Enzyme-polyelectrolyte complex: Salt effects on the reaction of urease with polyallylamine

The effects of inorganic mono- and divalent salts of different types on how the cation polyelectrolyte polyallylamine hydrochloride (PAA) binds with the oligomer enzyme urease were studied. It was shown that in solutions of the monovalent salts NaCl, KCl, and NH₄Cl, polyelectrolyte-protein complexes formed by electrostatic interactions, which decreased monotonically as the salt concentrations increased according to the classic law of statistical physics, correlating the Debye radius with the ionic strength of the solution. In solutions of the divalent salts Na₂SO₄ and (NH₄)2_SO₄, the efficiency of the formation of the polyelectrolyte-protein complexes changed abruptly (the enzyme was drastically activated) at low salt concentrations (∼0.6–0.8 mM), which was not consistent with the classic theory of charge interactions in solutions with different ionic strengths. Turbidimetric titration at different salt concentrations in the given range revealed a high aggregative ability for sulfates and low ability for chlorides. It was concluded that the anomalies in the concentration dependence of the enzyme activity and aggregative ability were related to the formation of stable bonds PAA to the divalent SO₄²⁻ anion, which increased drastically when the ratio of anion concentration to the number of positively charged PAA monomers in solution reached 1: 2.     

Reactions of Small Aggregates of Taurine Conjugates of Dihydroxy Bile Salts with Divalent Transition Metal Ions

Formation of slightly soluble complexes between the small aggregates (dimers to tetramers) of bile salts and divalent cations, Cu²⁺, Cd²⁺, and Fe²⁺(Me²⁺), have been studied using polarography to determine concentration of free aquo ions. Polarography has been proved to be useful for studying heterogeneous equilibria. Whereas taurocholate does not form such complexes (possibly because it does not form small aggregates), taurodeoxycholate, taurochenodeoxycholate, and tauroursodeoxycholate (all bearing two OH groups) participate in formation of such complexes. Nevertheless, these complexes are much weaker than those formed with parent, unconjugated bile salts. These differences can be due to differences in stacking as well as to exchange of COO⁻for the less complex-forming SO₃⁻. The stability of complexes were characterized by values of pK_i, obtained from shifts of half-wave potentials with concentrations of bile salt in excess. The values of pK_j, corresponding to equilibria between Me²⁺in solution and solids, which can be obtained from decrease of limiting currents with concentration of bile salt, are less suitable for comparison, as it is often not possible to reach sufficiently high concentrations of bile salts. Comparison of pK_iwith pK_jindicates that for some bile salts–Me²⁺combinations the same complex predominates in solution and in the solid; for others the composition of these complexes differ. For Cu²⁺and Cd²⁺, tauroursodeoxycholate forms the most stable complexes. For all three bile salts studied, Cu²⁺formed the least stable complexes. Possibility and consequences of formation of complexes of bile salts with Me²⁺ions in bile should be kept in mind.     

NMR studies of interionic interactions in N-methylformamide

The NMR chemical shifts of alkali and thallium(I) salts with various monovalent anions have been measured in N-methylformamide solution. Lithium-7 chemical shifts are virtually concentration and counter-ion independent, presumably due to an absence of direct cation-anion interactions. The sodium-23, potassium-39 and cesium-133 chemical shifts of the salts studied depend on the anion and vary linearly with the concentration. The observed behavior can be accounted for by the formation of collisional ion pairs. On the other hand, the thallium-205 chemical shifts of thallium(I) nitrate and perchlorate were anion-dependent and varied non-linearly with the salt concentration. These results are indicative of contact ion pair formation; formation constants were calculated to be 2.6±0.4 M ^–1 for TlNO ₃ and 1.7±0.5 M ^–1 for TlClO ₄ . The cesium-133 NMR spectra of several mixed electrolyte systems also have been measured in N-methylformamide solution. The¹³³Cs chemical shifts also change linearly with the concentrations of the salts added to 0.10 M CsI/NMF solutions. The influence of the anions on the chemical shifts is the same as that observed for cesium salts alone.     

