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Composite electrochemical coatings (CECs) are perceived as the result of the electrochemical reduction of metal from an electrolyte in which dispersed phase particles are present. During the formation of the coating, particles are included in its volume and a composite layer is formed that has increased performance characteristics. The article discusses a different approach based on crystallization of the strengthening phase from an electrodeposited layer of a Ni–W alloy of nonequilibrium composition. It has been shown that the optimal heat treatment mode, which ensures maximum microhardness, leads to the formation of a nanostructured matrix from a solid solution of tungsten in nickel and the crystallization of NiW and Ni4W reinforcing particles. The structure of such a coating corresponds to the structure of classical CECs.

Abstract: This article discusses the influence of the cell size of the initial template, solution concentration, and number of impregnation stages on the macrostructural and strength characteristics of glassy carbon foams produced by template synthesis. The Novolak resin SFP-012A2 was used as a carbon precursor; its coke residue is higher than 57 wt %. Increasing the number of impregnation stages makes it possible to improve the strength characteristics while maintaining open porosity at the level of 90%. The best set of properties is demonstrated by glassy carbon foam based on polyurethane template with a porosity of 60 pores/inch and four impregnation stages using a solution with a concentration of 30 wt % due to uniform wall thickening in the material. The ultimate compression strength is 1.12 MPa, which is two times higher than that of foreign analogs; the open porosity is 91%. A decrease in the cell size of initial templates can lead to embrittlement of the material due to the formation of clusters of overlapped cells. Increasing the mechanical strength of glassy carbon foams while maintaining an open-cell structure expands the range of applications for this class of materials.

Abstract: The microhardness, coefficient of friction, elastic modulus, elastic recovery coefficients, and plastic deformation resistance are determined for functional aluminum matrix–carbon nanofibers coatings. Wear rate tests were carried out to evaluate the wear resistance of functional coatings, as well as to predict their service life. The coatings with the best mechanical and wear resistance characteristics were distinguished as well.

The synthesis of a composite coating with an (R–OOO)FT polyimide matrix is described and results of studying the tribological behavior of this coating are presented. Spherical 40-nm tungsten disulfide nanoparticles produced using gas-phase synthesis are used as a filler.

One- and two-step syntheses of composite coatings with an A–OOO polyimide matrix filled with 40-nm tungsten disulfide nanoparticles produced using gas-phase synthesis, which are intended for operation under dry friction conditions, are described. Results of studying the tribological behavior of these coatings are presented.

A synthesis is described and tribological characteristics are presented for composite coatings 40 μm thick with a PM–DADPE polyimide matrix and a filler of tungsten disulfide nanoparticles with size of 4 nm and tungsten diselenide nanoparticles 60 × 5 nm in size obtained via gas-phase synthesis.

To investigate residues involved in the formation of the noncatalytic nucleotide binding sites of the vacuolar proton-translocating adenosine triphosphatase (V-ATPase), cysteine scanning mutagenesis of the VMA2 gene that encodes the B subunit in yeast was performed. Replacement of the single endogenous cysteine residue at position 188 gave rise to a Cys-less form of the B subunit (Vma2p) which had near wild-type levels of activity and which was used in the construction of 16 single cysteine-containing mutants. The ability of adenine nucleotides to prevent reaction of the introduced cysteine residues with the sulfhydryl reagent 3-(N-maleimidopropionyl)biocytin (biotin-maleimide) was evaluated by Western blot. Biotin-maleimide labeling of the purified V-ATPase from the wild-type and the mutants S152C, L178C, N181C, A184C, and T279C was reduced after reaction with the nucleotide analog 3'-O-(4-benzoyl)benzoyladenosine 5'-triphosphate (BzATP). These results suggest the proximity of these residues to the nucleotide binding site on the B subunit. In addition, we have examined the level of endogenous nucleotide bound to the wild-type V-ATPase and to a mutant (the A subunit mutant R483Q) which is postulated to be altered at the noncatalytic site and which displays a marked nonlinearity in ATP hydrolysis (MacLeod, K. J., Vasilyeva, E., Baleja, J. D., and Forgac, M. (1998) J. Biol. Chem. 273, 150-156). The R483Q mutant contained 2.6 mol of ATP/mol of V-ATPase compared with the wild-type enzyme, which contained 0.8 mol of ATP/mol of V-ATPase. These results suggest that binding of additional ATP to the noncatalytic sites may modulate the catalytic activity of the enzyme.

