Some physicochemical properties of aluminum and iron chloride solutions

Some physicochemical properties of aluminum and iron chloride solutions are considered. The density and viscosity of aluminum and iron chlorides are plotted as functions of the FeCl₃/(FeCl₃ + AlCl₃) ratio and temperature, and pH of aluminum hydroxochlorides is plotted as a function of the Al₂O₃ content in a solution and its basicity (ratio of contents Al/Cl). The joint solubility of aluminum hydroxochloride and sodium chloride in water has been analyzed.     

Heparin-binding properties of selenium-containing thioredoxin reductase from HeLa cells and human lung adenocarcinoma cells

Mammalian selenocysteine-containing thioredoxin reductase (TR) isolated from HeLa cells and from human lung adenocarcinoma cells was separated into two major enzyme species by heparin-agarose affinity chromatography. The low-affinity enzyme forms that were not retained on heparin agarose showed strong crossreactivity in immunoblot assays with anti-rat liver TR polyclonal antibodies, whereas the high-affinity enzyme forms that were retained by the heparin column were not detected. Both low and high heparin-affinity enzyme forms contained FAD, were indistinguishable on SDS/PAGE analysis, and exhibited similar catalytic activities in the NADPH-dependent DTNB [5,5'-dithiobis(2-nitrobenzoate)] assay. The C-terminal amino acid sequences of 75Se-labeled tryptic peptides from lung adenocarcinoma low- and high heparin-affinity enzyme forms were identical to the predicted C-terminal sequence of human placental TR. These two determined peptide sequences were -Ser-Gly-Ala-Ser-Ile-Leu-Gln-Ala-Gly-Cys-Secys-(Gly). Occurrence of the Se-carboxymethyl derivative of radioactive selenocysteine in the position corresponding to TGA in the gene confirmed that UGA is translated as selenocysteine. The presence of cysteine followed by a reactive selenocysteine residue in this C-terminal region of the protein may explain some of the unusual properties of the mammalian TRs.     

Creation of a ribonuclease abzyme through site-directed mutagenesis

The development of abzymes (antibody/enzymes) is one method of creating reagents with novel catalytic activity. To date, most abzymes have been obtained by immunization with transition state analogs. We have chosen to start with an existing antibody and convert it into an enzyme by the addition of catalytic residues to the binding site. We have introduced a histidine residue into antibody Jel 103 and converted it into an abzyme that cleaves poly(rI) with a kinetic efficiency of about 100 M(-1) sec(-1).     

Investigation of physicochemical and technological properties of sodium tetrafluoroaluminate

Physicochemical properties of condensed sodium tetrafluoroaluminate are investigated by methods of thermogravimetry, high-temperature X-ray phase analysis, and thermodynamic calculations of the phase diagram of the NaF-AlF₃ system. It is shown that it is possible to use this compound as a correcting additive to electrolyte in aluminum electrolyzers instead of the mixture of cryolite and aluminum trifluoride. This replacement allows one to reduce the consumption of fluorine salts, to optimize the balance of production components, and to make aluminum production more environmentally friendly.     

Some biochemical aspects of the enzymic transformation of cortisol with Bacillus cereus

The role of a variety of compounds including organic acids, vitamins, growth promoting substances, purines and pyrimidines in the bioconversion of cortisol with Bacillus cereus was investigated. The transformation of cortisol to prednisolone and pregn-4-en-11beta, 17alpha,20beta, 21-tetrol-3-one was affected by these compounds in different manners. The enzymatic delta1-dehydrogenation reaction was greatly induced with fumarate, menadione, and xanthine treatments. However, the enzymic reduction of the 20-carbonyl to the 20beta-ol was specifically stimulated with fumarate, nicotinic acid amide, and uracil treatments.     

Dusting and fluidity of alumina with different physicochemical properties

The objects of investigation were metallurgical aluminas from different manufacturers and with different physicochemical properties varying in wide limits: the content of the fraction ?45 μ m was 4–60%, the losses during calcination were 0.5–1.2%, the content of the α phase was 2.5–23.0%, and the specific surface was 55–120 m²/g. The outflow time t _out of the aluminas was measured using funnels with standard (2.4 mm) and increased (4 and 5 mm) orifices; the outflow time was 2–20 min. The correlations for the values of t _out for the funnels with mentioned orifices were obtained. The outflow time decreased as the content of the fraction ?45 μ m decreased and the water content in alumina increased. The dusting factors (DF) of aluminas were measured with the help of the developed dust counter, and the variation range was 0.5–8.0 mg/g. The dusting factor increased as the content of the fraction ?45 μm and water content in aluminum increased. The main factor determining t _out and DF is the granulometric composition of alumina. The effect of the form of alumina particles and moisture content in alumina on the t _out and DF is established. The mechanism explaining the interrelation between the moisture and these values is suggested.     