A comparative study on aqualuminescence,chemical effects and photoannealing of γ-irradiated NaCl and K2SO4

Dissolution of -irradiated sodium chloride and potassium sulphate powders in pure water and aqueous sodium nitrate solution results in the emission of light in the former, and the formation of nitrite in the latter case. Appropriate mechanisms have been suggested for the luminescence and NO ₂ ^– formation in the light of the known radiolytic products formed in the salts during the irradiation. The photoannealing of the irradiated sodium chloride under the influence of visible light and K₂SO₄ by visible ultraviolet and laser lights has been studied by monitoring the changes in the NO ₂ ^– yield with annealing times. The observed changes in the nitrite yields have been correlated with the bleaching of the radiolytic products during the photoannealing of these salts.     

Study on the synergic extraction of uranium(VI) with petroleum sulfoxides (PSO) and tri-n-butyl phosphate (TBP) mixture

The synergic extraction of uranium(VI) from nitric acid solution with petroleum sulfoxides (PSO) and tri-n-butyl phosphate (TBP) mixture has been studied. It has been found that maximum synergic extraction effect occurs if the molar ratio of PSO to TBP is two to three. The composition of the complex of synergic extraction is UO₂(NO₃)₂·TBP·PSO. The formation constant of the complex isK _PT=8.19. The effect of extractant concentration, nitric acid concentration, salting-out agent concentration and temperature on the extraction equilibrium of uranium(VI) was also studied.     

Interaction of iodine species with glycogen at high concentrations of iodine

Glycogen–iodine (GI) complex formation has been studied at different concentrations of iodine and glycogen. For each glycogen concentration (0.25, 0.125, 0.0625, 0.0313 g/L), the iodine concentration was varied from 0.0317 to 1.59 g/L and the absorbance readings were taken at 453 and 560 nm (GI wavelengths of maximum absorbance). The 453 nm absorbance curves for the GI solution (GI complex and unreacted iodine), and that of the pure iodine solution (without glycogen) level off at a high iodine concentration, and give a peak in the subtracted curve. The 560 nm curves consistently increase in absorbance, and no peak is noticed in the subtracted curve. The spectra of concentrated iodine solutions in water and alcohol suggest the formation of neutral iodine clusters. We suggest that these iodine clusters do not react with glycogen, and that the GI complex formation takes place by the addition of I₂ molecules. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35: 927–931, 1997     

Determination of vitamin B6 (pyridoxine hydrochloride) based on a novel BZ oscillating reaction system catalyzed by a macrocyclic complex

This paper reports a new method for determination of VB₆ (pyridoxine hydrochloride) by its perturbation effects on a novel Belousov-Zhabotinskii (BZ) oscillating system. This novel BZ system, in which malic acid serves as the substrate, contains an enzyme-like complex, macrocyclic complex {[CuL](ClO₄)₂}, as catalyst. The ligand L in the complex is 5,7,7,12,14,14-hexamethyl-1,4,8,11-tetraazacyclotetradeca-4,11-diene. Results show that the addition of pyridoxine hydrochloride can perturb the oscillation amplitude and period, and the change of the oscillation amplitude is linearly proportional to the concentration of pyridoxine hydrochloride in the range of 5×10^?7?2.5×10^?4 M. The obtained RSD with seven samples is 3.073%. An assay of pharmaceutical tablets of vitamin B₆ was evaluated. Some foreign ions were studied with respect to their possible influence on the determination of pyridoxine hydrochloride. The factors which influence this reaction include the concentration of reactant, the temperature of the reaction, property of catalyst, etc. Furthermore, the possible reaction mechanism has been proposed using the Field-Körös-Noyes (FKN) model.      

Dehydrochlorination of Poly(vinyl Chloride) in Pyridine. 1. Effect of Conditions

Poly(viny1 chloride) (PVC) was dehydrochlorinated thermally in pyridine solution under N₂ atmosphere and the effect of variation of reaction time, temperature, and concentration of PVC in pyridine was studied. The extent of dehydrochlorination (or conversion, x%) increases with an increase in reaction time and temperature, and with a decrease in the concentration of PVC. Incomplete precipitation of dehydrochlorinated PVC (DHPVC) occurs by nonsolvent (methanol). During dehydrochlorination there is no HCl evolution as it forms a pyridine hydrochloride complex which is supposed to act as a catalyst for dehydrochlorination. A possible mechanism has been proposed. Chain scission and cross-linking reactions are responsible for the molecular weight changes that take place during the reaction.     

