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Becucci L.,University of Florence | Valensin D.,Chemistry and Pharmacy | Innocenti M.,University of Florence
Soft Matter | Year: 2014

The mechanism of membrane permeabilization by dermcidin (DCD-1L), an antimicrobial peptide present in human sweat, was investigated at a mercury-supported monolayer of dioleoylphosphatidylcholine (DOPC) or dioleoylphosphatidylserine (DOPS) and at a mercury-supported tethered bilayer lipid membrane (tBLM) consisting of a thiolipid (DPTL) with a DOPC or DOPS monolayer self-assembled on top of it. In an unbuffered solution of pH 5.4, DCD-1L is almost neutral and permeabilizes a DPTL/DOPS tBLM at transmembrane potentials, φtrans, which are physiological. In a pH 7 buffer solution DCD-1L bears two negative charges and has no effect on a DPTL/DOPC tBLM, whereas it permeabilizes a DPTL/DOPS tBLM only outside the physiological φtrans range; however, the presence of zinc ion induces DCD-1L to permeabilize the DPTL/DOPS tBLM at physiological φtrans values. The effect of zinc ions suggests a DCD-1L conformation with its positive N-terminus embedded in the lipid bilayer and the negative C terminus floating on the membrane surface. This conformation can be stabilized by a zinc ion bridge between the His38 residue of the C terminus and the carboxyl group of DOPS. Chronocoulometric potential jumps from φtrans ≅ +160 mV to sufficiently negative values yield charge transients exhibiting a sigmoidal shape preceded by a relatively long "foot". This behavior is indicative of ion-channel formation characterized by disruption of DCD-1L clusters adsorbed on top of the lipid bilayer, incorporation of the resulting monomers and their aggregation into hydrophilic pores by a mechanism of nucleation and growth. © 2014 The Royal Society of Chemistry.

Potocki S.,Wroclaw University | Valensin D.,Chemistry and Pharmacy | Kozlowski H.,Wroclaw University
Dalton Transactions | Year: 2014

The Zrt/Irt-like protein (ZIP) family contributes to the metal homeostasis by regulating the transport of divalent metal cations such as Fe2+, Zn2+, Mn2+, Cd2+ and sometimes even Cu 2+. Most ZIP members have a long variable loop between transmembrane domains (TMDs) III and IV; this region is predicted to be located in the cytoplasm and is postulated to be the metal ion binding site. In this study, we looked at the thermodynamic behavior and coordination chemistry of Zn 2+, Ni2+ and Cu2+ complexes with the histidine-rich domain, Ac-(185)RAHAAHHRHSH(195)-NH2 (HRD), from the yeast TjZNT1 protein, located between TMDs III and IV. The sequence is conserved also in higher species like Thlaspi japonicum. The stability of complexes increases in the series Ni2+ < Zn2+ ≪ Cu 2+. The geometry of complexes is very different for each metal and in the case of Zn2+ complexes, high specificity in binding is observed. Moreover, the stability of HRD-Cu2+ complexes was compared with the five His residues containing peptide from Hpn protein (Helicobacter pylori). The results suggest a high ability of HRD in the binding of all three studied metals. © 2014 The Royal Society of Chemistry.

Rossi C.,Chemistry and Pharmacy | Rossi C.,University of Florence | Bonechi C.,Chemistry and Pharmacy | Bonechi C.,University of Florence | And 4 more authors.
Macromolecular Symposia | Year: 2014

Biomacromolecules in solution modify the structure and the dynamics of the bulk water at the solute-solvent interface. The ordering effects of biomolecules, in particular proteins, are extended for several angstroms. The role of the hydration shells around a protein has yet to be completely understood. Hydrated proteins maintain more dynamic flexibility with respect to the dried system, which is an important property in protein-protein and/or protein-ligand recognition processes. In this paper we propose a method for analyzing the dynamical properties of the water molecules present in the hydration shells of proteins. The approach is based on analysis of the effects of protein-solvent interactions on water protons NMR relaxation parameters. The water proton spin-lattice relaxation rate in protein solution is analyzed considering all possible dipolar contributions from coupled protons environments. The analysis of both selective and non-selective water spin-lattice relaxation rates allowed the calculation of the average effective correlation time for the water molecules at the protein interface and the evaluation of the long range ordering effect of the protein surface. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Svane S.,Chemistry and Pharmacy | Kryuchkov F.,Campusvej | Lennartson A.,Chemistry and Pharmacy | McKenzie C.J.,Chemistry and Pharmacy | Kjeldsen F.,Campusvej
Angewandte Chemie - International Edition | Year: 2012

Complex protection: Fragmentation of phosphorylated peptide ions by collision-activated dissociation (CAD) is possible without facile detachment of the phosphate ester group when it is protected by a digallium complex (see scheme). The application of this dimetal phosphate ester stabilization (DIMPES) approach is believed to hold enormous potential for application in phosphoproteomics. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Stokowa-Soltys K.,Wroclaw University | Gaggelli N.,Chemistry and Pharmacy | Nagaj J.,Wroclaw University | Szczepanik W.,Wroclaw University | And 6 more authors.
Journal of Inorganic Biochemistry | Year: 2013

Three representatives of the distinct antibiotics groups: amoxicillin, apramycin and ristomycin A were studied regarding their impact on hepatitis D virus (HDV) ribozyme both in the metal-free form and complexed with copper(II) ions. Hence the Cu(II)-ristomycin A complex has been characterized by means of NMR, EPR, CD and UV-visible spectroscopic techniques and its binding pattern has been compared with the coordination modes estimated previously for Cu(II)-amoxicillin and Cu(II)-apramycin complexes. It has thus been found that all three antibiotics bind the Cu(II) ion in a very similar manner, engaging two nitrogen and two oxygen donors into coordination with the square planar symmetry in physiological conditions. All three tested antibiotics were able to inhibit the HDV ribozyme catalysis. However, in the presence of the complexes, the catalytic reactions were almost completely inhibited. It was important therefore to check whether the complexes used in lower concentrations could inhibit the HDV ribozyme catalytic activity, thus creating opportunities for their practical application. It turned out that the complexes used in the concentrations of 50 μM influenced the catalysis much less effectively comparing to the 200 micromolar concentration. The kobs values were lower than those observed in the control reaction, in the absence of potential inhibitors: 2-fold for amoxicillin, ristomycin A and 3.3-fold for apramycin, respectively. © 2013 Elsevier Inc.

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