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A new enzymatic photometric assay for determination of methanol and ethanol in solutions containing both alcohols is described. The assay allows detecting methanol in the concentration range of tens ppm of in the presence of tens per cent of ethanol. The lower determination threshold for methanol is at least 0.002% in the presence of 45% ethanol, with a coefficient of variation of 0.02-0.05. General-purpose spectrophotometers and photoelectric colorimeters can be used in the measurements.

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A novel enzymatic photometric assay for ethanol determination using alcohol oxidase and peroxidase is described. The sensitivity of the method allows detecting ethanol in biological fluids (saliva and blood serum). Secondary alcohols and other organic compounds do not interfere with the assay. General-purpose spectrophotometers and photoelectric colorimeters can be used in the measurements. Methanol and propanol can also be determined by this technique.

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A modified urease hypochlorite method for measuring urea in biological fluids is described. Its novel feature is the use of 4-hydroxycoumarin as ammonia acceptor. This compound has never been used for this purpose, and it has a number of advantages over traditional phenol and its derivatives: the measurement is performed in just two steps, the compound is nontoxic and used in low concentrations, and the accuracy of measurements is higher due to decrease of the systemic error. Results of urea tests with the new kit are presented. The kit contains ready-to-use components in tablets and stabilized concentrated solutions of sodium hypochlorite and alkali. The characteristics of the kit are as follows: linearity of determination up to 25 mmoles per liter, deviation from linearity no more than 7%, and sensitivity up to 0.7 mmoles/liter.

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A chemiluminescent method has been offered to assay the blood serum total cholesterol. The method is based on coupled enzymatic reactions in two steps: (1) esterified cholesterol hydrolysis by cholesterol esterase in the presence of sodium cholate and (2) cholesterol oxidation by cholesterol oxidase and chemiluminescent assay of the released hydrogen peroxide in peroxidase reaction with luminol and p-iodophenol. Separation of these steps results in a better accuracy of the test as against the one-step procedure. High sensitivity of the method (the detection limit being 1 mM of cholesterol in a luminometer cuvette) permits high dilutions of the serum, this essentially eliminating the admixture effects on the enzymatic reactions. The findings of the suggested method are in good correlation with those of the spectrophotometric assay of cholesterol using the KONE kit.

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It was shown that six redox indicators, beside oxygen, can be used as substrates for glucose oxidase from Penicillium vitale. The pH dependence of the rate of glucose oxidase-catalyzed reactions in the presence of oxygen and artificial electron acceptors was studied. In contrast to the reaction involving oxygen, in which the maxima of the pH activity profile were observed at pH 5.6, glucose oxidase reveals maximal pH activity profile at pH 7.5 -- 7.6 in the presence of phenasine methosulfate, basic dark-blue 2K, viologens and ion-radical salt of N,N,N',N'-tetramethyl-rho-phenylene diamine. It was assumed that there exist two forms of the reduced enzyme differing in their rates of oxidation by oxygen and in ability to reduce artificial electron acceptors via one-electron transfer.

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The sedimentation behaviour of the subform of rabbit muscle phosphofructokinase specifically eluted from DEAE cellulose by citrate was studied in different media by velocity experiments. The measured sedimentation coefficients of different components in the system can be classified into 12 groups, which is indicative of a complex multistep association process of the enzyme (with more than 3 oligomers). The concentration dependence of weight average sedimentation coefficient of phosphofructokinase was a studied. The choice of the probable association model of phosphofructokinase oligomers at low protein concentration was accomplished by means of computer simulation of the association process. Of 26 closed association models tested 14 models with 2 or 3 association constants are indistinguishable in view of Student's t-criterion of significance. All uniparametric association models studied significantly inferior approximate the experimental data. It is supposed that the dimer is not the structural unit of polymerization. Having this in mind and taking into account the demand for the multistep process, one may consider as most probable only 8 models of phosphofructokinase association, namely monomer-dimer-trimer-tetramer-monomer-dimer-tetramer-octamer (with 3 association constants) and linear polymerization up to the octamer with 2 association constants, where the "monomer" of association may be defined as trimer, tetramer or hexamer of subunits.

