engleski

STRUCTURE PREDICTION OF BIS(AMINO ACIDATO)COPPER(II) COMPLEXES IN DIFFERENT ENVIRONMENTS (VACUUM, CRYSTAL, SOLUTION) WITH THE SAME FORCE FIELD

New molecular mechanics, MM, force field for bis(amino acidato)copper(II) complexes was developed [1]. It is possible to reproduce and predict structural properties of these biologically important low-molecular weight bioinorganic compounds in different environments (in the gas phase and in crystal surroundings by MM simulations, and in aqueous solution by molecular dynamics, MD, calculations) by using the same set of potential energy functions and their carefully selected empirical parameters. The modelling included experimental molecular and crystal structures of 14 anhydrous and 11 aqua copper(II) complexes with aliphatic a-amino acids and their N-alkyl derivatives, with either trans- or cis-N2O2 coordination to the copper(II). During the energy minimization of a crystal, all degrees of freedom (i.e., six lattice constants and 3N position coordinates of the N atoms in the asymmetric unit) were allowed to vary, except a and g unit cell angles, and all three unit cell angles in the cases of a monoclinic and an orthorhombic crystal, respectively. The efficacy of the force field expressed by means of the root-mean-square deviations between the experimental and theoretical crystal values of 25 copper(II) amino acid complexes were as follows: 0.017 &Aring ; ; in the bond lengths, 2.2o in the valence angles, 5.0o in the torsion angles, 0.364 &Aring ; ; in the unit cell lengths. The unit cell volumes were reproduced in the range from – 5.4% to 7.0%. The MD simulations with the new force field were attempted for four solvated bis(glycinato)copper(II) complexes in water. Interesting results were obtained on the complexes’ aggregations dependent on the trans- or cis-coordination of glycine to the copper(II). The new force field proved promising in predicting the association of the complexes in aqueous solution and formation of a nucleus of crystallisation. 1. J. Sabolović, V. Gomzi, J. Chem. Theory Comput. 2009 (accepted for publication)

crystal simulation; MD; MM; copper; amino acids; prediction

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