ISBN: 978-83-60043-10-3 - eurobic9

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Eurobic9, 2-6 September, 2008, Wrocław, Poland P81. Fe L-edge XAS Determination of Differential Orbital Covalency of Siderophore Model Compounds: Electronic Structure Contributions to High Stability Constants R.K. Hocking a, b , J. Xu c , E. Dertz c , S. DeBeer George d , K.N. Raymond c , K.O. Hodgson d , B. Hedman d a, d and E.I. Solomon a Department of Chemistry, Stanford University, Stanford, California 94305, USA b Monash Centre for Synchrotron Science and School of Chemistry, Monash University. 3800, Australia c Department of Chemistry, University of California, Berkeley, USA d Stanford Synchrotron Radiation Laboratory, SLAC, Stanford University, Stanford California, 94309, USA Many micro-organisms produce low-molecular weight iron-chelators called siderophores. Although many different siderophore structures have been characterised, the iron bonding moieties generally contain carboxylate, hydroxamate, or catecholate binding groups. Siderophores function because of their extraordinarily high stability constants. Recently we have developed a methodology that enables the interpretation of Fe L-edges in terms of differential orbital covalency (i.e. the differences in the mixing of the metal d orbitals with ligand valence orbitals) using a valence bond configuration interaction model. We have now applied this methodology to a series of model siderophores understand the electronic structure contributions to these stability constants in terms of σ and π covalent as well as ionic contributions to bonding. Acknowledgement: This work was in part performed at SSRL, which is funded by the DOE Office of Basic Energy Sciences. The SSRL Structural Molecular Biology Program is supported by the NIH National Center for Research Resources, Biomedical Technology Program and by the DOE Office of Biological and Environmental Research. _____________________________________________________________________ 200
Eurobic9, 2-6 September, 2008, Wrocław, Poland P82. Coordination abilities of alloferon peptides towards copper ions A. Janicka-Kłos a , A. Bonna b , A. Prahl c , H. Kozłowski d , J. Świątek-Kozłowska a a Department of Inorganic Chemistry, Faculty of Pharmacy Silesian Piast University of Medicine in Wroclaw, Szewska 38, 50-139 Wroclaw, Poland e-mail: anna_janicka@yahoo.pl b Department of Biophysics, Institute of Biochemistry and Biophysics Polish Academy of Sciences, Pawinskiego 5a, 02-<strong>10</strong>6 Warszawa, Poland c Department of Organic Synthesis, Faculty of Chemistry, University of Gdansk, Sobieskiego 18/19, 80-952 Gdansk, Poland d Faculty of Chemistry, University of Wroclaw, F. Joliot-Curie 14, 50-3<strong>83</strong> Wroclaw, Poland Two peptides isolated from bacteria-challenged larvae of the blow fly Calliphora vicina: HGVSGHGQHGVHG (alloferon 1) and GVSGHGQHGVHG (alloferon 2) posses potent antiviral and antitumoral activity [1]. Both peptides are rich in histidine and thus are supposed to be able to effectively bind Cu 2+ ions. It is proved that copper is required by several key proteins involved in the stimulation of angiogenesis as it acts as an important cofactor for their angiogenic activity [2]. Several reports show that reduction of copper level at tumor sites interrupts angiogenesis what results in prevention of tumor growth and its metastasis. An essential step in tumor proliferation, expansion and metastasis is angiogenesis. It is believed that a switch of angiogenic phenotype in a tissue is dependent upon the local balance between angiogenic factors and inhibitors. It is also speculated that most endogenous angiogenesis inhibitors in a vascular tissues are protein molecules and their fragments [1, 3, 4]. The aim of this work was to experimentally check coordination abilities of both alloferon peptides towards copper ions. Potentiometric and spectroscopic techniques (CD, UV-Vis and EPR) were performed and provide evidence of Cu 2+ /peptide complexes. At the physiological pH (pH 7-8) three species with different protonation state are present in equilibrium where metal ion is bound via the imidazole nitrogen of His and amide nitrogens. References: [1] S. Chernysh, S. I. Kim, G. Bekker, V. A. Pleskach, N. A. Filatova, V. B. Anilin, V. G. Platonov, P. Bulet, PNAS, 99, 12628, (2002) [2] S. Brem, Cancer Control, 6, 436, (1999) [3] M.A. Moses, R. Langer, J. Cell. Biochem., 47, 230, (1991) [4] V. L. Goodman, G. J. Brewer, S. D. Merajver, Endocrine-Related Cancer, 11, 255, (2004) _____________________________________________________________________ 201
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Author Index Eurobic9, 2-6 Septembe
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ISBN: 978-83-60043-10-3 - eurobic9

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