Differences in physicochemical and antigenic properties of chlamydial strains

Antigenic analysis of Chlamydia psittaci, C. trachomatis, and Lymphogranuloma venereum (LGV) revealed basic physicochemical differences among the three chlamydial strains. These were manifested in structural, isoelectric points, absorption spectra, and in the characteristics of the chromophobe-containing proteins. The effective period of sonication for C. psittaci and C. trachomatis is around 60 min during which the linkages most susceptible to external sonication forces were broken, releasing all attainable cellular components. Denaturation studies demonstrated that less than 50% of protein content of C. psittaci was denatured after 1 h of sonication, only 5% in the case of C. trachomatis. The protein and carbohydrate content of the most reactive fractions in macrophage-spreading inhibition test were different for LGV and C. trachomatis. The structural differences appear to determine the antigenic properties observed among the chlamydial strains as well as the specificity and probably the mechanisms (s) of cellular immune reactivity to Chlamydiae. This in turn may explain the failure of chlamydial vaccines, prepared from stock strains, to protect immunized children against 'wild' chlamydial strains.     

Colorimetric estimation and some physicochemical properties of purified Cyanex 272

A technique for the colorimetric estimation of purified Cyanex 272 has been developed. The technique consists of the digestion of pure sample or its aqueous solution with concentrated nitric acid (70%)–perchloric acid (70%) mixture for 1 h. The oxidizing mixed acid quantitatively converts Cyanex 272 to a clear solution of orthophosphate that can be easily estimated by the molybdenum-blue colorimetric method at 830 nm. The method is sensitive with a molar extinction coefficient of ∼2.6×10⁴ and reproducible within ±2%. Applying this technique of analysis, the dimerization constant (K₂), distribution or partition coefficient (K_d) and ionization constant (K_a) of the purified Cyanex 272 (bis-2,4,4-trimethylpentylphosphinic acid, BTMPPA) have been estimated to be 190, 53 and 5.52×10⁻⁴, respectively.     

Correlation between the structures and physicochemical properties of chemotherapeutic fluoroquinolone agents

The acid-base properties, the lipophilicity and the HPLC behaviour of nine antibacterial fluoroquinolone derivatives were studied to reveal relationship between these physico-chemical parameters and the chemical structure. Basicity of compounds with two proton-binding sites is depicted here in terms of protonation macro- and microconstants. The concentrations of microspecies (cation, zwitterion, neutral and anion) were calculated in the function of pH. The microspeciation of fluoroquinolones were used to derive relationship between the apparent and true octanol/water partition coefficients. An analysis of structure-chromatographic behaviour has been performed utilizing the retention values was determined in a chromatographic system methanol-aqueous phosphate buffer/ODS. Close correlation was found between the lipophilicity and chromatographic behaviour of the tested compounds when pH dependence and the influence of an ionpairing agent were investigated.     

Relationship between the electromagnetic and physicochemical properties of carbonyl iron powder

Summary The relationship is examined between the electromagnetic properties of carbonyl iron powder and some factors involved in the manufacture of this powder. The electromagnetic properties depend on the onion skin structure of the powder particles and the chemical composition and particle size of the powder.Translated from Poroshkovaya Metallurgiya, No. 7 (43), pp. 38–44, July, 1966.     

The physicochemical properties of hair in the BIDS syndrome

The physicochemical properties of hair from a new recessive syndrome associated with brittle hair, intellectual impairment, decreased fertility, and short stature have been studied. Electrophoresis of the SCM-structural proteins showed that the alpha polypeptides appeared normal, but the matrix component was markedly reduced. This was confirmed by finding a normal alpha X-ray diffraction pattern but a reduced 1/2 cystine content of hair and an abnormal stress-strain curve. Electron-microscopic studies revealed extreme disorganization of the filaments which most likely resulted from the absence of normal cross-linking. Nails, which contain structural proteins similar to hair, also showed the abnormality. Since the matrix component seen by electrophoresis consists of more than one component the defect cannot be explained as a single structural gene abnormality.     

Effects of mechanical activation on physicochemical properties and alkaline leaching of hemimorphite

Effects of mechanical activation on physicochemical properties and alkaline leaching of hemimorphite from Lanping, Yunnan province were studied. The results showed that both dry milling and mechano-chemical milling could enhance zinc extraction rate and shorten the leaching time. Scanning electron microscope (SEM), particle size distribution (PSD), X-ray diffraction (XRD) analysis demonstrated that different milling times and modes could form different morphologies, particle size distributions and crystal structures, thus influence zinc recovery differently.     

