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Speciation studies of Co(II), Ni(II) and Cu(II) complexes of L-valine in acetonitrile-water mixtures

Posted on 20. December, 2013.

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Speciation study of essential metal ion complexes with amino acids is useful to understand the role played by the active site cavities in biological molecules and the bonding behaviour of protein residues with the metal ion. Chemical speciation of a molecule is governed by its structure and solvent effects. Hence, in recent years, researchers have shown interest in the study of metal ions interaction with various ligands

Valine is an essential branched-chain amino acid, the lack of which may influence the growth of body, cause neuropathic obstacle and anemia. Binary stability constants of L-valine with Co(II), Ni(II) and Cu(II) have been reported using batch equilibrium method with cation exchange resin (Hirano and Koyanagi, 1981), and potentiometric (Albert, 1950) and pH-metric (Rengaraj et al., 1991) titration methods. SCOGS (Hallman et al., 1971), CHEMEQ (Nooshafarin and Charles, 2005) and SUPERQUAD (Khatoon and Kabi-ud-Din, 1989) computer programs were used to evaluate the stability constants.

Binary complexes of norvaline, an isomer of L-valine, with Co(II) and Cu(II) have been reported using paper electrophoretic (Tewari, 2010) and ionophoretic (Tewari, 2008) technique. Acetonitrile, a colourless polar aprotic, behaves as a weaker base (Laubengayer and Sears, 1945) and as a much weaker acid (Fritz and Yamamura, 1955) than water. Acetonitrile also acts as a strongly differentiating solvent with a modest solvating power for many polar ionic solutes (Aktas et al., 2006). Co(II), Ni(II) and Cu(II) are associated with several enzymes and any variation in their concentrations leads to metabolic disorders (Kolodziej, 1994). Hence, the speciation of Co(II), Ni(II) and Cu(II) complexes of L-valine in varying compositions of acetonitrile–water mixtures have been studied.

To read the complete article in Chemical Speciation & Bioavailability, click here.

doi: 10.3184/095422913X13838472787746

Photo: Speculative structures of L-valine complexes, where S is either solvent or water molecule.

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