Concentration of potassium cations in the permeate solution in the presence of N,N-dimethyl-N-2-propenyl-2-propen-1-aminium chloride homopolymer using dead-end nano-or ultrafiltration

The investigation is based on the nano-or ultrafiltration of inorganic salts in the presence of a polyelectrolyte in the feed solution. Cellulose acetate membranes are selected with a pore size of 10–20 nm. The membranes are imaged using atomic force microscope. The membrane is completely impermeable to the polyelectrolyte. Polyelectrolyte concentrations are taken in the range of 0.5–1 g/l to avoid a gel layer formation over the membrane. It is discovered that, at such low polyelectrolyte concentration, inorganic salt concentration in the permeate is higher than in the feed solution. This process therefore deviates from conventional membrane separation processes, where the permeate salt concentration is lower or equal to the salt concentration in the feed solution. It is shown that during the nano-or ultrafiltration of inorganic salts in the presence of polyelectrolyte, the ratio of salt concentration in the permeate to feed increases when the initial salt concentration in the feed solution is low. Concentration polarization has a negative impact on this concentrating effect. In the case of this investigation, KCl, KNO₃, K₂SO₄ are taken as inorganic salts, N,N-dimethyl-N-2-propenyl-2-propen-1-aminium chloride homopolymer is selected as a polyelectrolyte. The text was submitted by the authors in English.     

Study of Capah Membranetropic Action on the Artificial Biomembranes

Abstract

The drugs neurotropic effects are known to be connected with their ability to change the physicochemical parameters of membrane organisation. Having been investigated last time, phosphorylacetic acid hydrazides R(R')P(O)CH₂C(O)NHNH₂ display neuroprotective, memory enhancing and antidepressive acttvities. The lead representative of these series is CAPAH (I)(R=Me₂,NC₆H₄; R'=CIC₂H₄O) We have now studied these compounds influence on the organization of model phospholipid membranes from egg yolk phosphatidilcholine (PC) ³¹P NMR technique was applied as particularly useful analytical tool for he study of the polymorphic phase behavior of hydrated phospholipids. The main feature of the CAPAH effect on ³¹P NMR spectra consists of an appearance of narrow symmetrical signal indicatingeffectively isotropic motion of the phospholipid molecules. PHOSENAZID (II) (R=R'=C₆H₅) renders the similar action on the membranes. It is confirmed by earlier obtamed Infrared spectroscopy data that showed the formation of intermolecular hydrogen bond between carbonyl groupof phospholipid molecule and hydrazide fragment of CAPAH^|2|. N-acyl derivative of CAPAH (III) did not affect the PC liposomes. Using of CAPAH and PHOSENAZID hydrochloride salts (IV.V) causes more drastic changes in the bilayer structure of liposomes apparently in the consequence of the additional interaction of salt anion with positive charged PC choline fragment. The results obtained are inan agreement with the preliminary studies of antioxidant effect of these compounds in vitro. Thus, the hydrochloride salts (IV, V) possess more marked influence on lipid peroxidation process in membranes of rat brain, and all tested hydrazides form the line increasing antioxidant activity (III)→ (11)→ (I)=(V)→ (Vl).     

Investigations of the use of 4-(5-nonyl)pyridine as a liquid anion exchanger for tetrachloroferrate ions in aqueous chloride media

In an attempt to gain an understanding of factors affecting the extraction of iron(III) by 4-(5-nonyl)pyridine, the equilibria between hydrogen chloride and benzene solutions of 4-(5-nonyl)pyridine have been studied. From acid distribution data and visible absorption spectra of the organic phases, it was concluded that FeCl ₄ ⁻ ion, with a tetrahedral sp³ configuration is the principal iron containing species. The pyridine extraction of macro and trace amounts of the metal has indicated the formation of 1∶1 and 2∶1 complexes respectively. The 2∶1 complexes are assumed to result from association of a 1∶1 complex with a molecule of the pyridine hydrochloride. The salting-out effect increases in the order, LiCl<NaCl<MgCl₂<AlCl₃ and these differences in the effect have been attributed to the different degree of hydration of cations of the salts present and to the ionic radii. The effect of various anions including the reducing agents have been described. Separation factors of several metal ions relative to ferric iron, in 6M HCl, are also reported.     

