Kinetics of the oxidation of cysteine to cystine by four V(V) oxo diperoxo complexes [VO(O2)2L] possessing insulin mimetic activity, where Lsoxalate(oxa), picolinate (pic), bipyridil (bipy), phenanthroline(phen), were performed in water at 10 8C by the UV or stoppedflow technique. 51V NMR spectra indicate that oxa undergoes a total ligand dissociation differently from pic, bipy and phen which hold their ligands also in solution. The observed reactivity is deeply affected by the identity of the ligand. The process seems to require coordination of the cysteine to the metal, followed by oxidation within the coordination sphere. In this respect phen and bipy make the coordination of cysteine much easier than oxa and pic. It is suggested, also on the basis of some preliminary observations concerning the oxidation of C6H5CH2SH, that the oxidation process is triggered by an electron transfer step. The rate of this step would be higher for oxa and pic than for phen and bipy. The observation that the oxidative ability of these vanadium peroxo complexes is dependent upon the nature of the ligands might match the analogous finding that their insulin mimetic activity is also modulated by the ligand identities. q2000 Elsevier Science Inc. All rights reserved.

Insulinic mimesis of vanadium derivatives. Oxidation of cysteine by V(v) oxo diperoxo complexes

BALLISTRERI, Francesco Paolo;TOSCANO, Rosa Maria
2000

Abstract

Kinetics of the oxidation of cysteine to cystine by four V(V) oxo diperoxo complexes [VO(O2)2L] possessing insulin mimetic activity, where Lsoxalate(oxa), picolinate (pic), bipyridil (bipy), phenanthroline(phen), were performed in water at 10 8C by the UV or stoppedflow technique. 51V NMR spectra indicate that oxa undergoes a total ligand dissociation differently from pic, bipy and phen which hold their ligands also in solution. The observed reactivity is deeply affected by the identity of the ligand. The process seems to require coordination of the cysteine to the metal, followed by oxidation within the coordination sphere. In this respect phen and bipy make the coordination of cysteine much easier than oxa and pic. It is suggested, also on the basis of some preliminary observations concerning the oxidation of C6H5CH2SH, that the oxidation process is triggered by an electron transfer step. The rate of this step would be higher for oxa and pic than for phen and bipy. The observation that the oxidative ability of these vanadium peroxo complexes is dependent upon the nature of the ligands might match the analogous finding that their insulin mimetic activity is also modulated by the ligand identities. q2000 Elsevier Science Inc. All rights reserved.
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Utilizza questo identificativo per citare o creare un link a questo documento: http://hdl.handle.net/20.500.11769/1339
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