The Analysis of Cu(II)/Zn(II) Cyclopeptide System as Potential Cu,ZnSOD Mimic Center.

In this paper are presented the features of copper (II) and zinc (II) heteronuclear complexes of the cyclic peptide-c(HKHGPG)2. The coordination properties of ligand were studied by potentiometric, UV-Vis and CD spectroscopic methods. These experiments were carried out in aqueous solutions at 298 K depending on pH. It turned out that in a physiological pH dominates Cu(II)/Zn(II) complex ([CuZnL]4+) which could mimic the active center of superoxide dismutase (Cu,ZnSOD). In next step we performed in vitro research on Cu,ZnSOD activity for [CuZnL]4+ complex existing in 7.4 pH by the method of reduction of nitroblue tetrazolium (NBT). Also mono- and di-nuclear copper (II) complexes of this ligand were examined. The ability of inhibition free radical reaction were compared for all complexes. The results of these studies show that Cu(II) mono-, di-nuclear and Cu(II)/Zn(II) complexes becoming to new promising synthetic superoxide dismutase mimetics, and should be considered for further biological assays.

The coordination abilities of the multiHis-cyclopeptide with two metal-binding centers--potentiometric and spectroscopic investigation.

In this paper we present the formation of mono- and binuclear complexes by the octapeptide (c(HKHPHKHP)) with copper(II) ions. The ligand was synthesized manually by the solid-phase method. Its characteristic cyclic structure significantly influences the coordination abilities. The studied peptide has two Pro amino acid residues in the sequence. This causes the formation of two independent centres able to undertake metal ion binding. The potentiometric and spectroscopic (UV-vis, CD and EPR) studies were carried out in aqueous solutions in the pH range 2.5-11.0 at 298 K, HNO(3) was used as the solvent with KNO(3), where the ionic strength was 0.1 M. The analysis of the potentiometric together with spectroscopic studies have shown that the investigated peptide forms only mono-nuclear complexes when the metal-to-ligand molar ratio is 1 : 1. When the concentration of Cu(ii) ions increases and the ligand-to-metal molar ratio is 1 : 2 the formation of binuclear complexes is preferred in the system.

Molecular determinants of the interaction between human high molecular weight kininogen and Candida albicans cell wall: Identification of kininogen-binding proteins on fungal cell wall and mapping the cell wall-binding regions on kininogen molecule.

An excessive production of vasoactive and proinflammatory bradykinin-related peptides, the kinins, is often involved in the human host defense against microbial infections. Recent studies have shown that a major fungal pathogen to humans, Candida albicans, can bind the proteinaceous kinin precursor, the high molecular weight kininogen (HK) and trigger the kinin-forming cascade on the cell surface. In this work, we preliminarily characterized a molecular mechanism underlying the HK adhesion to the fungal surface by (i) identification of major kininogen-binding constituents on the candidial cell wall and (ii) mapping the cell wall-binding regions on HK molecule. A major fraction of total fungal kininogen-binding capacity was assigned to ß-1,3-glucanase-extractable cell wall proteins (CWP). By adsorption of CWP on HK-coupled agarose gel and mass spectrometric analysis of the eluted material, major putative HK receptors were identified, including Als3 adhesin and three glycolytic enzymes, i.e., enolase 1, phosphoglycerate mutase 1 and triosephosphate isomerase 1. Using monoclonal antibodies directed against selected parts of HK molecule and synthetic peptides with sequences matching selected HK fragments, we assigned the major fungal cell wall-binding ability to a short stretch of amino acids in the C-terminal part of domain 3 and a large continuous region involving the C-terminal part of domain 5 and N-terminal part of domain 6 (residues 479-564). The latter characteristics of HK binding to C. albicans surface differ from those reported for bacteria and host cells.

Colorimetric evaluation of the time-killing assay for Citropin 1.1, lipopeptide Palm-KK-NH2, and Temporin A.

Nowadays, there are a number of colorimetric techniques available for the determination of a time killing assay in a manner much easier and faster than those previously more commonly used, which were much more time-consuming and laborious colony counting procedures. Here, an attempt has been made to test the antimicrobial peptides of Citropin 1.1, Palm-KK-NH2, and Temporin A on a reference strain of Staphylococcus aureus using resazurin as the cell viability reagent. Staphylococcus aureus was exposed to the test compounds over varying periods of time and the metabolic activity measured, with a profile of antimicrobial activity then established. The results are in agreement with data from previous literature, thus confirming the relevance of the application of resazurin for the testing of antimicrobial agents.

The -Cys-Cys- motif in Helicobacter pylori's Hpn and HspA proteins is an essential anchoring site for metal ions.

