Search results for "Titration"
showing 10 items of 312 documents
Structure of SNX9 SH3 in complex with a viral ligand reveals the molecular basis of its unique specificity for alanine-containing class I SH3 motifs
2021
Class I SH3 domain-binding motifs generally comply with the consensus sequence [R/K]x0PxxP, the hydrophobic residue 0 being proline or leucine. We have studied the unusual 0 = Ala-specificity of SNX9 SH3 by determining its complex structure with a peptide present in eastern equine encephalitis virus (EEEV) nsP3. The structure revealed the length and composition of the n-Src loop as important factors determining specificity. We also compared the affinities of EEEV nsP3 peptide, its mutants, and cellular ligands to SNX9 SH3. These data suggest that nsP3 has evolved to minimize reduction of conformational entropy upon binding, hence acquiring stronger affinity, enabling takeover of SNX9. The R…
Bis(terpyridyl)-ruthenium(II) units attached to polyazacycloalkanes as sensing fluorescent receptors for transition metal ions
2000
A synthetic strategy has been devised for the preparation of new compounds in which terpyridyl fragments are linked to 1,4,8,11-tetraazacyclotetradecane (cyclam). Reaction of excess cyclam with 4′-[(4-bromomethyl)phenyl]-2,2′:2″,6′-terpyridine afforded the ligand 1-[4′-p-tolyl-(2,2′:6′,2″-terpyridyl)]-1,4,8,11-tetraazacyclotetradecane (L1) in which the tetraaza macrocycle was covalently attached to one benzyl-terpyridyl fragment. Under similar conditions reaction of cyclam with excess 4′-[(4-bromomethyl)phenyl]-2,2′:2″,6′-terpyridine gave the tetra substituted cyclam derivative 1,4,8,11-[4′-p-tolyl-(2,2′:6′,2″-terpyridyl)]-1,4,8,11-tetraazacyclotetradecane (L2). The multidentate ligand L2 w…
Flow injection spectrophotometric determination of boron in ceramic materials.
1998
Abstract A flow injection spectrophotometric method for the determination of boron in ceramic materials is described. The method is based on spectrophotometric measurement of the decrease in the pH produced by the reaction between boric acid and mannitol in the presence of an acid-base indicator. A bichannel FI (flow injection) manifold in which the sample solutions were injected into deionized water (at pH 5.4) and the stream was later merged with the reagent stream (a mannitol solution containing 1×10 −4 mol l −1 bromocresol green at pH 5.4), was used. Transient signals were monitored at 616 nm. A theoretical model which describes the dependence between the absorbance values and boric aci…
Determination of aniline in vegetable oils by diazotization and coupling in a microemulsion medium
1990
Abstract A microemulsion containing sodium dodecyl sulphate and n -pentanol in a mass ratio of 1 : 4, water and a vegetable oil was investigated using pseudo-tenary phase diagrams. The medium can co-solve important amounts of vegetable oils and aqueous solutions over a wide range of ionic strengths. A procedure for the determination of 1.4–140 μg ml −1 of aniline in vegetable oils using ionic diazotization and coupling reactions was developed. The absorbance was measured in an optically clear microemulsion containing 4% or 20% of oil. The procedure is much simpler and rapid than the official chromatographic methods and gives almost the same limits of detection (ca. 05 μg ml −1 ) using no mo…
Determination of -Ascorbic Acid in Lycopersicon Fruits by Capillary Zone Electrophoresis
2001
This study shows an improved method for the determination of L-ascorbic acid (l-AA) in fruits of Lycopersicon by capillary zone electrophoresis (CZE). Two backgrounds electrolytes (BGEs) have been tested: (i) 400 mM borate at pH 8.0 and 1 x 10(-2)% hexadimethrine bromide, for the separation of Eulycopersicon subgenus species; and (ii) as in BGE(i) but supplemented with 20% (v/v) acetonitrile, for the separation of species of the Eriopersicon subgenus. The present procedures were compared with two routine methods-enzymatic assay and potentiometric titration with 2,6-dichlorophenol-indophenol. While these routine methods presented some difficulties in quantifying l-AA in several Lycopersicon …
Deprotonation of resorcinarenes by mono- and diamine bases: complexation and intermolecular interactions in the solid state
2014
The deprotonation of resorcinarenes by mono- and dibasic amines, viz. triethylamine (TEA) and its dibasic analogue, N,N′-dimethylpiperazine (DMPip), was studied and the resulting supramolecular complexes were analysed in the solid state, in solution and in the gas phase. In the solid state, 1:1 (2TEAH+·(ethyl-resorcinarene)2−·MeOH), 3:2 [DMPip·2DMPipH+·2(ethyl-resorcinarene−)] and 3:2 [2DMPip·DMPipH22+@(2methyl-ethyl-resorcinarene−)2·2MeOH] solid state complexes and interesting resorcinarene−⋯resorcinarene− supramolecular networks formed via enhanced hydrogen bonds involving the hydroxyl groups and the deprotonated hydroxyl groups of the resorcinarenes were observed. The host–guest complexe…
Thermometric study of the dissociation equilibria of the maleinimidodioxime
1982
The values of the dissociation constants of the maleinimidodioxime are potentiometrically determined at various ionic strengths, and extrapolated to zero ionic strength (pK1T=10.41;pk2T=11.60). From these values and from the thermometric titration curves the enthalpies of neutralization (ΔHN1=−21.76,ΔHN2=−23.77 kJ/mol) and the thermodynamic parameters of dissociation of this substance at 25.0 °C are determined (ΔG1θ=59.41,ΔG2θ=66.23,ΔH1θ=34.06,ΔH2θ=32.05 kJ/mol;ΔS1θ=−85.06,ΔS2θ=−114.64 J/(K mol)).
Calcification is not the Achilles'heel of cold-water corals in an acidifying ocean
2015
Ocean acidification is thought to be a major threat to coral reefs: laboratory evidence and CO2 seep research has shown adverse effects on many coral species, although a few are resilient. There are concerns that cold-water corals are even more vulnerable as they live in areas where aragonite saturation (Omega ara) is lower than in the tropics and is falling rapidly due to CO2 emissions. Here, we provide laboratory evidence that net (gross calcification minus dissolution) and gross calcification rates of three common cold-water corals, Caryophyllia smithii, Dendrophyllia cornigera, and Desmophyllum dianthus, are not affected by pCO2 levels expected for 2100 (pCO2 1058 µatm, Omega ara 1.29),…
Ocean acidification affects fish spawning but not paternity at CO2 seeps
2016
Fish exhibit impaired sensory function and altered behaviour at levels of ocean acidification expected to occur owing to anthropogenic carbon dioxide emissions during this century. We provide the first evidence of the effects of ocean acidification on reproductive behaviour of fish in the wild. Satellite and sneaker male ocellated wrasse (Symphodus ocellatus) compete to fertilize eggs guarded by dominant nesting males. Key mating behaviours such as dominant male courtship and nest defence did not differ between sites with ambient versus elevated CO2 concentrations. Dominant males did, however, experience significantly lower rates of pair spawning at elevated CO2 levels. Despite the higher r…
Understanding the Solution Behavior of Epinephrine in the Presence of Toxic Cations: A Thermodynamic Investigation in Different Experimental Conditio…
2020
The interactions of epinephrine ((R)-(&minus