EFFECT OF ELECTROLYTES ON ELECTROSURFACE PROPERTIES OF MICROCRYSTALLINE CELLU-LOSE PARTICLES

The electrical surface properties (specific surface charge of particles - σ0, point of zero charge – pHPZC, electrokinetic potential - ζ and position of isoelectric point - pHIEP) of dispersions of microcrystalline cellulose (MCC) in aqueous solutions of H2SO4, NaOH, Na2SO4 and TiOSO4 were investigated. Significant effects of specific adsorption of anions and cations on pHPZC and pHIEP have been demonstrated. The isoelectric point of the MCC particles in the H2SO4 solution is at pH 2.0, while the zero charge point in 5·10-4 M solution Na2SO4 at pH 5.6. An explanation of the observed effects is given. Possible schemes of the structure of the electrical double layer at different pH values, taking into account specific adsorption of ions in the Stern layer, are given. The introduction of TiOSO4 (10-5 mol/dm3) shifts the position of IEP to a less acidic region (pHIEP 4.5) due to the specific adsorption of positively charged TiOSO4 hydrolysis products particles.

BUFFER SYSTEMS BASED ON AMINOMETANESULPHONATE AND MONOETHANOLAMMONIUM N-ALKYLAMINOMETHANESULPHONATES

The limits of the pH buffering action (pHbuff) of YNHCH2SO3H – NH2CH2CH2OH –H2O (Y = H, CH3, HOCH2CH2, t-С4H9 and C6H5CH2) were determined and their buffer capacity (p) for monoethanolamine (MEA) was estimated in the temperature range 293–313 K. For systems with aminomethanesulfonic acid (AMSA), its N‑methyl, N‑hydroxyethyl (HEAMSA) and N‑benzyl (BzAMSA) derivatives, an increase in temperature leads to a decrease in the pH values of the lower limit of the buffering action of their solutions with monoethanolamine; in the case of N‑tert-butylaminomethanesulfonic acid (t-BuAMSA) – to an increase in the specified characteristic. An increase in temperature for systems with the most hydrophobic t-BuAMSA and BzAMSA (in comparison with other studied aminomethanesulfonic acids) leads to a decrease in the pH values of the upper limit of the buffer action. A decrease in the YNHCH2SO3H and NH2CH2CH2OH concentration leads to a shift in the boundaries of the pH of the buffering action to a more acidic region. The nature of the influence of the empirical function, combining their acid-base properties and lipophilicity (рKа + lgPow), on the concentration dependence of the buffer capacity according to MEA was revealed. It is shown that the buffering effect of the studied systems is due to the presence, in addition to the systems N‑alkylammoniummethanesulfonate – N‑alkylaminomethanesulfonate and 2-hydroxyethylammonium – monoethanolamine, ionic associates (pairs and triples). The position of the extrema on the graphical π=f(CMEA)/QYAMSA) dependencies for systems with hydrophilic AMSA and HEAMSA coincides with the position of the first minima on the differential titration curves dpH/dV = f(CMEA)/QYAMSA). Substitution of MEA to potassium aminomethanesulfonate leads to a shift in the pH buffering action to a more acidic region and increases the buffer capacity of the resulting systems.

Effect of Digestate from Rubber Processing Effluent on Soil Properties

Anaerobic digestion of rubber processing effluent (RPE) was conducted at 1:1 Effluent to Inoculums ratio to obtain biogas at a 40–day retention time. The physicochemical properties of the RPE were determined before and after anaerobic digestion. Digestate obtained thereof was used as soil amendment to investigate its bio-fertility potential. To study the effects, three kilograms (3Kg) of soil samples were separately treated with 0, 200, 400, 600 of the digested RPE. The effluent applied were thoroughly mixed with the soil, watered regularly and left for eight weeks for adequate mineralisation and equilibration. The soil physicochemical properties were determined before and after the amendment. The results from the amended soils showed that application of the digestate enhanced soil quality (as soil organic carbon, N, P, K, Ca, Na and % base saturation were significantly higher than in the control). However, the soil pH remained in the acidic region and the soil exchangeable acidity reduced. Keywords: Digestate, soil properties, biogas, RPE.

