1,721,050 research outputs found
Competition between histamine-like and poly-imidazole coordination sites for Cu2+ and Zn2+ ions in zebra-fish peptide of prion-like protein
No full textThe fragment of the zebrafish prion-like protein (PrP-rel-2), encompassing residues 74-86 and unprotected at N-terminus (zf74-86) represents a good model to understand Cu2+ and Zn2+ binding to
ligands containing multi-potential metal donor sites. Zf(74-86) contains four His and His-1 N-terminal amine groups which constitute both copper and zinc anchoring sites. The presence of His at the first
position additionally provides the histamine-like binding mode which could compete with the multi-His binding mode. In this study the speciation profiles of the Cu2+ and Zn2+ complexes with zf74-86 have
been obtained. The main species, dominating at physiological pH, have been fully characterized by using different spectroscopic techniques. The detected NMR chemical shift variations and line broadening enhancements, caused by Zn2+ and Cu2+ respectively, allowed to determine the metal binding sites. Both metal ions showed common binding donor atoms, being 2 or 3 His imidazoles and the N-terminal group involved in Cu2+ and Zn2+ binding
Binding of Ni2+ and Cu2+ ions to peptides with a Cys-His motif
No full textWaglerin I is a 22 amino acid snake venom toxin. Its three fragments (GGKPDLRPCHP-NH2,
PCHYIPRPKPR-NH2, PCHPPCHYIPR-NH2), due to the presence of two Cys and His residues, are
potentially very attractive ligands for transition metal ions. The main aim of this work was to establish
the impact of these two adjacent residues on Ni2+ ion binding, especially because this kind of motif is
very common in nature, and the study of low molecular weight models could be helpful in
understanding larger systems. In this work waglerin fragments and their N-protected analogues were
studied with Ni2+ (and Cu2+ for peptides with disulfide bridges) ions using combined potentiometric
and spectroscopic measurements (UV-Vis, CD, EPR and NMR). In all peptides, except
PCHPPCHYIPR-NH2 with a disulfide bridge, the Cys–His motif was found to be crucial for the
coordination of Ni2+ ions. In the case of the N-unprotected analogues, the N-terminal amino group
participates in the coordination as well
In vitro activity of amphibian peptides alone and in combination with antimicrobial agents against multidrug-resistant pathogens isolated from surgical wound infection.
No full textThe in vitro activities of three amphibian peptides magainin II amide, citropin 1.1 and temporin A alone and in combination with eight clinically used antimicrobial agents (imipenem, ceftazidime, clarithromycin, vancomycin, amikacin, polymyxin E, ciprofloxacin and linezolid) were investigated against several multidrug-resistant Pseudomonas aeruginosa and Staphylococcus aureus strains isolated from surgical wound infections. Antimicrobial activities were measured by MIC, MBC and time-kill studies. P. aeruginosa strains were more susceptible to magainin II amide and less susceptible to temporin A. S. aureus isolates were highly susceptible to temporin A and citropin 1.1. The combination studies showed synergy between citropin 1.1 and clarithromycin. Magainin II amide and temporin A showed synergism with imipenem and ceftazidime. Finally, all peptides showed synergistic effects with polymyxin E. These results provide evidence for the potential use of these antimicrobial peptides in the topical or systemic treatment of surgical wound infections
The C terminus of HspA - A potential target for native Ni(II) and Bi(III) anti-ulcer drugs
No full textHspA, a protein crucial for nickel homeostasis in Helicobacter pylori (H. pylori), has a unique histidine- and cysteine-rich domain at the C terminus. In this work, we compared the coordination of
nickel (the natural co-factor) and bismuth (inhibitor) to this domain (Ac-ACCHDHKKH-NH2) and to a reference peptide (Ac-CHCH-NH2). Potentiometric, CD, UV-Vis spectroscopic and NMR methods have shown that bismuth binds incomparably stronger than nickel; the same data shows the impact of histidines on such a binding. Our results are in good agreement with earlier biological data and suggest
that HspA can be a potential target of the bismuth anti-ulcer drug against H. pylori
Copper binding to chicken and human prion protein amylodogenic regions: differences and similarities revealed by Ni2+ as a diamagnetic probe
No full textBoth human (h) and chicken (Ch) prion proteins (PrP) bind copper ions within the so called ‘‘tandem repeat” N-terminal region. Outside this region, hPrP possesses two additional copper binding sites, localized
at His-96 and His-111 in the so called ‘‘amylodogenic” or neurotoxic region (residues 91–126). Also ChPrP possesses a similar region (ChPrP105140) containing two His (His-110 and His-124) and an identical hydrophobic tail of 15 amino acids rich in Ala and Gly. The copper binding abilities within such region of ChPrP were investigated by NMR, CD and potentiometry using Ni2+ as diamagnetic probe.
The formation of diamagnetic metal complexes allowed to monitor the chemical shift and signal intensity variations and to determine the structural and kinetic features of the His-110 and His-124 metal binding
sites. Finally a comparison between the hPrP and ChPrP metal binding abilities was performed. We found that the two prion proteins exhibited different copper and nickel preferences with the favoured metal
binding sites localized at opposite His: His-110 for ChPrP, and His-111 for hPrP
The His-His sequence of the antimicrobial peptide demegen P-113 makes it very attractive ligand for Cu2+
No full textHistatins are a family of histidine-rich, cationic peptides up to 38 amino acids long. As other antimicrobial peptides histatins exhibit in vitro activity against both bacteria and yeasts. A 12 amino acid amidated fragment of histatin 5, designated P-113 or demegen, has been identified as the smallest fragment retaining antimicrobial activity comparable to the parent compound. Demegen, AKRHH-GYKRKFH, has three His and a N-terminal group known to participate in copper ion coordination. In this study potentiometric and spectroscopic (UV-vis, CD, EPR, NMR) measurements were used to evaluate the stability constants, stoichiometry and structures of Cu2+ Complexes with dernegen P-113 and its analogues in aqueous solution. The main aim of this work was to understand the role of two adjacent histidine residues in metal ion binding. The comparison with results for modified ligands showed that two histydyl residues are basic for complex formation in the 4.5-7 pH range. (C) 2008 Published by Elsevier Inc
Synergic combinations of antimicrobial peptides (AMPs) against biofilms of methicillin-resistant Staphylococcus aureus (MRSA) on polystyrene and medical devices
No full text
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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