The vacuolar (H(+))-ATPases (or V-ATPases) are structurally related to the F(1)F(0) ATP synthases of mitochondria, chloroplasts and bacteria, being composed of a peripheral (V(1)) and an integral (V(0)) domain. To further investigate the arrangement of subunits in the V-ATPase complex, covalent cross-linking has been carried out on the V-ATPase from clathrin-coated vesicles using three different cross-linking reagents. Cross-linked products were identified by molecular weight and by Western blot analysis using polyclonal antibodies raised against individual V-ATPase subunits. In the intact V(1)V(0) complex, evidence for cross-linking of subunits C and E, D and F, as well as E and G by disuccinimidyl glutarate was obtained, while in the free V(1) domain, cross-linking of subunits H and E was also observed. Subunits C and E as well as D and E could be cross-linked by 1-ethyl-3-(dimethylaminopropyl)carbodiimide, while subunits a and E could be cross-linked by 4-(N-maleimido)benzophenone. It was further demonstrated that it is possible to treat the V-ATPase with potassium iodide and MgATP in such a way that while subunits A, B, and H are nearly quantitatively removed, significant amounts of subunits C, D, E, and F remain attached to the membrane, suggesting that one or more of these latter subunits are in contact with the V(0) domain. In addition, treatment of the V-ATPase with cystine, which modifies Cys-254 of the catalytic A subunit, results in dissociation of subunit H, suggesting communication between the catalytic nucleotide binding site and subunit H. Finally, the stoichiometry of subunits F, G, and H were determined by quantitative amino acid analysis. Based on these and previous observations, a new structural model of the V-ATPase from clathrin-coated vesicles is proposed.

Molecular modeling studies have previously suggested the possible presence of four aromatic residues (Phe(452), Tyr(532), Tyr(535), and Phe(538)) near the adenine binding pocket of the catalytic site on the yeast V-ATPase A subunit (MacLeod, K. J., Vasilyeva, E., Baleja, J. D., and Forgac, M. (1998) J. Biol. Chem. 273, 150-156). To test the proximity of these aromatic residues to the adenine ring, the yeast V-ATPase containing wild-type and mutant forms of the A subunit was reacted with 2-azido-[(32)P]ADP, a photoaffinity analog that stably modifies tyrosine but not phenylalanine residues. Mutant forms of the A subunit were constructed in which the two endogenous tyrosine residues were replaced with phenylalanine and in which a single tyrosine was introduced at each of the four positions. Strong ATP-protectable labeling of the A subunit was observed for the wild-type and the mutant containing tyrosine at 532, significant ATP-protectable labeling was observed for the mutants containing tyrosine at positions 452 and 538, and only very weak labeling was observed for the mutants containing tyrosine at 535 or in which all four residues were phenylalanine. These results suggest that Tyr(532) and possibly Phe(452) and Tyr(538) are in close proximity to the adenine ring of ATP bound to the A subunit. In addition, the effects of mutations at Phe(452), Tyr(532), Tyr(535), and Glu(286) on dissociation of the peripheral V(1) and integral V(0) domains both in vivo and in vitro were examined. The results suggest that in vivo dissociation requires catalytic activity while in vitro dissociation requires nucleotide binding to the catalytic site.