Influence of transitional metal ions on lyotropic liquid crystals of hydroxyethyl cellulose acetate in N,N-dimethylformamide

The influence of inorganic salts on the formation of lyotropic liquid crystals of hydroxyethyl cellulose acetate (HECA) in N,N′dimethylformamide (DMF) was studied. In the presence of CaCl₂, an inorganic salt of a principal group metal, the solution of HECA/DMF/CaCl₂ was a biphasic system. The temperature of the transformation from the liquid crystalline phase to the isotropic one increased with adding CaCl₂ because local HECA concentration increases in the HECA/DMF phase. When CuCl₂ or CoCl₂, inorganic salts of transitional metals, was added, the solutions were monophasic systems and the complexes of HECA with Cu²⁺ or Co²⁺ were formed in solutions, which results in the increase of the temperature of the transfomation from the liquid crystalline phase to the isotropic one.     

Studies in cluster ion formation. Part I. Fast atom bombardment mass spectrometry of tetraalkylammonium halides: Factors influencing cluster ion size and stability

Positive and negative ion fast atom bombardment mass spectra of tetraalkylammonium halide salts (NR₄X, where X = Cl, Br, I and NR₄ = NMe₄, NEt₄) have been studied and intense cluster ion formation has been observed. The cluster ion intensity distributions were found to show enhancements at certain cluster numbers (n). The negative cluster ions of NMe₄X salts showed anomalous ion intensity regions, which differed from both the positive cluster ions of all NR₄X salts and also the corresponding negative clusters of NEt₄X salts. The influence of anion and cation size on cluster ion formation and abundances has been studied and it has been established that smaller anion and cation size favours the formation of larger cluster ions. The possible structures of the cluster ions exhibiting relative increased stabilities are discussed.     

Investigation and radiometric determination of saturated and unsaturated aliphatic monocarboxylic acids and aromatic dicarboxylic acids

Investigations have been carried out on the precipitation of calcium salts of saturated and unsaturated aliphatic monocarboxylic acids and of aromatic dicarboxylic acids. The optimum ethanol/water solvent ratio has been studied at which the sodium, ammonium or triethylammonium salts of the acids have a good solubility, whereas the calcium salts are poorly soluble and can be precipitated. Based on these investigations the radiometric determination of formic acid, palmitic acid, stearic acid, methacrylic acid, oleic acid, and o-, m- and p-phthalic acids has become possible. A linear correlation has been found between the solubilities of the calcium salts of o-, m- and p-phthalic acids and the dielectric constant of the solvent mixture. CaCl₂ solution labelled with⁴⁵CaCl₂ was used for the titrations, with a solvent composition identical to that of the solution to be titrated. Radiometric titrations were carried out in 0.05M solutions for dicarboxylic acids, and in 0.1M solutions for monocarboxylic acids. For palmitic and stearic acids titrations were also carried out in the 0.01M concentration range. The equipment used for titrations was capable of detecting isotopes of soft β-radiation.     

Kinetics of precipitation and growth of thin indium(III) sulfide films

Thin films of indium(III) sulfide have been prepared by chemical precipitation from aqueous solutions containing indium(III) nitrate, thioacetamide, tartaric acid, and hydroxylamine hydrochloride at 333–368 K. Kinetics of In₂S₃ precipitation and the films growth under conditions of spontaneous formation of the solid phase in the solution has been studied. Formal rate law of indium(III) sulfide formation accounting for the partial orders of In₂S₃ precipitation with respect to the system components and the process activation energy has been derived. The effects of the reaction mixture composition, temperature, and the synthesis duration of In2S3 films growth have been studied.     

Unwinding of ι-carrageenan double helix upon complex formation with polyethylaminophosphazene hydrochloride

The interaction of poly(ethylaminophosphazene) hydrochloride (M _SD = 3.2 × 10⁵) with potassium ι-carrageenan (M _w = 2.2 × 10⁵), which is a linear regular anionic polysaccharide, has been studied by high-sensitivity DSC at pH 3.8 in a 0.15 mol/l solution of KCl. The dependences of temperature, enthalpy, and the cooperativity parameter of the double helix-coil transition of polysaccharide on the concentration ratio of polyphosphazene and polysaccharide have been obtained. The presence of polyphosphazene has no effect on the temperature and cooperativity of transition, whereas the enthalpy of the transition decreases linearly with the content of polyphosphazene and turns to zero at a mass polymer-to-polysaccharide ratio of approximately 1: 1, which corresponds to the equivalent concentrations of polyphosphazene and polysaccharide with respect to charges. Our data indicate that the mixing of poly(ethylaminophosphazene) hydrochloride and potassium ι-carrageenan solutions gives rise to formation of the stoichiometric interpolyelectrolyte complex, in which the polysaccharide loses its ability to form double helix typical of ι-carrageenan in saline solution (0.15 M KCl).     