火试金富集—原子吸收光谱法测定含硒物料中的金

研究建立了火试金富集—原子吸收光谱法测定含硒物料中金的方法。样品挥发除硒处理后经火试金法富集得到金银合粒,分金后金粒用王水溶解,且在王水介质中采用原子吸收光谱仪测定。该方法相对标准偏差为1.0%~3.3%,加入标准物质回收率为95.0%~103.5%。     

Iontophoretic transport pathways: dependence on penetrant physicochemical properties

The objective of this work was to investigate how the preferred iontophoretic transport pathways of a molecule depend on its physicochemical properties. Laser scanning confocal microscopy (LSCM) was used to visualize in hairless mouse skin the distribution of two fluorescent penetrants: calcein, a multiply charged (-4), hydrophilic molecule; and nile red, a lipophilic, neutral compound. Iontophoresis and passive delivery of nile red showed that the percutaneous transport of this compound occurred via (inter- and intracellular) pathways that were clearly distinct from those followed by calcein. Although the distribution of nile red was influenced somewhat by the passage of current relative to the passive control, there was relatively little enhancement of the penetration of this compound into the skin. Calcein, on the other hand, did not passively enter the skin. However, with iontophoresis, greatly enhanced transport, with an important contribution from follicular structures, was observed. Sequential (dual) transport of the two fluorophores illustrated clearly the different pathways followed and reflected the transport and visualization studies of the individual species. It may be concluded, therefore, that the iontophoretic pathways followed across the skin are dictated by the physicochemical properties of the penetrant and by its affinity for the different environments available.     

Effect of the physicochemical properties of molten copper on the structure and properties of the atomized powders

Translated from Poroshkovaya Metallurgiya, No. 7 (343), pp. 1–5, July, 1991.     

t-Butyl hydroperoxide-induced changes in the physicochemical properties of human erythrocytes

Treatment of human erythrocytes with micromolar concentrations of t-butyl hydroperoxide causes a variety of changes in the physical properties of the cells. Red cells exposed to concentrations of t-butyl hydroperoxide of less than 750 microM for 15 min exhibited significant decreases in cellular and membrane deformability, increases in membrane-associated protein cross-linking, osmotic fragility and the viscosity of the intracellular hemoglobin solution. No changes in the volume or density of the cells were observed. Changes in cellular deformability are probably attributable solely to changes in the mechanical properties of the cell membrane. Conversely, when red cells are exposed to t-butyl hydroperoxide concentrations in excess of 750 microM for 15 min they exhibited decreases in cellular deformability which may be related to increases in cell volume as well as membrane rigidity.     

Adhesion strength and physicochemical properties of molybdenum and tantalum coatings on titanium nickelide

The methods of estimating the adhesion strength are considered, the surface morphology is studied, and a layer-by-layer analysis is performed in the near-surface volume of titanium nickelide coated with molybdenum and tantalum films of various thicknesses. The mechanical and adhesion strengths of the coatings are shown to depend on the coating thickness and the chemical compositions of the film and substrate.     

Phosphoenolpyruvate carboxykinase from Trypanosoma cruzi. Purification and physicochemical and kinetic properties

Phospho enolpyruvate carboxykinase (PEPCK) has been purified to homogeneity from epimastigotes of the Tul 0 strain of Trypanosoma cruzi. The physicochemical parameters determined allowed the calculation of an average molecular mass of 120 kDa; the subunit molecular mass, about 61 kDa, is in good agreement with the value of 58.6 kDa recently determined from the sequence by Sommer et al. (FEBS Lett. 359 (1994) 125-129). The PEPCK from T. cruzi presented, in addition to its molecular mass, typical properties of other ATP-linked PEPCKs, namely strict specificity for ADP in the carboxylation reaction and lower specificity in the decarboxylation and exchange reactions, and synergistic activation by CdCl2 or MgCl2 when added in addition to MnCl2. The enzyme presented hysteretic behaviour, shown by a lag period in the carboxylation reaction, which was affected by dilution and preincubation. The decarboxylation reaction catalyzed by the T. cruzi PEPCK was not inhibited by excess of ATP-Mn. The apparent Km values for the carboxylation reaction, including the low value for PEP (0.035 mM) are compatible with an important role of PEPCK, as suggested by previous NMR experiments, on the CO2 fixation in vivo which leads to succinate excretion during aerobic fermentation of glucose.