The structure of the vacuolar ATPase from bovine brain clathrin-coated vesicles has been determined by electron microscopy of negatively stained, detergent-solubilized enzyme molecules. Preparations of both lipid-containing and delipidated enzyme have been analyzed. The complex is organized in two major domains, a V(1) and V(0), with overall dimensions of 28 x 14 x 14 nm. The V(1) is a more or less spherical molecule with a central cavity. The V(0) has the shape of a flattened sphere or doughnut with a radius of about 100 A. The V(1) and V(0) are joined by a 60-A long and 40-A wide central stalk, consisting of several individual protein densities. Two kinds of smaller densities are visible at the top periphery of the V(1), and one of these seems to extend all the way down to the stalk domain in some averages. Images of both the lipid-containing and the delipidated complex show a 30-50-kDa protein density on the lumenal side of the complex, opposite the central stalk, centered in the ring of c subunits. A large trans-membrane mass, probably the C-terminal domain of the 100-kDa subunit a, is seen at the periphery of the c subunit ring in some projections. This large mass has both a lumenal and a cytosolic domain, and it is the cytosolic domain that interacts with the central stalk. Two to three additional protein densities can be seen in the V(1)-V(0) interface, all connected to the central stalk. Overall, the structure of the V-ATPase is similar to the structure of the related F(1)F(0)-ATP synthase, confirming their common origin.

The published experimental data and existing concepts of cellular regulation of respiration are analyzed. Conventional, simplified considerations of regulatory mechanism by cytoplasmic ADP according to Michaelis-Menten kinetics or by derived parameters such as phosphate potential etc. do not explain relationships between oxygen consumption, workload and metabolic state of the cell. On the other hand, there are abundant data in literature showing microheterogeneity of cytoplasmic space in muscle cells, in particular with respect to ATP (and ADP) due to the structural organization of cell interior, existence of multienzyme complexes and structured water phase. Also very recent experimental data show that the intracellular diffusion of ADP is retarded in cardiomyocytes because of very low permeability of the mitochondrial outer membrane for adenine nucleotidesin vivo. Most probably, permeability of the outer mitochondrial membrane porin channels is controlled in the cellsin vivo by some intracellular factors which may be connected to cytoskeleton and lost during mitochondrial isolation. All these numerous data show convincingly that cellular metabolism cannot be understood if cell interior is considered as homogenous solution, and it is necessary to use the theories of organized metabolic systems and substrate-product channelling in multienzyme systems to understand metabolic regulation of respiration. One of these systems is the creatine kinase system, which channels high energy phosphates from mitochondria to sites of energy utilization. It is proposed that in muscle cells feed-back signal between contraction and mitochondrial respiration may be conducted by metabolic wave (propagation of oscillations of local concentration of ADP and creatine) through cytoplasmic equilibrium creatine and adenylate kinases and is amplified by coupled creatine kinase reaction in mitochondria. Mitochondrial creatine kinase has experimentally been shown to be a powerful amplifier of regulatory action of weak ADP fluxes due to its coupling to adenine nucleotide translocase. This phenomenon is also carefully analyzed.

The short preincubation of submitochondrial particles with low concentrations of ADP in the presence of Mg2+ results in a complete loss of their ATPase and inosine triphosphatase activities. Other nucleoside diphosphates (IDP and GDP) do not affect the ATPase activity. The ADP-inhibited ATPase can be activated in a time-dependent manner by treatment of submitochondrial particles with the enzyme converting ADP into ATP (phosphoenolpyruvate plus pyruvate kinase). The activaton is a first-order reaction with rate constant 0.2 min-1 at 25 degrees C. The rate constant of activation is increased in the presence of ATP up to 2 min-1, and this increase shows saturation kinetics with Km value equal to that for ATPase reaction itself (10(-4) M at 25 degrees C at pH 8.0). The experimental results obtained are consistent with the model where two alternative pathways of ADP dissociation from the inhibitory site of ATPase exist; one is spontaneous dissociation and the second is ATP-dependent dissociation through the formation of the ternary complex between ADP, the enzyme and ATP. ADP-induced inactivation and ATP-dependent activation of ATPase activity of submitochondrial particles is accompanied by the same directed change of their ability to catalyse the ATP-dependent reverse electron transport from succinate to NAD+. The possible implication of the model suggested is discussed in terms of functional role of the inhibitory high-affinity binding site for ADP in the mitochondrial ATPase.