Rearrangement of 2-hetarylalkylpyridinium salts

The rearrangement of 2-thienyl- and 2-furylalkylpyridinium salts to the corresponding anilines by the action of methylammonium sulfites has been studied. It has been shown that the rearrangement of these salts is accompanied in many cases by the formation of phenols and dealkylation products. The influence of the length of the alkyl chain between the heterocyclic rings on the ratio of the rearrangement products has been investigated.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 3, pp. 368–371, March, 1986.     

Effect of electrolytes on the cloud point of chlorpromazine hydrochloride solutions

Cloud point (CP) phenomenon occurring in amphiphilic drug chlorpromazine hydrochloride (CPZ) solutions with and without salts is reported herein. The CP of a 50mM CPZ solution (prepared in 10mM sodium phosphate, SP, buffer) was found to decrease with increasing pH, both in the absence as well as presence (50mM) of added salts (NaCl, NaBr, LiBr, KBr, tetra-n-butylammonium bromide). Whereas, at a fixed concentration of NaCl, the CP increased with increasing CPZ concentration, addition of increasing amounts of salts (NaF, NaCl, NaBr, LiCl, KCl) to 50mM CPZ solution (at pH 6.7) caused continuous increase in CP. On the basis of these studies the binding-effect orders of counterions and co-ions have been deduced, respectively, as: Br(-)>Cl(-)>F(-) and Li(+)>Na(+)>K(+). The similar trend of increasing CP with addition of increasing amounts of quaternary bromides (tetramethylammonium bromide, TMeAB; tetraethylammonium bromide, TEtAB; tetra-n-propylammonium bromide, TPrAB; tetra-n-butylammonium bromide, TBuAB; tetra-n-pentylammonium bromide, TPeAB) to 50mM CPZ solutions (at pH 6.7) was found to be dependent upon the alkyl chain length of the particular salt. The overall behaviour has been discussed in terms of electrostatic interactions, micellar growth, and mixed micelle formation.     

Use of some new chelating agents for the colorimetric determination of iron: Ethylenediamine-bis-sulphosalicylaldehyde

Ethylenediamine-bis-sulphosalicylaldehyde, which gives strong violet-red coloration with. ferric salts owing to the formation of a stable metal chelate complex, Fe(C₈H₉O₄NS)Cl.H₂O, has been utilized for the colorimetric determination of ferric iron, using a Hilger-Spekker photoelectric absorptiomcter. The maximum intensity of absorption occurs at pH 2.8–5.5 in the green region (510–520 mμ) of the visible spectrum.The colour complex has been found to obey Beer's law between 0.25 and 10 p.p.m. The influences of several foreign, ions on the reaction have been carefully studied. The metal chelate complex has been isolated and its properties studied.     

Monomer-catalyst complexes in the stereospecific polymerization of aliphatic aldehyde. The structure and chemical behavior of the aldehyde complex of [R2AlOCR′NPh]2

The reaction between some aliphatic aldehydes (acetaldehyde, propionaldehyde and butyraldehyde) and the typical stereospecific polymerization catalyst R₂AlOCR′NPh has been studied in an attempt to elucidate the initiation mechanism of the polymerization reaction. The monomer-catalyst (1/1) complexes obtained from these aldehydes and R₂AlOCR′NPh possess excellent catalytic activity towards the stereospecific polymerization. The structure of the complex in solution has been determined by NMR and IR spectra and compared with the structure determined by X-ray structure analysis. The presence of pentacoordinate aluminum in the complex has been demonstrated, for the first time, by X-ray studies.The structure of the aromatic monoaldehyde complex has also been studied and shown to be identical with that of the aliphatic aldehyde complex mentioned above. The chemical behavior of these aldehyde complexes towards Lewis bases and Lewis acids has also been studied. The aldehyde moiety of the R₂AlOCR′NPh - MeCHO complex is liberated by the action of a strong Lewis base such as trimethylamine oxide and hexamethylphosphoramide, and is easily exchanged for another kind of aldehyde. The trimethylaluminum complex, Me₂AlOCPhNPh · MeCHO · AlMe₃, which only leads to the formation of amorphous polyacetaldehyde in contrast to Me₂AlOCPhNPh · MeCHO, has been isolated and its structure determined by IR, NMR and X-ray studies in order to establish the relationship between its structure and its chemical behavior.