Acidic Region Residues 1680–1684 in the A3 Domain of Factor VIII Contain a Thrombin-Interactive Site Responsible for Proteolytic Cleavage at Arg1689

Factor VIII (FVIII) is activated by thrombin-catalyzed cleavage at Arg372, Arg740, and Arg1689. Our previous studies suggested that thrombin interacted with the FVIII C2 domain specific for cleavage at Arg1689. An alternative report demonstrated, however, that a recombinant (r)FVIII mutant lacking the C2 domain retained >50% cofactor activity, indicating the presence of other thrombin-interactive site(s) associated with cleavage at Arg1689. We have focused, therefore, on the A3 acidic region of FVIII, similar to the hirugen sequence specific for thrombin interaction (54–65 residues). Two synthetic peptides, spanning residues 1659–1669 with sulfated Tyr1664 and residues 1675–1685 with sulfated Try1680, inhibited thrombin-catalyzed FVIII activation and cleavage at Arg1689. Treatment with 1-ethyl-3-(3-dimethylaminopropyl)-carbodiimide to cross-link thrombin with either peptide showed possible contributions of both 1664–1666 and 1683–1684 residues for thrombin interaction. Thrombin-catalyzed activation and cleavage at Arg1689 in the alanine-substituted rFVIII mutants within 1663–1666 residues were similar to those of wild type (WT). Similar studies of 1680–1684 residues, however, demonstrated that activation and cleavage by thrombin of the FVIII mutant with Y1680A or D1683A/E1684A, in particular, were severely or moderately reduced to 20 to 30% or 60 to 70% of WT, respectively. Surface plasmon resonance-based analysis revealed that thrombin interacted with both Y1680A and D1683A/E1684A mutants with approximately sixfold weaker affinities of WT. Cleavage at Arg1689 in the isolated light-chain fragments from both mutants was similarly depressed, independently of the heavy-chain subunit. In conclusion, the 1680–1684 residues containing sulfated Tyr1680 in the A3 acidic region also contribute to a thrombin-interactive site responsible for FVIII activation through cleavage at Arg1689.

Determination of the Conditions for Agglomeration of Molybdenite Fines in the Presence of Kerosene Emulsion Through the Extended DVLO Theory

The hydrophobic agglomeration of fine particles of molybdenite in the presence of kerosene emulsion, has been studied in this paper. The results obtained in the investigation as; zeta potential of kerosene emulsion(ζemulsion), zeta potential of the molybdenite sample (ζMoS2), hydrophobicity of molybdenite represented by the contact angle (θMoS2) varying the pH, were used to calculate the total potential energy through the extended DVLO theory. Diagram containing curves total potential energy vs. separation distance of the particles, indicate that increasing the pH, also increases the energy barrier to overcome to achieve agglomeration and viceversa, which translates to a high probability of agglomeration in the pH range 5 to 8, with greater effect as the pH is increased in the acidic region.

OsChz1 acts as a histone chaperone in modulating chromatin organization and genome function in rice

While the yeast Chz1 acts as a specific histone-chaperone for H2A.Z, functions of CHZ-domain proteins in multicellular eukaryotes remain obscure. Here, we report on the functional characterization of OsChz1, a sole CHZ-domain protein identified in rice. OsChz1 interacts with both the canonical H2A-H2B dimer and the variant H2A.Z-H2B dimer. Within crystal structure the C-terminal region of OsChz1 binds H2A-H2B via an acidic region, pointing to a previously unknown recognition mechanism. Knockout of OsChz1 leads to multiple plant developmental defects. At genome-wide level, loss of OsChz1 causes mis-regulations of thousands of genes and broad alterations of nucleosome occupancy as well as reductions of H2A.Z-enrichment. While OsChz1 associates with chromatin regions enriched of repressive histone marks (H3K27me3 and H3K4me2), its loss does not affect the genome landscape of DNA methylation. Taken together, it is emerging that OsChz1 functions as an important H2A/H2A.Z-H2B chaperone in dynamic regulation of chromatin for higher eukaryote development.

