleonika

2000

Vol. 45, nr 1

23-29

The ease of disulfide bond cleavage in peptides and proteins is evaluated by an experimental method (one-electron reduction by COOź- radicals and measurement of the chain length) and two theoretical approaches based on quantum chemistry and topology. All results agree to show acidcatalysis of this bond opening. The disulfide bond in the radical state is weakened by protonation.