To investigate the function of residues at the catalytic nucleotide binding site of the V-ATPase, we have carried out site-directed mutagenesis of the VMA1 gene encoding the A subunit of the V-ATPase in yeast. Of the three cysteine residues that are conserved in all A subunits sequenced thus far, two (Cys284 and Cys539) appear essential for correct folding or stability of the A subunit. Mutation of the third cysteine (Cys261), located in the glycine-rich loop, to valine, generated an enzyme that was fully active but resistant to inhibition by N-ethylmalemide, 7-chloro-4-nitrobenz-2-oxa-1,3-diazole, and oxidation. To test the role of disulfide bond formation in regulation of vacuolar acidification in vivo, we have also determined the effect of the C261V mutant on targeting and processing of the soluble vacuolar protein carboxypeptidase Y. No difference in carboxypeptidase Y targeting or processing is observed between the wild type and C261V mutant, suggesting that disulfide bond formation in the V-ATPase A subunit is not essential for controlling vacuolar acidification in the Golgi. In addition, fluid phase endocytosis of Lucifer Yellow, quinacrine staining of acidic intracellular compartments and cell growth are indistinguishable in the C261V and wild type cells. Mutation of G250D in the glycine-rich loop also resulted in destabilization of the A subunit, whereas mutation of the lysine residue in this region (K263Q) gave a V-ATPase complex which showed normal levels of A subunit on the vacuolar membrane but was unstable to detergent solubilization and isolation and was totally lacking in V-ATPase activity. By contrast, mutation of the acidic residue, which has been postulated to play a direct catalytic role in the homologous F-ATPases (E286Q), had no effect on stability or assembly of the V-ATPase complex, but also led to complete loss of V-ATPase activity. The E286Q mutant showed labeling by 2-azido-[32P]ATP that was approximately 60% of that observed for wild type, suggesting that mutation of this glutamic acid residue affected primarily ATP hydrolysis rather than nucleotide binding.

Kinetics of regulation of respiration by ADP in skinned cardiac fibers and permeabilized isolated hepatocytes was compared before and after mitochondrial swelling due to hypoosmotic treatment in 30-50 mOsM solutions. In both systems the apparent Km for ADP was high before mitochondrial swelling and equal to 297 ± 35 μM and 275 ± 35 μM, correspondingly. Hypoosmotic treatment resulted in the rupture of outer mitochondrial membrane and in the loss of exogenous cytochrome c, and both in skinned cardiac fibers and permeabilized hepatocytes the value of apparent Km for ADP was decreased in correlation with the extent of the rupture of the outer mitochondrial membrane. It is concluded that both in heart and liver cells in vivo, the ADP diffusion in the cells is retarded due to very low permeability of the outer mitochondrial membrane for ADP.

It was previously observed that the B subunit of the tonoplast V-ATPase is modified by the photoactivated nucleotide analog 3'-O-(4-benzoyl)benzoyladenosine 5'-triphosphate (BzATP) (Manolson, M. F., Rea, P. A., and Poole, R. J. (1985) J. Biol. Chem. 260, 12273-12279). We have further characterized the nucleotide binding sites on the V-ATPase and the interaction between BzATP and the B subunit. We observe that the V-ATPase isolated from bovine clathrin-coated vesicles possesses approximately 1 mol of endogenous, tightly bound ATP/mol of V-ATPase complex. BzATP is not a substrate for the V-ATPase, but does act as a noncovalent inhibitor in the absence of irradiation, changing the kinetic characteristics of ATP hydrolysis. Irradiation of the V-ATPase in the presence of [3H]BzATP results primarily in modification of the 58-kDa B subunit, with complete inhibition of V-ATPase activity occurring upon modification of one B subunit per V-ATPase complex. Inhibition occurs as the result of modification of a rapidly (t1/2 < 2 min) exchangeable site, and yet this site does not correspond to a catalytic site, as indicated by the effects of cysteine-modifying reagents which react with Cys254 located at the catalytic sites on the A subunit. Thus, the noncatalytic nucleotide binding site modified by BzATP appears to be rapidly exchangeable. The site of [3H]BzATP modification of the B subunit was localized to the region Ile164 to Gln171, which from the x-ray crystal structure of the homologous F-ATPase alpha subunit, is within 10 A of the ribose ring of ATP bound to the noncatalytic nucleotide binding site. Thus, despite the absence of a glycine-rich loop region in the B subunit, these data are consistent with a similar overall folding pattern for the V-ATPase B subunit and the F-ATPase alpha subunit.