EXTRACTION OF METAL IONS BY 4-BENZOYL- OR 4-(3-NYTROBENZOYL-1-HEXYL- 3-METHYL-2-PYRAZOLINE-5-ONES

The extraction properties of solutions of 4-benzoyl- and 4- (3-nitrobenzoyl) -1-hexyl-3-methyl-2-pyrazolin-5-ones in chloroform were studied. The pH dependence of the degree of extraction is S-shaped. Ions Cu2+, Pb2+, Zn2+, Ni2+, Co2+, Mn2+, Cd2+, Ca2+, Mg2+ are extracted in the form of complexes with the ratio M (II): reagent determined by the equilibrium shift method equals to 1: 2. A lower equilibrium pH than the initial value indicates a cation-exchange extraction mechanism. The introduction of an electronegative nitro group into the benzoyl fragment of the reagent led to a shift in the pH50 values of the extraction of metal ions in a more acidic region. The presence of a correlation between the values of the Klopman hardness parameters of the above metal cations and extraction pH50 values was shown. The influence of the nature of the solvent on the extraction of zinc ions was studied. The addition of polar isopentanol to the extractant shifts the pH of the metal extraction to a more acidic region. In order to increase the pH50 value of zinc extraction, the solvents are arranged in a row: 30% isopentanol in CHCl3 < benzene < xylene < toluene < chloroform < dichloroethane. The introduction of additional neutral electron-donating hydrophobic organic compounds into the extract: 1-hexyl-3-methyl-2-pyrazolin-5-one, triisobutyl phosphate, trioctylphosphine oxide significantly increases the values of the partition coefficients of zinc. The observed synergistic effect is explained by the formation of a coordinatively unsaturated intracomplex compound of zinc with aroylpyrazolone, in which the free coordination sites are filled with neutral reagent molecules. In this case, water is replaced and due to the increased hydrophobicity of the complex, an increase in extraction occurs. Confirmation of the formation of a coordination-unsaturated zinc complex is a close to unity value of the slope of the decimal logarithm of the metal distribution constant for pH.

COMPLEXATION OF MOLIBDENUM(VI) WITH 6,7-DIHYDROXY-4-METHYL-2-PHENYLCHROMENYLIUM AND ITS HALOGEN DERIVATIVES IN SOLUTIONS

It was determined the chemico-analytical characteristics and composition of the complexes formed in the Mo(VI)–DOCh systems. The composition of the complexes (Mo(VI):DOCh = 1:2) was found by spectrophotometric methods (molar ratios, equilibrium shift). A probable complex chemistry was proposed based on a combination of spectrophotometric and mass- spectrometric data. It was shown that the MoO22+ cation acts as a complexing agent, and the ligand enters into the reaction in the form of an anhydrobase. It was found, that halogen-containing derivatives of MPDOCh form more intensely colored and stable complexes with Mo (VI) than MPDOCh, and the optimal pH of complexation shifts to a more acidic region. The study of the complexation of molybdenum(VI) with 6,7-dihydroxy-4-methyl-2-phenylchrome-nilium (MPDOCh) and its chlorine and bromine derivatives containing a halogen atom in 4th position in phenyl ring was shown that MoO22+ cation acts as a complexing agent, and the ligand involved into reaction in the form of an anhydrobase. The analytical characteristics of the resulting complexes were determined, and it was also noted that the halogen derivatives of MPDOCh form more intensely colored and stable complexes with Mo(VI).