Anionic Portion Research Articles

Kinetic studies on the reaction mechanism of the propionylcholinesterase from Hirudo medicinalis

1. Deacylation ( k′⪢ k) is the rate-limiting step of the hydrolysis of choline-containing substrates with Hirudo medicinalis propionylcholinesterase. Acylation occurs with those substrates containing p-nitrophenol. 2. Tetramethylanimonium and tetraethylammonium are competitive inhibitors for all substrates used. Tetrabutylammonium is competitive only for acetylthiocholine ( a=1), while a values with propionylthiocholine and butyrylthiocholine decrease from 0.375 to zero. 3. Two residues, p K = 6.47 and p K = 5, take part in the acylation in function of the pH. The residue involved in deacylation is characterized by p K = 4. 4. The anionic portion of the active site presents a p K < 4 and seems to have its principle effect on V, with non-coulombian forces having a role in the formation of the enzyme-substrate complex (ES). 5. Values relative to the enthalpy variation during the formation of ES and the deacylation are reported.

Crystal structure and infrared and Raman spectra of tetramethylammonium di-µ-fluoro-bis[aquadifluoro-oxovanadate(IV)

The title complex, [NMe4]2[V2O2F6(OH2)2], has been isolated from an aqueous solution of VF4 and [NMe4]F. The crystal structure has been determined from three-dimensional counter X-ray data. The compound crystallizes in the triclinic space group P with a= 7.012(1), b= 8.119(1), c= 9.047(1)A, α= 65.84(1), β= 83.21(1), γ= 73.09(1)°, and Z= 1. Least-squares refinement of the structure based on 1 552 observations led to an R factor of 0.046. The structure consists of dimeric units [{VOF3(OH2)}2]2– possessing a centre of inversion, which are linked in chains by short hydrogen bonds [O–H ⋯ F 2.564(5)A]. The geometry around vanadium is distorted octahedral with vanadium-fluorine distances ranging from 1.894(4) to 2.173(3), V–O 1.607(5), V–OH2 2.074(3), V–V 3.292(1)A, and V–F–V 105.5(1)°. The i.r. (250–4 000 cm–1) and Raman spectra of [NMe4]2[V2O2F6(OH2)2] and its deuteriated and anhydrous derivatives are reported and interpreted according to the structure. The spectrum of the cation shows only influences of the solid-state forces. Stretching vibrations of the VO bonds appear either in the Raman (980 cm–1) or the i.r. (968 cm–1). Hydrogen bonds give rise to a strong absorption manifesting one of the strongest interactions in hydrates (3 205 and 3 030 cm–1). The shift (νH/νD= 1.34) and the reduction in band width (factor of 1.8) upon deuteriation have expected values. The spectra of the product of reversible dehydration indicate the absence of a centre of inversion in the anionic portion.

Complexes of dibenzotetrathiafulvalene with chloroferrate anion

1. Some complexes of dibenzotetrathiafulvalene (DBTTF) with iron-containing anions were obtained. The complex (DBTTF)2.5[FeCl4], in which partial charge transfer exists, has a high electrical conductivity. 2. It was shown by the gamma resonance spectroscopy method that two states of trivalent iron are present in the anionic portion of the compound DBTTF2.5[FeCl4].

Kinetic analysis of differences in brain acetylcholinesterase from fish or mammalian sources

A kinetic analysis of the interactions of gold fish and rat brain AChE (acetylcholine acetylhydrolase, EC 3.1.1.7) with acetylthiocholine substrate and sulfonyl fluoride inhibitors revealed several differences between these enzymes. The fish brain AChE had a K m of 250 μM while the mammalian brain AChE had a K m of 55 μM under the same assay conditions. In addition, the mammalian brain enzyme reacted with methanesulfonyl fluoride at more than three times the rate at which the fish enzyme reacted, and fish AChE did not react with phenylmethanesulfonyl fluoride at a measurable rate while mammalian AChE was found to react rapidly. Leptocurares were found to accelerate methanesulfonylation of both enzymes; however, they inhibited phenylmethanesulfonylation. These results suggest that fish and mammalian AChE may have topographic differences in the vicinity of the anionic portion of the active site.

Quantitative studies on the water decomposition product of ethereal blue perchromate by ion-exchange resins.

Ion-exchange resins have been employed to separate Cr (III) and Cr (VI) present in the water decomposition product of ethereal blue perchromate prepared with 5-Sulphosalicylic acid. The quantitative estimations of Cr (III) and Cr (VI) present in cationic and anionic portions of the decomposition product have been determined by the usual Volumetric and Gravimetric methods. The experimental results and ratios between Cr (III) and Cr (VI) are in agreement with formula (CrIIISu)3[CrIII(CrVI2O7)3] for the water decomposition product corresponding to parent blue perchromate, (CrIIISu)3[CrIII(CrVI2O103], where Su is bivalent Sulphosalicylate ion.