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To further define the structure of the nucleotide binding sites on the vacuolar proton-translocating ATPase (V-ATPase), the role of aromatic residues at the catalytic sites was probed using site-directed mutagenesis of the VMA1 gene that encodes the A subunit in yeast. Substitutions were made at three positions (Phe452, Tyr532, and Phe538) that correspond to residues observed in the crystal structure of the homologous beta subunit of the bovine mitochondrial F-ATPase to be in proximity to the adenine ring of bound ATP. Although conservative substitutions at these positions had relatively little effect on V-ATPase activity, replacement with nonaromatic residues (such as alanine or serine) caused either a complete loss of activity (F452A) or a decrease in the affinity for ATP (Y532S and F538A). The F452A mutation also appeared to reduce stability of the V-ATPase complex. These results suggest that aromatic or hydrophobic residues at these positions are essential to maintain activity and/or high affinity binding to the catalytic sites of the V-ATPase. Site-directed mutations were also made at residues (Phe479 and Arg483) that are postulated to be contributed by the A subunit to the noncatalytic nucleotide binding sites. Generally, substitutions at these positions led to decreases in activity ranging from 30 to 70% relative to wild type as well as modest decreases in Km for ATP. Interestingly, the R483E and R483Q mutants showed a time-dependent increase in ATPase activity following addition of ATP, suggesting that events at the noncatalytic sites may modulate the catalytic activity of the enzyme.

Previous studies have indicated that the 73-kDa A subunit of the coated vesicle V-ATPase possesses a nucleotide-binding site essential for activity (Arai, H., Berne, M., Terres, G., Terres, H., Puopolo, K., and Forgac, M. (1987) Biochemistry 26, 6632-6638) and have identified a cysteine residue (Cys254) whose modification leads to complete loss of activity (Feng, Y., and Forgac, M. (1992) J. Biol. Chem. 267, 5817-5822). To further characterize the structure of the nucleotide-binding sites of the V-ATPase, labeling studies using the photoactivated analog 2-azido-[32P]ATP have been carried out. We have observed that 2-azido-[32P]ATP is hydrolyzed by the V-ATPase at a rate (at 1 mM) approximately 4-fold lower than observed for ATP, indicating that 2-azido-[32P]ATP is a good substrate for the V-ATPase. Irradiation of the V-ATPase in the presence of 0.5 mM 2-azido-[32P]ATP leads to inactivation of V-ATPase activity with a t1/2 of 3-5 min. The 73-kDa A subunit, the 58-kDa B subunit, and the 50-kDa subunit of the AP-2 adaptin complex (Myers, M., and Forgac, M. (1993) J. Biol. Chem. 268, 9184-9186) are all labeled in an ATP-protectable manner on irradiation of the purified V-ATPase with 2-azido-[32P]ATP. The time course for inactivation most closely correlates with labeling of the A subunit. Measurement of the stoichiometry of 2-azido-[32P]ATP incorporation into the A subunit as a function of inactivation indicates that complete loss of activity is obtained on incorporation of 1.2 mol of 2-azido-[32P]ATP/mol V-ATPase complex. 2-Azido-[32P]ATP labeling indicates that the V-ATPase possesses both rapidly (t1/2 < 2 min) and slowly (t1/2 > 2 min) exchangeable nucleotide-binding sites. The A subunit is labeled upon modification of both rapidly and slowly exchangeable sites whereas the B subunit is labeled upon modification of only rapidly exchangeable sites. Inhibition of V-ATPase activity correlates with labeling of the rapidly exchangeable sites. Amino acid sequence analysis of peptides derived from the 2-azido-[32P]ATP-labeled A subunit indicates labeling of two peptides: a 12-kDa fragment which begins at residue 511 and contains Cys532 and a 3-kDa fragment which begins at residue 233 and contains the glycine-rich loop and Cys254. Only the 12-kDa fragment is labeled upon modification of the rapidly exchangeable sites.(ABSTRACT TRUNCATED AT 400 WORDS)

