Synthetic Analogues for Oxovanadium(IV)–Glutathione Interaction: An EPR, Synthetic and Structural Study of Oxovanadium(IV) Compounds with Sulfhydryl‐Containing Pseudopeptides and Dipeptides

Abstract

(7) was prepared by the reaction of [VOCl 2 (thf) 2 ] with phen in a methanolic solution. The X-ray structure of 3 shows that the vanadium(iv) atom is ligated to a tridentate mpg 3À ligand at the S thiolato , N peptide and O carboxylato atoms. The X-ray structure of 7 is also reported. The optical, infrared, magnetic, electron paramagnetic resonance, and electrochemical properties of compounds 1 ± 5Ć H 3 OH and 7 were studied. Combination of the correlation plots of the EPR parameters g z versus A z , or the groundstate orbital population (b*) 2 versus A z , together with the additivity relationship, A z,calcd Sn i A zi /4, were shown to provide a powerful tool for probing the equatorial donor atoms in an oxovanadium(iv) compound and consequently in biomolecules. Thus, these methods provide valuable evidence for the assignment of the equatorial donor atoms for the V IV O 2 center of the V IV O 2 ± glutathione system at various pH values. Model NMR studies (interaction of vanadium(v) with H 3 mpg) showed that there is a possibility of vanadium(v) ligation to glutathione. The contribution of a deprotonated peptide(amide) nitrogen to A z is not a fixed quantity (it varies from 29 to 43 Â 10 À4 cm À1), but is influenced by the presence of the three other donor atoms in the equatorial plane and, in particular, their charge.

Model studies related to vanadium biochemistry: recent advances and perspectives

“…23 On the other hand, a series of model compounds with sulfhydryl-containing pseudopeptides, and investigated by a combination of numerous physicochemical techniques, also demonstrates the predominance of the cited 2:1 species in the pH range 5-7. 24 The oxidation product of glutathione (GSSG, Figure 2b) can also interact with the VO 2+ cation, and model speciation calculations reveal that in the pH range 6-7, GSSG is a more efficient oxovanadium(IV) binder than GSH. 22 Two different 2:1 complexes, easily interconverted simply by changing the metal-to-ligand concentrations, are generated in the GSSG/VO 2+ system.…”

Vanadium(IV and V) Complexes ContainingSNO (Dithiocarbonylhydrazone; Thiosemicarbazone) Donor Sets

“…Based on the additivity relationship A z ϭ Σn i A zi (n i denotes the nature of the four equatorial ligand functions, and A zi are the corresponding contributions to A z ), [38] a value of 161·10 Ϫ4 cm Ϫ1 is in agreement with an equatorial ClONS donor set in 3a, while a value of 173·10 Ϫ4 cm Ϫ1 should indicate addition of an oxygen-functional ligand L in solution, such as THF, possibly accompanied by a rearrangement of the tridentate ligand so as to place the sulfur donor atom into an axial position.…”

Vanadium (IV and V) Complexes of Reduced Schiff Bases Derived from the Reaction of Aromatic o‐Hydroxyaldehydes and Diamines Containing Carboxyl Groups

“…on their orientation, [28] or the charge of the ligand. [29] The influence of the axial donor groups (if any) is not taken into account.…”