Comparative study of horseradish mutant forms by radioenzymology

Radioenzymology was used to study the recombinant and mutant forms of horseradish peroxidase, namely, F221W, Q176E, Q176A, S35K, E64P, E64S, S35A, and S35KQ176E. Both removal of the Trp residue and introduction of an additional one result in a simpler dose response; the insertion of polar residues stabilizes the enzyme molecule through realization of a more closed conformation. The greatest oscillation changes were found for the replacement by Ala. It was assumed that the binding site of guaiacol as a substrate is located near the residue 64, which is structurally related to the residue 176 and the heme. A scheme of formation of the intermediate through rotation of the Trp aromatic ring was proposed.     

Synthesis of 3-amino-4-hydroxylaminothiazolidine-2-thiones and 2,3-dimethyl-4a,5-dihydro-7-thioxothiazolo[3,4-b]-1,2,4-triazines

The reaction of dimeric nitroso chlorides of olefins with potassium dithiocarbazate was used to synthesize 3-amino-4-hydroxylaminothiazolidine-2-thiones, which undergo rearrangement to 2-mercapto-1,3,4-thiadiazines on heating and react with butane-2,3-dione to give 2,3-dimethyl-4a,5-dihydro-7-thioxothiazolo[3,4-b]-1,2,4-triazine 4-oxides. The latter are reduced by sodium borohydride to the corresponding 3,4,4a,5-tetrahydro-7-thioxo derivatives.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, pp. 554–556, April, 1987.     

Sustainable treatment and reuse of diluted pig manure streams in Russia: from laboratory trials to full-scale implementation

This article summarizes the results obtained during the laboratory and pilot development of integrated biologic and physicochemical treatment and reuse of diluted pig manure streams. The application of a straw filter was an effective means to separate the solid and liquid fractions of raw wastewater and resulted in the removal of a significant part of the dry matter, total nitrogen, and phosphorus (65, 27, and 32%, respectively). From the filtrate generated, 60–80% of the total chemical oxygen demand (COD) was removed in an upflow anaerobic sludge bed reactor operating at 15–30°C. Ammonia was efficiently eliminated (>99%) from the anaerobic effluents using Ural laumantite as an ion exchanger. However, the nitrogen-content of the zeolite was too low to consider this method of ammonia removal economically feasible. The phosphate precipitation block, consisting of stripper of CO₂ and fluidized-bed crystallizator, was able to decrease the concentration of soluble phosphate in the anaerobic effluents up to 7–15 mg of phosphate/L. The application of aerobic/anoxic biofilter as a sole polishing step was acceptable from an aesthetic point of view (the effluents were transparent and almost colorless and odorless) and elimination of biochemical oxygen demand (the resting COD was hardly biodegradable). However, the effluent nutrient concentrations (especially nitrogen) were far from the current standards for direct discharge of treated wastewater. We discuss the approaches for further improvement of effluent quality. Finally, we provide an outline of a full-scale system that partially implements the laboratory- and pilot-scale results obtained.     

Formation of H-bonded ionic associates in reactions of 5-nitrosalicylaldehyde with secondary amines

5-Nitrosalicylaldehyde reacts with highly basic secondary aliphatic amines to form molecular complexes of 1 1 composition. The complexes with piperidine, diethylamine, dipentylamine, and dibenzylamine (1–4, respectively) have been obtained in the crystalline state and characterized. The X-ray diffraction structural analysis of complex1 demonstrated that it exists in a crystal as an H-bonded dimeric ionic associate [C₅H₁₂N⁺ · C₇H₄NO ₄ ^– ]₂ formed as a result of the transfer of the phenyl proton of the aldehyde to the piperidine N atom. According to the results of IR spectroscopy, the other complexes obtained have similar structures.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 940–943, May, 1995.     

Study of the telomerization of ethylene and 1-hexene by butanal through comparative kinetics

The reaction of ethylene and 1-hexene with butanal was studied using tertiary butyl peroxide initiation at 140°C and a hydrostatic pressure in the range of 250–450 kg/cm². Based on calculated values of the rate constant ratios for the addition reaction of the n-C₃H₇O radical to ethylene (k₀ ^e) and 1-hexene (k₀ ^h), we obtained k₀ ^e/k₀ ^h=3.7 as the rate constant of the decarbonylation reaction of this radical (k_d). The partial chain transfer constants were calculated for the ethylene-butanal system as C_n: C₁=1.0±0.16; C₂=1.0±0.14; C₃=0.9±0.23. The results obtained indicate the nucleophilic character of the n-C₃H₇O radical in these reactions.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 6, pp. 1356–1360, June, 1990.     

Reactions with Methylamine of Pyrilo-2-cyanines Containing Polyfluorophenyl Substituents

Reactions of symmetric and unsymmetrical pyrilo-2-cyanines containing polyfluorophenyl substituents with methylamine give rise to the corresponding pyridocyanines, 1,3-cyclohexadiene derivatives, or 1-methyl-2-pyridone. The type of the reaction product depends on the structure of the initial dye and the reaction conditions.     

Thermal stability of urea complexes of magnesium nitrate and magnesium monophosphate

Urea complexes of magnesium nitrate and magnesium monophosphate were synthesized and investigated by thermal analysis, X-ray phase analysis and IR spectroscopy. It was found that the thermal stability of the complexes increases with the number of organic ligands in the complex. The mass losses corresponding to the stages of thermal decomposition of the compounds were calculated via the thermogravimetric curves. The mode of coordination between urea and Mgⁿ was investigated by IR spectroscopy.

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Zusammenfassung Harnstoffkomplexe von Magnesiumnitrat und Magnesiummohophosphat wurden synthetisiert und mittels thermischer Analyse, Röntgenphasenanalyse und IR-Spektroskopie untersucht. Die thermische Stabilität der Komplexe nimmt mit der Zahl der organischen Liganden im Komplex zu. Die thermischen Zersetzungsschritten der Verbindungen entsprechenden Massenverluste wurden aus den thermogravimetrischen Kurven ermittelt. IR-spektroskopisch wurde die Art der Koordination zwischen Harnstoff und Mg(II) untersucht.

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, , . , . , . Mg ^II.

     

Palladium nitrosoarene complexes in reductive carbonylation of nitroarenes

The reactions of carbon monoxide with the palladium nitrosoarene complexes Pd₂(-OCOR)₂(—CH₂C₆H₄NO)₂ (1, R = Me, CF₃, Bu^t, or Ph) and Pd₂(-OCOR)₂(PhNC₆H₄NO)₂ (2, R = Me, CF₃, Bu^t, or Ph) were studied. Complexes 1 contain the o-nitrosotoluene molecule metallated at the methyl group. In complexes 2, the phenyl-o-nitrosophenylamide ligand coordinated via two nitrogen atoms can be considered as a nitrosobenzene derivative bearing the NPh group in the ortho position of the Ph ring. It all cases, carbonylation of the complexes afforded the corresponding aryl isocyanates Ar—N=C=O or the products of their further transformations. The mechanism of reductive carbonylation of nitroarenes catalyzed by palladium compounds and the role of palladium nitrosoarene complexes as possible intermediates in this process are discussed.