1. The initial rapid phase of ATP hydrolysis by bovine heart submitochondrial particles or by soluble F1-ATPase is insensitive to anion activation (sulphite) or inhibition (azide). 2. The second slow phase of ATP hydrolysis is hyperbolically inhibited by azide (Ki approximately 10(-5) M); the inosine triphosphatase activity of submitochondrial particles or F1-ATPase is insensitive to azide or sulphite. 3. The rate of interconversion between rapid azide-insensitive and slow azide-sensitive phases of ATP hydrolysis does not depend on azide concentration, but strongly depends on ATP concentration. 4. Sulphite prevents the interconversion of the rapid initial phase of the reaction into the slower second phase, and also prevents and slowly reverses the inhibition by azide. 5. The presence of sulphite in the mixture when ADP reacts with ATPase of submitochondrial particles changes the pattern of the following activation process. 6. Azide blocks the activation of ATP-inhibited ATPase of submitochondrial particles by phosphoenolpyruvate and pyruvate kinase. 7. The results obtained suggest that the inhibiting effect of azide on mitochondrial ATPase is due to stabilization of inactive E*.ADP complex formed during ATP hydrolysis; the activation of ATPase by sulphite is also realized through the equilibrium between intermediate active E.ADP complex and inactive E*.ADP complex.

1. A substantial increase of the initial rate of ATP hydrolysis was observed after preincubation of bovine heart submitochondrial particles with phosphoenolpyruvate and pyruvate kinase. 2. The activation was accompanied by an increase of Vmax, without change of Km for ATP. 3. The activated particles catalysed the biphasic hydrolysis of ATP in the presence of an ATP-regenerating system; the initial rapid phase was followed by a second, slower, phase in a time-dependent fashion. 4. The higher the ATP concentration used as a substrate, the higher is the rate of transition between these two phases. 5. The particles catalysed the hydrolysis of ITP with a lag phase; after preincubation with phosphoenolpyruvate and pyruvate kinase, ITP was hydrolysed at a constant rate. 6. Qualitatively the same phenomena were observed when soluble mitochondrial ATPase (F1-ATPase) prepared by the conventional method in the presence of ATP was used as nucleotide triphosphatase. 7. A kinetic scheme is proposed, in which the intermediate active enzyme-product complex (E.ADP) formed during ATP hydrolysis is in slow equilibrium with the inactive E*.ADP complex forming as a result of dislocation of ADP from the active site of ATPase to the other site, which is not in rapid equilibrium with the surrounding medium.

The kinetics of adenosine triphosphate (ATP)-dependent proton transport into clathrin-coated vesicles from bovine brain have been studied. We observe that the vacuolar proton-translocating ATPase (V-ATPase) from clathrin-coated vesicles is subject to two different types of inhibition by ADP. The first is competitive inhibition with respect to ATP, with a Ki for ADP of 11 microM. The second type of inhibition occurs after preincubation of the V-ATPase in the presence of ADP and Mg2+, which results in inhibition of the initial rate of proton transport followed by reactivation over the course of several minutes. The second effect is observed at ADP concentrations as low as 0.1-0.2 microM, indicating that a high affinity inhibitory complex is formed between ADP and the V-ATPase and is only slowly dissociated after the addition of ATP. We have further investigated the effect of sodium azide, an inhibitor of the F-ATPases that has been shown to stabilize an inactive complex between ADP and the F1-F0-ATP synthase (F-ATPase). We observed that azide inhibited ATP-dependent proton transport by the purified, reconstituted V-ATPase with a K0.5 of 0.2-0.4 mM but had no effect on ATP hydrolysis. Azide was shown not to increase the passive proton permeability of reconstituted vesicles and did not stimulate ATP hydrolysis by the reconstituted enzyme, in contrast with CCCP, which both abolished the proton gradient and stimulated hydrolysis. Thus, azide does not appear to act as a simple uncoupler of proton transport and ATP hydrolysis. Rather, azide may have some more direct effect on V-ATPase activity. Possible mechanisms by which azide could exert this effect on the V-ATPase and the contrasting effects of azide on the F- and V-ATPases are discussed.

