Search results for "solubility"
showing 10 items of 681 documents
Composés métallocèniques chalcogènés. Action des dihydrures de zirconocène et de hafnocène sur le soufre, le sélénium et le tellure
1989
Resume Dimeric zirconocene and hafnocene dihydrides [(η 5 -RC 5 H 4 ) 2 M(H)(μ-H)] 2 (M = Zr, Hf) react with grey selenium or tellurium to afford the known four-membered bimetallacyclic compounds [(η 5 -RC 5 H 4 ) 2 M(μ-E)] 2 (E = Se, Te) as the sole organometallic products. In the case of sulfur the first step of the reaction is shown to involve the insertion of a chalcogen atom into the metal-hydrogen bonds to give the bis-hydrogenosulfide (η 5 -t-BuC 5 H 4 ) 2 M(SH) 2 (M = Zr, Hf), which reacts either with the starting dihydride to give [(η 5 -t-BuC 5 H 4 ) 2 M(μ-S)] 2 or with the unchanged sulfur to afford the metallacyclohexasulfane (η 5 -t-BuC 5 H 4 ) 2 MS 5 and hydrogen sulfide. Thes…
Polysaccharide/polyaminoacid composite scaffolds for modified DNA release.
2009
Abstract In this work composite polymeric films or sponges, based on hyaluronic acid (HA) covalently crosslinked with α,β-poly(N-2-hydroxyethyl)(2-aminoethylcarbamate)- d , l -aspartamide (PE), have been prepared and characterized as local gene delivery systems. In particular, HA/PE scaffolds have been loaded with PE/DNA interpolyelectrolyte complexes, employing PE as a macromolecular crosslinker for HA and as a non-viral vector for DNA. In vitro studies showed that HA/PE films and sponges have high compatibility with human dermal fibroblasts and they give a sustained DNA release, whose trend can be easily tailored by varying the crosslinking ratio between HA and PE. Electrophoresis analysi…
Water-soluble isoindolo[2,1-a]quinoxalin-6-imines: In vitro antiproliferative activity and molecular mechanism(s) of action
2015
Abstract Water-soluble isoindoloquinoxalin (IIQ) imines and the corresponding acetates were conveniently prepared from the key intermediates 2-(2′-aminophenyl)-2H-isoindole-1-carbonitriles obtained by a Strecker reaction between substituted 1,2-dicarbaldehydes and 1,2-phenylenediamines. Both series were screened by the National Cancer Institute (Bethesda, MD) and showed potent antiproliferative activity against a panel of 60 human tumor cell lines. Several of the novel compounds showed GI50 values at a nanomolar level on the majority of the tested cell lines. Among IIQ derivatives, methoxy substituents at positions 3 and 8 or/and 9 were especially effective in impairing cell cycle progressi…
Mononuclear rearrangement of heterocycles in zwitterionic micelles of amine oxide surfactants.
2012
Abstract Rate constants for the mononuclear rearrangement (MRH) of Z -phenylhydrazones of some 5-substituted-3-benzoyl-1,2,4-oxadiazoles in water have been measured in the presence of zwitterionic micelles. The use of micellized N -tetradecyl- N , N -dimethylamineoxide (C 14 DMAO) as the reaction medium allowed to solubilize the otherwise water-insoluble oxadiazoles. Micellar rate effects were analyzed by using a simple pseudo-phase model and compared with those obtained in non-ionic micelles (Triton X-100). Evidence that both the rate of the rearrangement reaction and the binding of the substrates to the micelles are mainly governed by substrate hydrophobicity is obtained. The disagreement…
Tropylium cation capsule of hydrogen-bonded tetraurea calix[4]arene dimers
2001
The interaction between tropylium salts and tetraurea calix[4]arene derivatives (such as 1 and 2) was studied in solution using 1D, 2D, diffusion, VT NMR and UV–visible spectroscopy. It was found that tropylium salts form charge transfer complexes with both the monomers and dimers of the tetraurea calix[4]arene derivatives depending on the experimental conditions. Compound 1 increases dramatically the solubility of tropylium salts in apolar solvents such as C2D4Cl2, CDCl3 and CD2Cl2 by forming the molecular capsule 1·C7H7+·1. In contrast to the benzene capsule of 1, in 1·C7H7+·1 the hydrogen bonds in the equatorial region that hold together the two parts of the dimer change their directiona…
Interaction between biotin lipids and streptavidin in monolayers: formation of oriented two-dimensional protein domains induced by surface recognitio…
1989
Highly specific ligand-receptor interactions generally characterize surface recognition reactions. Such processes can be simulated by streptavidin-biotin-specific binding. Biotin lipids have thus been synthesized, and their interaction with streptavidin (or avidin) at the air-water interface was directly shown by measurement of surface pressure isotherms and fluorescence microscopy. These proteins interact with the biotin lipid monolayer via specific binding or nonspecific adsorption. Both phenomena were clearly distinguished by use of the inactivated form of streptavidin. The binding of fluorescein-labeled streptavidin to monolayers was also directly observed by fluorescence microscopy. Th…
A novel and simple method for the purification of extracellular levansucrase from Zymomonas mobilis.
2003
A new and simple method for the purification of extracellular levansucrase from Zymomonas mobilis from highly viscous fermentation broth was developed. After incubation of the fermentation broth with a fructose-polymer cleaving enzyme preparation (Fructozyme, Novozymes, DK) for 48 h, levansucrase precipitated as aggregates and was redissolved in a 3 M urea solution. By ongoing size-exclusion chromatography on Sephacryl S-300 the final levansucrase preparation was purified 100-fold and exhibited a specific activity of 25-35 U/mg(protein). The levansucrase was stable in 3 M urea solution for at least four months without inactivation. To maximize the enzyme yield the dynamic changes of extrace…
Synthesis, Optical and Electrical Properties of Oligo(phenylenevinylene)s Substituted with Electron-Accepting Sulfonyl Groups
2010
Oligo(phenylenevinylene)s (OPV) composed of five rings and electron donating or withdrawing sulfonyl substituents on the central and lateral rings have been investigated. Two strategies were used for the syntheses of the C2-symmetrical OPVs both include PO-activated olefinations as central steps. Six flexible side chains guarantee good solubility in toluene or dichloromethane. In solution and in films stabilised by polystyrene (60%), the chromophores are strongly fluorescent, with emissions in the violet-blue domain from solutions and in the green to orange region from solid films. The redox potentials, determined by cyclic voltammetry, and the optical properties are strongly depending on t…
In vitro performances and cellular uptake of clarithromycin nanocrystals produced by media milling technique
2018
Abstract Nanocrystal technology is one of a promising approach used to improve the solubility of poorly soluble drugs. In this study, media milling technique was used to produce clarithromycin nanocrystals via a bead milling machine. Various sizes of clarithromycin nanocrystals (250 nm–1 μm) were prepared using different milling times. The polymorphism and crystallinity of nanocrystals were characterized by powder X-ray diffraction (PXRD) and differential scanning calorimetry (DSC) techniques. The results indicated no polymorphic change after the milling process. However, the crystallinity of the obtained nanocrystals slightly decreased upon the milling time. The kinetic saturation solubili…
Molecular surface calculations on organic compounds
1992
Abstract The molecular surface area was calculated for 82 hydrocarbons, esters, ethers, alcohols and ketones including linear, branched and cyclic ones. The relationship between the aqueous solubility and the molecular surface area was determined for each family of compounds and for all the families together. The results show that solubility is mainly determined by molecular surface area and that the influence of functional group is the same for all the oxygen containing compounds studied.