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In this work the binding of V^IVO²⁺ and V^IVO-complexes to serum albumins {human serum albumin (HSA), bovine serum albumin (BSA) and porcine serum albumin (PSA)} are studied using circular dichroism (CD), electron paramagnetic resonance (EPR) and visible absorption spectroscopy. The results confirm previous findings that V^IVO²⁺ occupies at least two types of binding sites on albumin: ‘the strong vanadium binding site’ (designated by VBS1) and ‘the weak vanadium binding sites’ (designated by VBS2). VBS1 binds 1 mol equivalent of V^IVO²⁺. On the other hand VBS2 correspond to binding of several mol equivalents of V^IVO, and studies done with PSA in the presence of excess Zn^II ions indicate that VSB2 corresponds to two distinct types of sites. The hyperfine coupling constant A_z for V^IVO²⁺ binding at VBS2 on HSA and BSA are all very similar (~168 × 10-4 cm^-1) but differ slightly on PSA (~166 × 10-4 cm^-1) due to differences in the binding sets. When (V^IVO)-HSA systems are titrated with maltol ternary species of (maltol)_m(V^IVO)_mHSA and (maltol)_2m(V^IVO)_mHSA stoichiometry form which are clearly distinguishable from the binary (V^IVO)-HSA system by the type and intensity of the CD spectra recorded. Changes are also observable in the intensity of the X-band EPR spectra, but not much in the hyperfine coupling constants A_z, which are all in the range 166-167 × 10-4 cm^-1. The results further demonstrate that the presence of maltol may enhance the binding of VIVO to albumin.

The pyrimidinones mhcpe, 2-methyl-3H-5-hydroxy-6-carboxy-4-pyrimidinone ethyl ester (mhcpe, 1), 2,3-dimethyl-5-benzyloxy-6-carboxy-4-pyrimidinone ethyl ester (dbcpe, 2) and N-methyl-2,3-dimethyl-5-hydroxy-6-carboxyamido-4-pyrimidinone (N-MeHOPY, 3), are synthesized and their structures determined by single crystal X-ray diffraction. The acid-base properties of 1 are studied by potentiometric and spectrophotometric methods, the pK a values being 1.14 and 6.35. DFT calculations were carried out to determine the most stable structure for each of the H 2 L + , HL and L − forms (HL = mhcpe) and assign the groups involved in the protonation-deprotonation processes. The mhcpe − ligand forms stable complexes with V IV O 2+ in the pH range 2 to 10, and potentiometry, EPR and UV-Vis techniques are used to identify and characterize the V IV O-mhcpe species formed. The results are consistent with the formation of V IV O,