Analysis for chromium traces in the aquatic ecosystem II. A study of Cr(III) and Cr(VI) in the susquehanna river basin of New York and Pennsylvania

A new procedure for the differential analysis of ppb concentrations of Cr(III) and Cr(VI) in natural waters has been developed. In this method, three-liter samples are filtered, acidified to pH 6.0, and divided into three parts. One liter is passed through an anion-exchange resin bed (AG-1X4, 100–200 mesh, Cl − form), one liter is passed through a cation-exchange resin bed (50 WX4, 100–200 mesh, Na + form), and one liter remains untreated. 10 ml of 1.0 M HNO 3 are then added to each of the three aliquots and they are individually reduced in volume by evaporation to 10 ml. Analysis by A.A. employing the method of standard addition follows. By difference, cationic, anionic, and non-ionic Cr concentrations in the sample become available. Cr(III) concentration is probably closely related to (cationic + non-ionic), and Cr(VI) concentration in the original sample corresponds to the anionic portion. Precision is ±20 % or better for total, cationic, and anionic Cr at the 1 ppb level. Precision of the non-ionic analyses is closely linked to these other precisions as the concentration of non-ionic Cr species in the original sample is obtained by the mass balance requirement set up by the other three analyses. Application of this technique to the analysis of natural water samples revealed the predominance of trivalent Cr in uncontaminated waters of the Upper Susquehanna River Basin (1–2 ppb). River water samples taken downstream of Binghamton, N.Y. area sewage outfalls revealed an increase in the mean Cr(VI) content of the river from ∼0.5 ppb to ∼1.6 ppb. The persistence of the Cr(VI) at least as far as 60 km downstream of the outfall area leads to the conclusion that at these levels, little dissolved Cr(VI) is removed from the river as it flows away from a point of contamination. Concentrations of Cr in samples of river sediments also revealed Cr contamination below the outfall area, and Cr contamination extended at least as far as 60 km downstream of the outfall area.

The Physics of Fine-Particle Movement Through Permeable Aquifers

Abstract The movement of fine particles through porous, permeable materials is closely interwoven with the migration of soluble ions. Since either the particles orthe ions can represent an economic mineral accumulation as a consequence ofgeochemical concentration, it is of great importance to mineral explorationefforts to be able to establish the parameters that influence particulatemigration through aquifers. Not only are economically interesting depositsformed by such migration, but they also may be ruined, as in the case of manyoil fields where standard secondary recovery methods have caused plugging ofthe productive formations. Recent experimental work has shown close alliance between the relative movement of both trace ions and particles and the over-all concentration of common salts dissolved in ground water. Most importantly, the spacial stability of fineparticles such as the sesquioxides and the clays in formations is dependent onthe nature of the anionic portion of the dominant salt in solution. These results have great potential, applied in exploration or exploitation programs for minerals. Not only do they provide answers for particulate migration problems in the oil fields and ore concentration mechanisms in the uranium deposits, but also they explain the untoward migration of certain radioisotopes from waste storage ponds or cribs at the national reactor-fuel reprocessing plants. By careful development and engineering practice, fine particles tagged with almost any radioactive or activatable ions may become one of the most useful tools in tracing subsurface movement of fluids. Introduction Considerable concern has been expressed by several industries during the past several decades about the effects of fine-particulate matter suspended in water passing through permeable rock. An early concern of the petroleum industry included the problem of subsurface reservoir plugging by fine particles during secondary production operations. More recently, the atomic energy industry has been concerned with particulate migration because of the movement of radioactive ions. Even the interest in applications of nuclear explosions underground has included concern over the effects of the fine-particulate matter that makes up large portions of the rubble produced by the explosion.

Electrical Conductance Study of Na+ Ion Mobility in Silicogermanate, Aluminogermanate, and Aluminosilicate Melts

Correlations between Na+ ion mobility, as determined by electrical conductance measurements, and structure changes were examined for ternary oxide melts between 1100° and 1700°C. Positive A and negative deviations for silicogermanate melts, as well as negative Λ and positive deviations for high silica or germania content melts with , can be related to (a) the oxygen packing around the Na+ ion, and (b) the local electroneutrality requirements (Na+ remains near portion of anions). Specific differences between the latter melts appear to be related to structural dissimilarities. The cation mobility increase that accompanies the gradual substitution of equimolar amounts of and for either or suggests the formation of more open, cristobalite‐like liquids as the 1/1/2 composition is approached in each system. Similarities between glass and melt conductance phenomena are also discussed.

