Naslov
Copper(II) amino acid complexes modelled by molecular mechanics method

Autori
Sabolović, Jasmina

Vrsta, podvrsta i kategorija rada
Sažeci sa skupova, sažetak, znanstveni

Izvornik
1999 SFB Congress "Metal Mediated Reactions Modelled After Nature" / - Jena : Friedrich-Schiller-University Jena, 1999, 13-13

Skup
1999 SFB Congress "Metal Mediated Reactions Modelled After Nature"

Mjesto i datum
Jena, Njemačka, 12.09.1999. - 16.09.1999

Vrsta sudjelovanja
Poster

Vrsta recenzije
Međunarodna recenzija

Ključne riječi
molecular mechanics; copper(II); amino acids; X-ray structure; force field

Sažetak
Copper(II) amino acid complexes are normally present in blood plasma or serum, and together with other copper-containing components are thought to constitute the accessible pool of copper for many tissues. Furthermore, copper(II) complexes with amino acids and amino acid derivative ligands are supposed to be good model compounds for the metal-ligand sites at proteins. They are also considered as potentially good models for mimicking the superoxide dismutase activity. So far, their only experimentally available structures have been those determined by X-ray diffraction. In order to predict and simulate properties of both cis and trans tetracoordinated copper(II) amino acid complexes, a molecular mechanics model has been proposed and a new force field derived [1]. Interactions inside a copper(II) coordination polyhedron are modelled with a Morse potential (between the metal and ligand atoms), an electrostatic potential (between four ligand atoms), and a torsion-like potential (with minima at 0 and 180o) that should hold four ligand atoms in a coordination plane. Twelve X-ray crystal structures of anhydrous copper(II) amino acid complexes with the same atom types have been selected for modelling. Eleven are with trans- and one with cis-CuN2O2 coordination polyhedron, with Cu(II) having either an irregular square-planar, a distorted planar or a flattened tetrahedral coordination geometry. The conformational potential energy was minimised for an isolated molecule (in vacuo or a gas phase approximation) as well as for a molecule surrounded with other molecules in a crystal lattice (a condensed phase approximation). The empirical parameters of the selected potential energy functions were optimised with respect to the experimental data (bond lengths, valence and torsion angles, and unit cell dimensions) of five molecules. To assure the planarity of the copper(II) coordination geometry for isolated molecules, the parameters were also optimised with respect to the valence angles around the copper obtained by molecular quantum mechanics for three bis(amino acidato)copper(II) complexes [2]. To test the newly developed force field, the equilibrium geometries of twelve molecules are predicted in vacuo and in approximate crystalline environment. The results were compared with their ab initio and experimental crystal structures, respectively. The unit cell volumes were reproduced in a range from -7.2% to 3.8%. The root-mean-square deviations between the experimental and theoretical crystal structures of 11 trans complexes were 0.018 A in the bond lengths, 2.2o in the valence angles, and 3.9o in the torsion angles (respective rms values for the cis complex were 0.024 A, 2.3o, and 6.3o). The force field is capable of reproducing the differences between the X-ray crystal and ab initio in vacuo structures. 1. B. Kaitner, N. Paulić, G. Pavlović and J. Sabolović, Polyhedron 1999, in press 2. J. Sabolović and K. R. Liedl, Inorg. Chem. 1999, in press

Izvorni jezik
Engleski

Znanstvena područja
Temeljne medicinske znanosti

POVEZANOST RADA