engleski

THE INFLUENCE OF AMINO ACID SIDE CHAINS ON WATER BINDING TO THE COPPER(II) IN COPPER(II) COMPLEXES: AN EPR AND A MOLECULAR MECHANICS STUDY

Copper(II) complexes with amino acids and peptides are potentially good models for mimicking enzyme active sites, such as superoxide dismutase. Interactions of amino acid side chains may have important role in this area. To enlarge our knowledge about this kind of compounds, we studied physical and chemical properties of certain copper(II) complexes with amino acids by electron paramagnetic resonance spectroscopy (EPR) and molecular mechanics calculations. Brownian motions of bis(N, N-dimethyl-L- -valinato)copper(II), [Cu(Me2Val)2], and bis(N, N-dimethyl-L- -leucinato)copper(II), [Cu(Me2Leu)2], were studied in different solvents by EPR. WINEPR SimFonia program was used for simulations of spectra at different temperatures. The dependence of reorientation correlation time,   , on viscosity to temperature ratio,  /T, (from Stokes-Einstein relation) can provide useful information about change in conformations of the amino acid side chains in the temperature interval examined. The effective volume of dissolved molecule can also be calculated. The conformational analysis of these compounds has been performed with molecular mechanics force field to find the most stable conformations. The ability of these complexes to bind a water molecule in the copper(II) coordination sphere was examined. The combined EPR and molecular mechanics study has been used to find whether different EPR behaviour of copper(II) complexes could be connected with conformational changes of amino acid side chains.

complexes; amino acids; EPR spectroscopy

nije evidentirano