Summary 1.A method is proposed for the separation of a mixture of an amino acid and ammonium chloride with the aid of cation-exchange resins.2.It is shown that some amino carboxylic acids can be isolated from their hydrochlorides with the aid of cation-exchange resins.3.It is shown that the Soviet cationites SBS, SBSR, and SDV can be successfully applied or the separation of amino carboxylic acids from ammonium chloride.

Summary 1.It has been shown, on the basis of ß,ß-diphenylpropionylmesitylene as example, that the sodium derivatives of keto compounds exist in two cis-trans stereoisomeric forms, and that they are therefore enolates.2.On benzoylating the stereoisomeric Na enolates at room temperature, the corresponding stereoisomeric enol-benzoates are formed. On methoxymethylating, they give the corresponding stereoisomeric O-methoxymethyl derivatives together with one form only of C-methoxymethyl derivative.3.On replacing Na by (CH3)3C6H5N+, the stereoisomers, instead of reacting differently, react in identical fashion (with benzoyl chloride and chloromethyl methyl ether). Also, a C-methoxymethyl derivative is not formed.4.It has been shown that the sodium enolates are considerably more labile than the lithium and, particulary, the magnesium enolates, which were studied previously. Thus, on heating, the sodium enolates are mutually converted, giving a mixture in which the more stable enolate predominates.5.As in the case of the Li and NgBr enolates, the conclusion is reached that the dual reactivity (alkylation or acylation on O and on C) of Na enolates is, in the first place, not due to the reversible isomerization (tautomerization) of these enolates into a keto form containing a C-metal bond and, in the second place, not due to the presence of an ionic structure in these enolates and to dual reactivity in the mesomeric ion.6.The hypothesis previously put forward concerning the transfer of the reactive center of the molecule along a system of conjugated (Na-O and C-C) bonds as the cause of the dual reactivity (at O and at C) of metal enolates is confirmed.

Ameliorants (materials which have very high ionic capacity and hold moisture) are applied for long-term improvement of soil's features in production of crops. A device is elaborated for liquid ameliorants' importation into the subsoil space which allows increasing uniformity of an importation and quality of their dispersion in the space under a flat hoe at sweep soil cultivation. This tool contains supply pipe-line with the distributive openings which are evenly located on its length, a material stream divider, the channel of supply of material and the air duct with openings. We have conducted preliminary laboratory researches in which two types of springs were applied: with the equidistant coils and with the decreasing step-by-step distance of coils to an extreme last opening. In the second case the identical rate of flow from openings was observed because the pressure was supported on all length of the pipeline. Thus, as a result of the theoretical analysis and laboratory experiments we established dependence of design data's change of the coil on the created pressure on width of the developed device for the local importation of liquid ameliorants into the soil at sweep soil cultivation.

Recent study considers the tribological characteristics of the sintered bushings used in the connecting nodes brake lever system of railway cars. Particular attention is paid sleeves low content of alloying elements. Bushings had been prepared by powder metallurgy route by using low alloyed powders of Fe-Cu-C system. Porosity after sintering was about 20%. Generally, before using material was impregnated by industrial mineral oil in order to improve friction condition. In the recent study we use new lubricating compositions for impregnating in sintered bodies. Such compositions consist of basic mineral oil with addition of 4 wt.% of layered tungsten dichalcogenides (WS2 and WSe2) nanoparticles, which were ultrasonically dispersed. Tungsten disulphide nanoparticles have spherical shape with the diameter of 30-50 nm, and diselenide nanoparticles have a flat shape with the mean dimensions of 5x70 nm. Tribological testing of the product was provided. Sintered bushings impregnated with commercial oil and suspension of nanoparticles were tested in the spinning friction conditions in the couple with bearing steel at the load of 210 N and spinning rate of 200 rpm. The friction test in couple with steel exhibited the value of friction moment to be about 2 times less as compared with commercial oil. The additions of tungsten disulphide nanoparticles also significantly decrease oscillations the friction torque.