Presence Of Acetate Ions Research Articles

Albumin and mucin at the polarized mercury/water interface

The adsorption of bovine serum albumin and submaxillary mucin at a polarized mercury/water interface was studied using ac polarography. The two biopolymers saturated the surface at solute concentrations of about 0.2 mg/ml and remained adsorbed in 0.1 M salt solutions over a wide range of polarization. A large current at −1.7 V was observed at acidic pH's in the presence of acetate ions. Increasing ionic strength one order of magnitude led to a several-fold increase in the current. The effects of pH and ionic strength on the current can be explained in terms of the catalytic reduction of hydrogen ions due to the adsorbed biopolymers. The albumin and mucin, which are both proteinaceuous, show similar adsorption ranges and catalytic currents at the mercury/water interface. Extrinsic membrane proteins may have related properties that contribute to the observed changes in structure upon polarization.

Polymer supported metal complexes as catalysts for oxidation of thiosalts by molecular oxygen. III. Comparative kinetic studies with poly(4-vinyl pyridine)-Cu(II) complex

Abstract A water-insoluble copper(II) complex, prepared by cross-linking poly(4-vinyl pyridine) with copper sulfate, has been used as a catalyst for oxidation of thiosalts by molecular oxygen at ambient temperatures. This polychelate has been found to catalyze oxidation of sulfite (SO2−3), thiosulfate (S2O2−3), dithionite (S2O2−4), disulfite (S2O2−5), trithionate (S3O2−6) and tetrathionate (S4O2−6) to sulfate (SO2−4). The kinetics of oxidation of S2O2−3, S3O2−6 and S4O2−6 has been studied in the presence of the catalyst. In each case the initial rate behavior is well explained by a Langmuir—Hinshelwood type rate law. The differences in the rate of oxidation of these thiospecies appear to arise mainly from the differences in their adsorption behavior on the catalyst. Two mechanistic pathways are proposed for the oxidation of S2O2−3, one involving a direct electron transfer from S2O2−3 to Cu(II) and another involving electron transfer from S2O2−3 to O2 through the central Cu(II) atom in a Cu(Py)n(S2O2−3)(O2) complex. The initial concentration of S2O2−3 influences the reaction mechanism and the product distribution pattern, a lower concentration favoring its oxidation to SO2−4 over that to S4O26. The rate of oxidation is mildly augmented by the acidity of the reaction medium down to a pH of 2.0, but it falls abruptly thereafter due to the decomposition of the complex. The presence of acetate ions in the reaction medium produces a marked promotional effect on the catalytic oxidation of S2O2−3 to SO2−4, but it greatly inhibits the oxidation of S3O2−6.

Structural studies of staphylococcal protease. III. Binding of anions to the spin-labeled enzyme

The staphylococcal protease was coupled at the active-site serine residue with a spin-labeled analog of diisopropyl fluorophosphonate and the interaction of competitive inhibitors such as chloride and acetate anions, as well as N-carbobenzoxy-L-glutamic acid (Z-L-Glu), was investigated by electron paramagnetic resonance spectroscopy. It was observed that the addition of chloride ions to the spin-labeled enzyme increased the freedom of motion of the spin label while the presence of acetate ions and Z-L-Glu resulted in an increase in the immobilization of the spin label. These results suggest that these ions bind to the active site region in different ways.

Influence of some chelates of aluminium on the sorption of phosphate by hydrous Al‐oxides

AbstractSorption of phosphate by hydrous oxides of aluminium was studied as a function of pH, presence of chelates of aluminium and of the specific surface areas of the oxides.Aluminon was most effective in reducing P sorption followed by oxalic acid and EDTA. Acetylacetone, 8‐hydroxyquinoline, salicylic acid and fluoride affected little P sorption. The sorption was found to be higher the higher the value of the specific surface area of the oxide, but the shape of the sorption curve was the same for all the oxides studied, exhibiting a maximum at about pH 5. This maximum was found to coincide with the point of zero charge as determined in the presence of acetate ions. The sorption data are explained in terms of a ligand exchange mechanism in which phosphate chemisorbs on surface aluminium atoms displacing uncharged surface hydroxyls.

Kinetics of incorporation of zinc(II) into tetraphenylporphine in N,N-dimethylformamide. I. Monohydroxo and acetato complexes.

The kinetics of incorporation of zinc (II) into meso-tetraphenylporphine in N, N-dimethylformamide (DMF), at 30°, were affected by the trace water in the solvent and by the presence of acetate ion (OAc-). The reaction was one half order in Zn (ClO4)2·6H2O, whereas first order in Zn (ClO4)2·6DMF. Addition of HClO4 to the water containing system retarded the reaction rate and converted the kinetics to the first order with respect to total Zn (II). The main path for the reaction of Zn (ClO4)2·6H2O was concluded to be that involving the monohydroxo species, Zn (OH)+. Addition of acetate anion increased the rate, until at a ratio [OAc-]/[Zn] of unity the rate reached a maximum ; an increase of the ratio past unity caused a rate decrease. The species, Zn (OAc)+, is concluded to be more reactive than the fully solvated Zn (II) species and Zn (OAc)2·

METHYLMERCURY: PHOTOCHEMICAL TRANSFORMATION OF MERCURIC SULFIDE INTO METHYLMERCURY IN AQUEOUS SOLUTIONS1

Abstract. The photochemical reaction of mercuric sulfide was studied in aqueous solutions. The photo‐solubilization of mercuric sulfide occurred under irradiation with light of ≤650nm and was enhanced in the presence of oxygen and electrolytes. The resultant mercuric ions were easily methylated in the presence of acetate ions via the photosensitized reaction by the simultaneously produced “photo‐sulfur” under irradiation with light of ≤420nm. The photoelectrochemical studies of mercuric sulfide electrode revealed that black mercuric sulfide was an n‐type semiconductor and the photo‐current due to the dissolution as mercuric ions was observed on anodic polarization. The photo‐solubilization of mercuric sulfide may be interpreted in terms of the local‐cell mechanism.