The Hpn and HspA proteins from H. pylori are significant for nickel homeostasis and protect the cells from higher concentrations of external metal ions. Both proteins have a unique histidine- and cysteine-rich domain at the C terminus. The interactions of Ni(2+), Bi(3+), Zn(2+) and Cd(2+) ions with C-terminal Ac-CCSTSDSHHQ-NH(2) and Ac-EEGCCHGHHE-NH(2) fragments from Hpn and the Ac-GSCCHTGNHD-NH(2) sequence from HspA were studied by potentiometry, mass spectrometry, circular dichroism and UV-Vis spectroscopy. Ac-CC-NH(2) was used as a reference peptide. The studies have shown that nickel ions form planar complexes with a {2S(-),N(-)} binding mode. The thiol sulfurs of the -Cys-Cys- motif are also the anchoring sites for Bi(3+), Zn(2+) and Cd(2+) ions. The studied protein fragments have the highest affinity for Bi(3+) ions. The thermodynamic stability of Ni(2+) is much higher then that of Zn(2+).

Camelina sativa cake improved unsaturated fatty acids in ewe's milk.

BACKGROUND: Camelina sativa cake (CSC), a rich source of unsaturated fatty acids, in the case of ruminants, may improve the energy value of a diet and also increase the unsaturated fatty acid content in milk. Effects of basal diet (control), basal diet plus 30 g kg(-1) of CSC in dietary dry matter (DM), basal diet plus 60 g kg(-1) of CSC in dietary dry matter on milk production and the fatty acid composition of ewe's milk with particular emphasis on the monoenes and conjugated isomers of linoleic acid content were examined. RESULTS: Elevated concentration of total monounsaturated fatty acids, the effect of an increase in monounsaturated fatty acids in the trans configuration, as well as the increased content of total polyunsaturated fatty acids, resulted from CSC supplementation. Total saturated fatty acid concentration was decreased. CONCLUSION: Milk from CSC-supplemented ewes was characterized by increased levels of beneficial nutritional factors, including mono- and n-3 polyunsaturated fatty acids, and was also by lower atherogenic and thrombogenic indices. Taking into consideration all the obtained results and recommended fat concentrations in a daily ruminant ration, we recommend supplementing a dairy ewe's diet with 30 g kg(-1) DM of CSC cake in practice.

Synthesis, biological activity and solution structure of new analogues of the antimicrobial Gramicidin S.

Gramicidin S (GS) is a cyclo-decapeptide antibiotic isolated from Bacillus brevis. The structural studies have shown that GS forms a two-stranded antiparallel ß-sheet imposed by two II' ß-turns. Despite its wide Gram+ and Gram- antimicrobial spectrum, GS is useless in therapy because of its high hemotoxicity in humans. It was found, however, that the analogues of GS-14 (GS with 14 amino acid residues) attained a better antimicrobial selectivity when their amphipatic moments were perturbed. In this study, we report effects of similar perturbations imposed on GS cyclo-decapeptide analogues. Having solved their structures by NMR/molecular dynamics and having tested their activities/selectivities, we have concluded that the idea of perturbation of the amphipatic moment does not work for GS-10_0 analogues. An innovative approach to the synthesis of head-to-tail cyclopeptides was used.

Cu2+ and Ni2+ interactions with N-terminal fragments of Hpn and Hpn-like proteins from Helicobacter pylori: unusual impact of poly-Gln sequence on the complex stability.

The N-terminal protected and unprotected peptides MAHHEEQHG-NH(2), Ac-MAHHEEQHG-NH(2) from Hpn (Helicobacter histidine-rich protein) and MAHHEQQQQQQA-NH(2), Ac-MAHHEQQQQQQA-NH(2) from Hpn-like protein, respectively, were synthesized and their interactions with Cu(2+) and Ni(2+) ions were studied by potentiometric, UV-visible, CD, and EPR techniques. The studies have shown that because of their albumin-like sequence, unprotected peptides are very effective chelating agents for both studied metals. The presence of the hexa-glutamine sequence has very distinct impact on the stability of the complexes formed even if direct interactions with metal ions were not found. The much more effective Ni(2+) binding by Hpn-like N-terminal domain when compared to Hpn protein could be critical for different biological functions played by both proteins.

The cyclopeptides with the multi-His motif as ligands for copper(II).

The coordination properties of cyclic octapeptides with multi-His motif: c(His-Gly-His-Xaa-His-Gly-His-Xaa) where Xaa = Asp or Lys, were investigated. The binding abilities of this peptides towards Cu(II) ions were studied by using different analytic methods as: potentiometry, spectroscopy and mass spectrometry. The obtained results show that the studied peptides in physiological related pH prefer formation of the species with the {4N(Im)} binding mode. The efficiency of Cu(II) binding depends on additional side chain groups Asp or Lys. Additionally the analysis of results for His containing cyclopeptides with different numbers of amino acid residues in cyclopeptide ring e.g. four, eight shows that in higher pH in both cases the binding by four amide nitrogens is not observed in the case of α-amino acid peptides.