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The cells of Achromobacter parvulus, strain 1T, when grown in a methanol-containing medium, have two formate dehydrogenases, i.e. NAD-linked formate dehydrogenase and the formate dehydrogenase reducing the ferricyanide and tetrazolia. Only the latter enzyme was found in the cells grown in a medium with glycerol as a carbon source. These enzymes differ with respect to Km for formate and antigenic specificity. Km for formate oxidation by the cells of A. parvulus is lower than for formate of the NAD-dependent formate dehydrogenase and is equal to Km for the enzyme reducing artificial electron acceptors. The results obtained are discussed in terms of the existence of two cytochrome oxidase systems in the methylotrophic bacteria, differing in their sensitivities to the inhibition by formate.

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Whole cells and cell-free preparations of the methylotrophic bacteria, Pseudomonas sp. AM 1 and Achromobacter parvulus, can oxidize formate at tis concentration in the reaction medium up to 1 M. The respiration of whole cells is registered at a concentration of formate greater than 10(-2) M, while that of cell-free extracts at a formate concentration greater than 5 X 10(-5) M. This seems to be due to the presence of a permeability barrier in cells for formate. The oxidation of reduced TMPD and exogenous cytochrome c by the membrane preparations of the two bacteria is inhibited by formate and cyanide; Ki50% = 2.5 X 10(-2) and 10(-6) M, respectively. The oxidation of NADH by the membrane preparations of the bacteria is not inhibited by 1 M formate and 5 X 10(-4) M cyanide but is inhibited by formaldehyde with Ki50% = 3 X 10(-2) M. Formaldehyde has no effect on the oxidation of reduced TMPD and cytochrome c at concentrations greater than 2 X 10(-1) M. These data indicate that respiration of the studied methylotrophic bacteria in the presence of high formate concentrations should be attributed in the presence of a branched electron transport chain in them; one branch of the chain is resistant to formate and cyanide, but is sensitive to formaldehyde.

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The process of electrochemical oxidation of formate on a coal electrode with the help of a two-enzyme system composed of NAD-dependent formate dehydrogenase and NADH-dehydrogenase, catalysing oxidation of NADH with reduction of methylviologen was studied. In this system the oxidation of formate proceeds in the diffusion regime. Under experimental conditions the value of current density at a potential higher than +0,2 V and at the rotating rate of 600 rpm is 12 mA/cm2. The results obtained show that NAD-depend dehydrogenases can be used for electrochemical oxidation of organic compounds which are their substrates.

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NAD-Dependent formate dehydrogenase (FDH) has been isolated from methylotrophyc strain Bacterium sp 1 by (NH4)2SO4 fractionation of cell extract, ion-exchange chromatography and preparative isotachophoresis. Preparation of FDH is homogeneous in analytical polyacrylamide gel electrophoresis and under ultracentrifugation. Sedimentation coefficient of FDH is 4.9S. Mikhaelis constants are 1.1-10(-4) M for NAD and 1.5-10(-2) M for formate. In the absence of sulfhydril compounds FDH is unstable, but it is stable in the presence of mercaptoethanol or ditiotreitol.

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It has been shown that ganglioside micellae were able to reversible interaction with serotonin; the interaction is determined by their composition. Ganglioside and ganglioside-serotonin micellae were equal in sizes if pH, the ionic strength and the type of the buffer, the temperature and serotonin concentration were given. When the ganglioside micellae were saturated with serotonin the micallae became able to jumping reconstruction forming the structure able to bind more serotonin than the first one. As the serotonin concentration was increased CCM of mixed serotonin-ganglioside micellae was reached. It has been suggested that the reconstruction of the ganglioside micelle due to its interaction with serotonin can be considered as a model of a cooperative transfer of the postsynaptical membrane when a nervous impulse passes through a synapse.

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