Kinetics and mechanism of the acetate catalysed hydrolysis of 4-methoxyphenyl chloroformate and 4-methoxyphenyl fluoroformate in aqueous dioxan. Evidence for rate-determining attack of acetate ions on an intermediate mixed anhydride

Esters of fluoroformic acid hydrolyse more rapidly than the corresponding chloroformate esters, suggesting that carbon–halogen bond breaking is not greatly advanced in the rate-determining step. The rate of reaction of 4-methoxyphenyl fluoroformate with aqueous dioxan is markedly decreased in the presence of acetate ions whereas the rate of reaction of 4-methoxyphenyl chloroformate is increased. The rate curves for the latter reaction are sigmoid in shape. The results are interpreted in terms of the formation of an intermediate mixed anhydride for both reactions, which then undergoes nucleophilic attack by acetate ions to yield acetic anhydride and the phenol. This step is rate determining in the case of the fluoroformate.

Kinetics of bromine addition to unsaturated sulphones

The effect of added electrolytes on the kinetics of bromine addition to several α, β- and β,γ-unsaturated sulphones in glacial acetic acid at 30° has been studied. The presence of bromides leads to a general decrease in the rate of bromine addition, the decrease being pioportional to the concentration of the added bromide. This may be due to the decrease in the concentration of molecular bromine, the reactive electrophilic species, as a result of its combination with the bromide ion to form the tri-bromide (Br3 −) ion. The retarding effect (at a particular concentration) of the different bromides on the rate of bromine addition follows the order HBr > KBr > LiBr, probably due to the difference in the degree of dissociation of these bromides in glacial acetic acid. In the presence of acetate ions, there is a general increase in the rate of bromine addition to all the sulphones, presumably due to a salt effect. In the case of the sulphones having a nitro group and exhibiting a low electrophilic rate of bromine addition, the ratios of the rate constants of the acetate catalysed to uncatalysed additions are much higher than the ratios observed for other sulphones. The strikingly higher rate ratios observed for the nitrosubstituted sulphones indicate that in these compounds there is a considerable feasibility of a nucleophilic mode of addition by Br2OAc− ion. The effect of added lithium chloride seems to be somewhat complex.

Polarographic Reduction of Cobalt(II) in Acetonitrile in the Presence of Acetate Ions

Abstract The effect of the nature and the concentration of the supporting electrolyte on the polarographic reduction of cobalt(II) acetate in acetonitrile has been investigated. An acetonitrile solution of cobalt(II) acetate yields a two-step and a three-step reduction wave in 0.05m LiClO4 and in 0.05m NaClO4 solution, respectively. The same solution gives ill-defined reduction waves in the presence of quaternary ammonium perchlorates, such as (CH3)4NClO4, (C2H5)4NClO4, or (n-C4H9)4NClO4. The Co(CH3CN)n2+, Co(OAc)+, and Co(OAc)3−species are present in a solution containing alkali metal perchlorate electrolyte. Co(OAc)+ and Co(OAc)3− are the predominant species in a quaternary ammonium perchlorate solution. The reduction potential becomes more negative with increase in the number of acetate ions coordinated to cobalt(II). The reduction potential of cobalt(II) acetate becomes less negative upon the addition of alkali metal perchlorate to the quaternary ammonium perchlorate supporting electrolyte. This effect is caused by the dissociation reaction of cobalt(II) acetate, in which an acetate ligand is transferred to the alkali metal ion.

Longitudinal spin-lattice relaxation in aqueous solutions of dysprosium(III) and copper(II) ions as an indicator of complex formation

Spin-lattice relaxation times of aqueous solutions of Dy(III) and Cu(II) in the presence of acetate ions were determined. The experimental results suggest that the coordination number with respect to the acetate ion appears to be 3 and 2 for the Dy(III) and Cu(II) ion respectively.

Studies on the Kolbe Electrolytic Synthesis. IX. Comparison between Anodic and Peroxydisulfate Oxidation of Carboxylates; Kinetics of Peroxydisulfate Decomposition in the Presence of Acetate Ion.

Studies on the Kolbe Electrolytic Synthesis. IX. Comparison between Anodic and Peroxydisulfate Oxidation of Carboxylates; Kinetics of Peroxydisulfate Decomposition in the Presence of Acetate Ion.

Activation of Pitressin by Acetic Acid.

SummaryPitressin when boiled with acetic acid becomes more potent as shown by subcutaneous antidiuretic assay and intravenous pressor assay. These effects are not due to boiling, concentration, acidity, or the presence of acetate ions. The significance of these findings in connection with the preparation of acetic acid extracts of tissues for pitressin assay is discussed.

A Scopometric Method for the Estimation of Sugar in Urine.

The mercuric atom of the double mercuric-sodium chloride salt in carbonate solution is reduced by glucose at room temperature, giving a fine crystalline precipitate of mercurous chloride. This precipitate bears a quantitatively reproducible relation to the concentration of glucose which can be easily measured in the Junior Scopometer.1 With low concentration (circa. 5 mg. glucose per cc.) the turbidity is equivalent to 8 scale divisions per mg. on a wedge calibrated for urinary proteins precipitated by Exton's reagent and with high concentration (100 mg.) somewhat less than one scale division. This gives a wide range in its practical application and sensitiveness where this is most important for clinical interpretation.The microscopic crystalline precipitate consists of stubby needles when precipitated from a pure solution in the presence of certain colloids. Without the colloid the needles form crosses, and in the presence of acetate ions these fill out giving square plates with cross figures. The crysta...