Dinitrophenylation and inactivation of bovine pancreatic ribonuclease A

The dinitrophenylation of bovine pancreatic ribonuclease A at pH 8.0, 15 °C is confined in its initial stages to the modification of lysine residues. The sites of attack are the α-amino group of the N-terminal lysine residue and the ϵ-amino groups of the lysine residues in positions 7 and 41. The most reactive amino group is that at position 41; it reacts with fluorodinitrobenzene about 70 times faster than the ϵ-amino group in glycyl- l-lysine. Substitutions at positions 1 and 41 appear to take place independently. However, examination of the product distribution reveals that substitution at position 7 is dependent on prior reaction at position 41. This implicates a rearrangement of the tertiary structure after reaction at that position. The 41-DNP-ribonuclease A is inactive, whereas modification of the α-amino group gives rise to a product with 60% of the specific activity of ribonuclease A. The rate of the inactivation reaction is strongly affected by competitive inhibitors of the enzyme, including ortho-phosphate ion, pyrimidine nucleosides, and both pyrimidine and purine nucleotides. The results are interpreted in terms of a hypothesis which regards the ϵ-amino group of the lysine residue in position 41 as associated with a positively charged site necessary for the binding of the anionic portion of the substrate and which provides a partial explanation for the enhanced reactivity of the amino group towards fluorodinitrobenzene.

Antibiotic Potentiation: I. Influence of Anions and Fatty Substances in Lowering Calcium Inhibition of Intestinal Antibiotic Absorption by Chickens

EISNER et al. (1953) and Gray et al. (1954) demonstrated that certain organic acids and their salts enhanced absorption of tetracycline antibiotics from the gastrointestinal tract of rats, guinea pigs and dogs. It was later shown that this phenomenon was due to a reversal of calcium inhibition of intestinal absorption of the antibiotics by the organic acids (Price et al., 1959a). The effect of dietary calcium content upon serum antibiotic levels in chickens has been elucidated by Price et al. (1959b).The present report concerns experiments on factors which modify the inhibiting effect of calcium upon absorption of oxytetracycline44Terramycin, Chas. Pfizer & Co., Inc. (OTC) from the intestine of chickens. These include calcium level per se and differences related to the anionic portion of calcium salts. An exploratory study was made of possible antibiotic potentiating action of certain fatty acids, their calcium salts and natural and modified neutral fats. EXPERIMENTALExperiment 1. This experiment …

Anion inhibition of alpha-glycerophosphate dehydrogenase.

RABBIT-muscle α-glycerophosphate dehydrogenase, which catalyses the reaction: was first crystallized by Baranowski1. More recently, Beisenherz et al. 2 and Young and Pace3 have reported work in which this enzyme was studied with respect to a number of physical and chemical properties. In all cases where the above reaction was studied by measuring the reduction of dihydroxyacetone phosphate, this substrate had been prepared enzymatically4. In connexion with work on the metabolism of acetol phosphate (monohydroxyacetone phosphate)5, dihydroxyacetone phosphate was prepared by the procedure described by Ballou and Fischer6 and it was used in the experiments reported here. It was observed that dialysis of solutions of α-glycerophosphate dehydrogenase—which contained ammonium sulphate during preparation by the published procedure2—resulted in an appreciable loss of activity in some fractions (details of these experiments will be published elsewhere). Activities were determined by the spectrophotometric method of Beisenherz et al. 2. When ammonium sulphate was added back to the previously dialysed enzyme, a strong diminution of activity was noted as compared to activity of dialysed enzyme to which no ammonium sulphate was added. It was established, by comparing the effect of the corresponding sodium and potassium salts on the enzymatic activity, that this inhibitory effect was due to the anionic portion of the ammonium sulphate molecule. In addition, the ammonium, sodium and potassium salts of hydrochloric acid and the ammonium and sodium salts of formic and sulphurous acids were tested for an inhibitory effect.

REACTIONS OF ARYLSULPHONIC ESTERS: III. ON THE HYDROLYSIS OF METHYL p-METHYLBENZENESULPHONATE

A study of the temperature dependence for the rate of hydrolysis of methyl p-methylbenzenesulphonate shows the specific heat of activation for this reaction in water to be 33.45 ± 3 cal./mole degree. A comparison with the corresponding term for other methyl compounds reveals differences apparently characteristic of the anionic portion of the molecule. These differences are discussed in terms of specific solvation.