Search results for " solution"
showing 10 items of 3084 documents
Thermodynamics of copolymer solutions: how the pair interactions contribute to the overall effect.
2014
Vapor pressure measurements were performed for solutions of poly(methyl methacrylate-ran-tert-butyl methacrylate) with different weight fractions of tert-butyl methacrylate units, and their parental homopolymers in chloroform at 323 K, over a large domain of concentrations. The Flory–Huggins interaction parameters obtained from these experimental investigations show complex dependences of the Flory–Huggins interaction parameter on concentration and copolymer composition. This behavior can be modeled by taking into account an approach which considers the ability of the polymers to rearrange in a response to changes in their molecular surroundings [Adv. Polym. Sci. 2011, 238, 1–66]. According…
Bis(oxalato)chromium(III) complexes: Versatile tectons in designing heterometallic coordination compounds
2011
Abstract The mononuclear oxalato-containing chromium(III) complexes of general formula [Cr(AA)(C2O4)2]− (AA = α-diimine type ligand) are able to produce a large variety of heterometallic complexes by acting as ligands towards either fully solvated metal ions or preformed cationic complexes with available coordination sites. This review focuses on the structural diversity of the polynuclear complexes (oligonuclear and coordination polymers) which are generated by the bis(oxalato)chromate(III) species, with a special emphasis to their magnetic properties.
Solution properties of polyelectrolytes
1991
Abstract Chromatographic data for sodium polystyrene sulphonate were obtained on both silica- and polymer-based size-exclusion supports using mobile phases of various pH and ionic strength. Deviations of the elution volume were observed towards both lower and higher values relative to the reference calibration graph obtained with uncharged standards. An empirical correlation is proposed in order to account for all the secondary effects observed. The general applicability of this correlation was further tested for chromatographic data obtained for a series of peptides and proteins on a silica-based support under very different eluent conditions. Deviations from ideal elution behaviour such a…
Application of a weakly basic dimethylamino-modified silica ion exchanger to the separation of oligonucleotides
1979
Abstract LiChrosorb RP-8, RP-18 and Diol as well as a newly synthesized basic dimethylamino-modified silica ion-exchanger (DMA-silica) were applied for the separation of adenylic acid, cytidylic acid and uridylic acid oligoribonucleotides. On LiChrosorb RP-8 and RP-18, respectively, in aqueous buffered eluents (K 2 HPO 4 - H 3 PO 4 ), the retention of oligonucleotides was increased with decreasing number of nucleotide units in the solute, i.e., with increasing hydrophobic character. The elution behaviour of ologonucleotides on LiChrosorb Diol followed the same order but took place according to a size-exclusion mechanism. The retention of oligonucleotides on DMA-silica is assumed to be based…
Interactions between non-volatile water-soluble molecules and aroma compounds in Camembert cheese
2002
Abstract Interactions between selected aroma compounds and non-volatile water-soluble molecules were studied using dynamic headspace-gas chromatography. A model water-soluble extract (MWSE), previously constructed in gustatory and physico-chemical accordance with the crude Camembert cheese WSE, allowed the contribution of non-volatiles to the headspace composition of volatile compounds to be assessed. The presence of the MWSE increased the headspace concentration of 2-heptanone, 1-octen-3-ol and 3-methylbutanol, showing that these three volatile compounds were released by MWSE. Omission tests performed on MWSE allowed for the impact of each MWSE component on aroma compounds release to be de…
Determination of the four major surfactant classes in cleaning products by reversed-phase liquid chromatography using serially connected UV and evapo…
2016
Abstract A method for the simultaneous determination of the most frequently used surfactant families –linear alkyl benzenesulphonates (LAS), alkyl ether sulphates (AES), fatty alcohol ethoxylates (FAE) and oleins (soaps, fatty acid salts) – in cleaning products, has been developed. The common reversed phase octyl (C8), pentafluorophenyl and biphenyl columns were not capable of separating the anionic LAS and AES classes; however, since only LAS absorbs in the UV, these two classes were independently quantified using a C8 column and serially connected UV and ELSD detection. The best compromise to resolve the four surfactant classes and the oligomers within the classes was achieved with a C8 c…
Solvent quality as reflected in concentration- and temperature-dependent Flory-Huggins interaction parameters
2001
Flory-Huggins interaction parameters (χ) between poly(dimethylsiloxane) (weight-average molecular weight = 152 kg/mol) and various solvents (methyl ethyl ketone, toluene and n-octane) were determined as a function of composition and temperature with vapor-pressure measurements. These data, complemented by independent information for dilute and very concentrated solutions, serve as the basis for a discussion of solvent quality via different theoretical relations. Regardless of polymer concentration, the χ values fall from methyl ethyl ketone via toluene to n-octane, the ketone being the worst solvent and the hydrocarbon being the best solvent. The variation of χ with composition and temperat…
Keyhole Limpet Hemocyanin (KLH): Slow In Vitro Reassociation of KLH1 and KLH2 from Immucothel®
1998
Abstract Following our in vitro reassociation of keyhole limpet hemocyanin subunits in the presence of high concentrations (100 mM each) of calcium and magnesium chloride (Harris et al., 1997a, Micron 28, 31–41; 1997b, Micron 28, 43–56), we have now extended our investigations by using a buffer system containing a lower concentration of the two divalent cations (10 mM each). Reassociation of mixed KLH subunits present in the commercially available product Immucothel® was performed using a standardized buffer solution containing 50 mM Tris–HCl, 150 mM NaCl, 10 mM CaCl2 and 10 mM MgCl2 (pH 7.4) over a minimum period of one week, at 4°C. This solution was selected as being close to our KLH sta…
A micellar liquid chromatographic method for quality control of pharmaceutical preparations containing tricyclic antidepressants
2002
Micellar liquid chromatography methods for quality control of pharmaceutical preparations (capsules, pills, tablets, injections) containing the tricyclic antidepressants amineptine, amitriptiline, clomipramine, doxepin, imipramine, melitracen and nortriptyline alone or together with other CNS drugs like diazepam, medazepam and perphenazine are described. The methods using micellar solutions of cetyltrimethylammonium bromide as mobile phases and UV detection are rapid and reproducible. Due to the versatility of interactions in micellar liquid chromatography, it is possible determine highly hydrophobic compounds such as TCAs in a short time using mobile phases containing low organic solvent c…
Stabilization of an ?-helical conformation in an isolated hexapeptide inhibitor of calmodulin
2001
The conformational properties of two hexapeptides, Ac-LWRILW-NH(2) and its D-amino acid counterpart Ac-lwrilw-NH(2), identified as calmodulin inhibitors using mixture-based synthetic combinatorial library approaches, have been characterised by NMR and CD spectroscopy. The peptides fold into an alpha-helical conformation in aqueous solution. The observed short- and medium-range nuclear Overhauser effects were consistent with the formation of an alpha-helical structure and a reasonably well-defined set of structures was obtained by using restraints from the NMR data in simulated annealing calculations. Analysis of glycine-substitution analogues demonstrated that all the amino acids that make …