Search results for "Bonding"
showing 10 items of 996 documents
Functional and dysfunctional conformers of human neuroserpin characterized by optical spectroscopies and Molecular Dynamics
2015
Neuroserpin (NS) is a serine protease inhibitor (SERPIN) involved in different neurological pathologies, including the Familial Encephalopathy with Neuroserpin Inclusion Bodies (FENIB), related to the aberrant polymerization of NS mutants. Here we present an in vitro and in silico characterization of native neuroserpin and its dysfunctional conformation isoforms: the proteolytically cleaved conformer, the inactive latent conformer, and the polymeric species. Based on circular dichroism and fluorescence spectroscopy, we present an experimental validation of the latent model and highlight the main structural features of the different conformers. In particular, emission spectra of aromatic res…
Thermodynamics of Proton Binding of Halloysite Nanotubes
2016
In this paper, new information on physical and chemical properties of the widely used nanostructured Halloysite mineral are reported. Given that the Halloysite has a tubular structure formed by a variable number of wrapped layers containing Si-OH and Al-OH groups, their proton binding affinity was measured at different ionic strengths and ionic media by means of potentiometric measurements in heterogeneous phase. One protonation constant for the Si-OH groups and two for the Al-OH groups were determined. The protonation constant values increase with increasing of the ionic strength in all the ionic media. This suggests that the presence of a background electrolyte stabilizes the protonated s…
Unravelling the GLY-PRO-GLU tripeptide induced reconstruction of the Au(110) surface at the molecular scale
2018
International audience; The adsorption of GLY-PRO-GLU tripeptide on Au(110) is investigated within the frame of all atom classical mechanics simulations and Density Functional Theory, focusing on the surface reconstruction. It is shown that the tripeptide adsorption reorganizes and restructures the Au(110) surface. A mechanism for the surface restructuration is proposed for both the neutral and zwitterionic form of the peptide at room temperature in Ultra High Vacuum. Diverse residues may be involved in the Au atoms displacement, and in particular glutamic acid, triggering a double proton transfer and the formation of a zwitter ionic state, is found to be responsible for the triggering of t…
The ins and outs of proton complexation
2009
Proton complexation differs from simple protonation by the fact that the coordinated hydrogen atom is bound intramolecularly to more than one donor atom. This is usually achieved by covalent bonding supplemented by hydrogen bonding. In a few cases, however, the complexed proton is hydrogen-bound to all donor atoms, which gives rise to single well (SWHB) and low barrier (LBHB) hydrogen bonds. This tutorial review highlights a full range of proton complexes formed with chelating and "proton-sponge"-type ligands, cryptand-like macropolycycles, and molecules of topological relevance, such as rotaxanes and catenanes. The concept of proton complexation can explain how the smallest cation possible…
Der Kindheitsfragebogen, ein Instrument zur Beschreibung der erlebten Kindheitsbeziehung zu den Eltern
2003
Zusammenfassung: Mit dem Kindheitsfragebogen (KFB) wird die erlebte Beziehung von erwachsenen Personen zu ihren Eltern in der Kindheit und Jugendzeit beschrieben. Es werden acht verschiedene Bereiche der Beziehungen zur Mutter bzw. zum Vater erfasst: Wahrgenommene Liebe, Strafverhalten, Elternteil als Vorbild, Bagatellisierung des Strafverhaltens, Ehrgeiz, Rollenumkehr, Kontrolle und Geschwisterrivalität. In vier weiteren Skalen wird die Ehe der Eltern beurteilt, der sozioökonomische Status des Elternhauses eingeschätzt sowie die soziale Unterstützung von außerhalb des Elternhauses und das Lebensgefühl in der Kindheit angegeben. In einer Stichprobe von 700 Patienten weisen die Skalen überw…
2,3,5,6-Tetrakis(2-pyridyl)pyrazine (tppz)-containing iron(II) complexes: Syntheses and crystal structures
2007
Abstract The preparation and crystal structure of two iron(II) complexes of formula PPh4-mer-[Fe(tppz)(CN)3] · 7H2O (1) and [Fe(tppz)2][Fe(NCS)4] (2) [tppz = 2,3,5,6-tetrakis(2-pyridyl)pyrazine; PPh 4 + = tetraphenylphosphonium cation ] are reported here. The structure of 1 consists of mononuclear mer-tricyano[2,3,5,6-tetrakis(2-pyridyl)pyrazine]ferrate(II) anions, tetraphenylphosphonium cations and crystallization water molecules. Three carbon atoms from three cyanide groups in a mer arrangement and three nitrogen atoms from a tridentate tppz ligand build a somewhat distorted octahedral surrounding around the iron atom in 1. The values of the Fe–C [1.925(6)–1.947(5) A] and Fe–N [1.870(4)–1…
Conformational and Tautomeric Control by Supramolecular Approach in Ureido-N-iso-propyl,N’-4-(3-pyridin-2-one)pyrimidine
2019
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Mechanical unfolding pathway of a model β-peptide foldamer.
2015
Foldamers constructed from oligomers of β-peptides form stable secondary helix structures already for small chain lengths, which makes them ideal candidates for the investigation of the (un)folding of polypeptides. Here, the results of molecular simulations of the mechanical unfolding of a β-heptapeptide in methanol solvent revealing the detailed unfolding pathway are reported. The unfolding process is shown to proceed via a stable intermediate even for such a small system. This result is arrived at performing non-equilibrium force ramp simulations employing different pulling velocities and also using standard calculations of the potential of mean force, i.e., the free energy as a function …
Crystal structure of 5′′-(4-chlorobenzylidene)-4′-(4-chlorophenyl)-1′-methyltrispiro[acenapthylene-1,2′-pyrrolidine-3′,1′′-cyclohexane-3′′,2′′′-[1,3]…
2015
In the title compound, C36H29Cl2NO4, two spiro links connect the methyl-substituted pyrrolidine ring to the acenaphthylene and cyclohexanone rings. The cyclohexanone ring is further connected to the dioxalane ring by a third spiro junction. The five-membered ring of the acenaphthylen-1-one ring system adopts a flattened envelope conformation, with the ketonic C atom as the flap, whereas the dioxalane and pyrrolidine rings each have a twist conformation. The cyclohexenone ring assumes a boat conformation. An intramolecular C—H...O hydrogen-bond interaction is present. In the crystal, molecules are linked by non-classical C—H...O hydrogen bonds, forming chains extending parallel to theaaxis.
Use of Catalyst in a 3D-QSAR Study of the Interactions between Flavor Compounds and β-Lactoglobulin
2003
This paper reports a 3D-QSAR study using Catalyst software to explain the nature of interactions between flavor compounds and beta-lactoglobulin. A set of 35 compounds, for which dissociation constants were previously determined by affinity chromatography, was chosen. The set was divided into three subsets. An automated hypothesis generation, using HypoGen software, produced a model that made a valuable estimation of affinity and provided an explanation for the lack of correlation previously observed between the hydrophobicity of terpenes and the affinity for the protein. On the basis of these results, it appears that aroma binding to beta-lactoglobulin is caused by both hydrophobic interac…