Search results for " bonding"
showing 10 items of 934 documents
Hydrogen-Bonded Open-Framework with Pyridyl-Decorated Channels: Straightforward Preparation and Insight into Its Affinity for Acidic Molecules in Sol…
2017
International audience; An hydrogen-bonded open framework with pores decorated by pyridyl groups has been constructed following an off-charge-stoichiometry assemblage of protonated tetrakis(4-pyridyl-oxymethyl)methane and [Al(oxalate)3]3-, respectively the H-bond donor and acceptor of the ionic H-bond interactions. This supramolecular porous architecture (SPA-2) possesses 1 nm-large pores interconnected in 3D with high solvent accessible void (53%). It demonstrated remarkable affinity for acidic organic molecules in solution, which was investigated by the means of various carboxylic acids including larger drug molecules. Noteworthy, competing sorption between acetic acid and its halogenated…
Supramolecular assemblies and photophysical properties of ionic homo- and heteronuclear metallophilic complexes
2019
Abstract The synthesis of two dinuclear ionic complexes with chemical formula [Au(PR 3 ) 2 ][Au(C ≡ CC 5 H 4 N-4) 2 ] that contain the water soluble phosphines, PR 3 , PTA (1, 3,5-triaza-7-phosphaadamantane, 1 ) and DAPTA (3,7-diacetyl-1,3,7-triaza-5-phosphabicyclo[3.3.1]nonane, 2 ) is herein described. The differences on their intermolecular reorganization have been analyzed and compared with the previously reported for the neutral complexes [Au(PR 3 )(C ≡ CC 5 H 4 N-4)]. It has been evidenced that the reorganization of the ligands giving rise to the dinuclear ionic complexes produces a complete change in the properties giving rise to Au⋯Au intermolecular assemblies. These aurophilic conta…
Influence of the solvent and R groups on the structure of (carboranyl)R2PI2 compounds in solution. Crystal structure of the first iodophosphonium sal…
2008
The influence of the electron-donor or electron-acceptor capacity of the R groups (R = (i)Pr, Ph, Et) and the solvent on the molecular geometry in solution of adducts of carboranylphosphanes [(carboranyl)(i)Pr2P, (carboranyl)Ph2P and (carboranyl)Et2P] with I2 in 1 : 1 ratios, has been studied in detail by 31P{1H} and 11B{1H} NMR spectroscopies. The more electron-accepting Ph groups make the (carboranyl)Ph2P less nucleophilic, thus stabilizing the I2 encapsulated neutral biscarboranylphosphane-diiodine adducts in solution, such as (carboranyl)Ph2PI-IPPh2(carboranyl), generating P---I-I---P motifs. Even in a polar solvent, such as EtOH, the arrangement is preserved. The expected basicity of t…
A delamination test for structural wood adhesives used in thick joints
2001
A test method was developed for the measurement of delamination of structural wood adhesives applied in thick joints. Large differences were observed within a range of 8 commercial epoxy-based products.
Effect of different concentrations of specific inhibitor of matrix metalloproteinases on the shear bond strength of self-adhesive resin cements to de…
2017
Background Considering the probability of chemical and enzymatic reactions between matrix metalloproteinases (MMPs) in the dentin structure and their specific inhibitors, the aim of the present study was to evaluate the effect of different concentrations of specific inhibitor of MMPs (galardin) on the shear bond strength of self-adhesive resin cements to dentin. Material and Methods Forty-eight sound human premolars were mounted in self-cured acrylic resin after removal of the enamel on the buccal and lingual surfaces. The dentin surfaces achieved were polished and prepared with 600-grit silicon carbide paper. The samples were divided into 3 groups (n=16) based on the concentration of galar…
Uncovering Technological and Environmental Potentials of Aluminum Alloy Scraps Recycling Through Friction Stir Consolidation
2020
Conventional metal chips recycling processes are energy-intensive with low efficiency and permanent material losses during re-melting. Solid state recycling allows direct recycling of metal scraps into semi-finished products. It is expected that this process category would lower the environmental performance of metals recycling. Friction Stir Consolidation is a new solid-state technique taking advantage of friction heat generation and severe plastic deformation to consolidate chips into billets. In this research, the feasibility of Friction Stir Consolidation as aluminum chips recycling process is analyzed. Specifically, an experimental campaign has been carried out with varying main proces…
Onset of cohesion in cement paste
2004
It is generally agreed that the cohesion of cement paste occurs through the formation of a network of nanoparticles of a calcium-silicate-hydrate ("C-S-H"). However, the mechanism by which these particles develop this cohesion has not been established. Here we propose a dielectric continuum model which includes all ionic interactions within a dispersion of C-S-H particles. It takes into account all co-ions and counterions explicitly (with pure Coulomb interactions between ions and between ions and the surfaces) and makes no further assumptions concerning their hydration or their interactions with the surface sites. At high surface charge densities, the model shows that the surface charge of…
The open metastable structure of a collapsible sand: fabric and bonding
2015
This paper deals with the compositional and textural characteristics determining open metastable structures in the pleistocenic sand outcropping in the Agrigento district (Sicily). The aim of the study was to individuate the bonding types occurring between grains that could generate matric suction phenomena. The composition and microfabric were characterised by means of granulometry, porosimetry, permeability, optical and ESEM-EDS microscopy, thermogravimetry and XR diffractometry, electric conductivity, and ionic chromatography. The data thus acquired show that the skeleton of the sand is constituted mostly by bioclasts and microfossils, calcite and quartz monocrystalline grains. Moreover,…
Stability of a Split Streptomycin Binding Aptamer
2016
Here we investigated the stability of an aptamer, which is formed by two RNA strands and binds the antibiotic streptomycin. Molecular dynamics simulations in aqueous solution confirmed the geometry and the pattern of hydrogen bond interactions that was derived from the crystal structure (1NTB). The result of umbrella sampling simulations indicated a favored streptomycin binding with a free energy of ΔGbind° = −101.7 kJ mol–1. Experimentally, the increase in oligonucleotide stability upon binding of streptomycin was probed by single-molecule force spectroscopy. Rate dependent force spectroscopy measurements revealed a decrease in the natural off-rate (koff-COMPLEX = 0.22 ± 0.16 s–1) for the …
Development of Novel Peptide-Based Michael Acceptors Targeting Rhodesain and Falcipain-2 for the Treatment of Neglected Tropical Diseases (NTDs)
2017
This paper describes the development of a class of peptide-based inhibitors as novel antitrypanosomal and antimalarial agents. The inhibitors are based on a characteristic peptide sequence for the inhibition of the cysteine proteases rhodesain of Trypanosoma brucei rhodesiense and falcipain-2 of Plasmodium falciparum. We exploited the reactivity of novel unsaturated electrophilic functions such as vinyl-sulfones, -ketones, -esters, and -nitriles. The Michael acceptors inhibited both rhodesain and falcipain-2, at nanomolar and micromolar levels, respectively. In particular, the vinyl ketone 3b has emerged as a potent rhodesain inhibitor (k2nd = 67 × 106 M-1 min-1), endowed with a picomolar b…