engleski

Computational study of l-cysteinato-l- asparaginato-copper(II) in gas phase

Copper(II) amino acids complexes compose 5–10% of complexed copper in human blood plasma, competing against the Cu(II)-albumin-bound fraction 1. Cu(II) salts with the deprotonated amino acids histidine (L-His), threonine (L- Thr), asparagine (L-Asn), glutamine (L-Gln), and cysteine (L-Cys) were found to be the most prevalent copper(II) amino acid compounds in human blood serum 1. Due to their small size, the electrically neutral Cu(II)–amino acid complexes can diffuse easily through the biological membranes and participate in copper transport between blood and tissues. The study presented on this poster summarizes results of the conformational analysis of l-cysteinato-l- asparaginato-copper(II) in gas phase. Both cysteine (L-Cys) and asparagine (L-Asn) can donate electrons to copper and hence form coordinative bonds via their different hetero atoms in the main amino acid chain as well as in their side chain, namely sulfur in Cys and nitrogen or oxygen of the amido group in Asn. For this study only the so called glycinato- like mode was chosen, i.e. an approximately planar coordination to copper via amino nitrogen and one carbonyl oxygen from the amino acid main chain (see figure). Other binding modes are still a topic of ongoing research. Starting with this restriction of two five membered chelate rings, three possible torsion angles in both ligands are left to modify and give therefore the number of [2·(3·3·2)^2]=648 input structures. From these, 171 minima were obtained by optimizing the initial structures via DFT/B3LYP calculations with the Gaussian09 program package. The LAN double ζ basis set augmented by polarization and diffuse functions for O, N and C and an effective core potentials for Cu and S were employed. Reference 1. P. Z. Neumann, A. Sass-Kortsak, The State of Copper in Human Serum: Evidence for an Amino Acid- bound Fraction, J Clin Invest 46 (1967) 646 − 658.

copper ; L-cysteine, L-asparagine, conformational analysis ; QM ; DFT/B3LYP ; gas phase

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