Directed mutagenesis studies of the metal binding site at the subunit interface of Escherichia coli inorganic pyrophosphatase

Recent crystallographic studies on Escherichia coli inorganic pyrophosphatase (E-PPase) have identified three Mg2+ ions/enzyme hexamer in water-filled cavities formed by Asn24, Ala25, and Asp26 at the trimer-trimer interface (Kankare, J., Salminen, T., Lahti, R., Cooperman, B., Baykov, A. A., and Goldman, A. (1996) Biochemistry 35, 4670-4677). Here we show that D26S and D26N substitutions decrease the stoichiometry of tight Mg2+ binding to E-PPase by approximately 0.5 mol/mol monomer and increase hexamer stability in acidic medium. Mg2+ markedly decelerates the dissociation of enzyme hexamer into trimers at pH 5.0 and accelerates hexamer formation from trimers at pH 7.2 with wild type E-PPase and the N24D variant, in contrast to the D26S and D26N variants, when little or no effect is seen. The catalytic parameters describing the dependences of enzyme activity on substrate and Mg2+ concentrations are of the same magnitude for wild type E-PPase and the three variants. The affinity of the intertrimer site for Mg2+ at pH 7.2 is intermediate between those of two Mg2+ binding sites found in the E-PPase active site. It is concluded that the metal ion binding site found at the trimer-trimer interface of E-PPase is a high affinity site whose occupancy by Mg2+ greatly stabilizes the enzyme hexamer but has little effect on catalysis.     

Quantum computers: Achievements,implementation difficulties,and prospects

A review of the principles of operation of quantum computers and their elements is presented. The radical advantage of quantum algorithms for processing information over the classical ones is discussed, quantum entanglement is considered as the basic resource of quantum computations, and the most promising and interesting proposals on realization of quantum computers on the basis of trapped ions, nuclear spins, quantum dots, superconducting structures, and others are described. This review reflects the materials of the report presented at the scientific session of the Department of Nanotechnologies and Information Technologies of the Russian Academy of Sciences on February 25, 2010.     

Concentrational commensurate-incommensurate magnetic phase transition in Y1 − x Tb x Mn6Sn6

The magnetic state of Y_{1 ? x} Tb _x Mn₆Sn₆ (with x ≤ 0.25) alloy is studied at different temperatures and magnetic fields by neutron diffraction. The alloy with x _c = 0.22 exhibits an incommensurate-to-commensurate structure phase transition. The transition is accompanied by a decrease in the unit-cell volume. The weak dependence of the intensity of satellites on the x concentration and the monotonic displacement of their angular positions with increasing x allow us to conclude that the antiferromagnet → ferrimagnet transition occurs through the uniform magnetic state. The incommensurate phase in YMn₆Sn₆ exhibits four satellites, which are observed in the low-angle range of X-ray diffraction pattern and demonstrate different behavior with changing temperature. At 293 K, the antiferromagnet → ferromagnet transition in the Y_{1 ?x} Tb _x Mn₆Sn₆ compound can be induced by applied magnetic field, in particular, the field μ₀ H = 0.3 T induces the transition in Tb_0.15Y_0.85Mn₆Sn₆.     

Improving wear resistance of drilling tools fitted with synthetic diamond

The paper summarizes the findings of investigation of the influence of physicochemical and physical-mechanical properties of synthetic diamond grits on the drilling tool performance. Wear resistance of drilling tools is demonstrated to increase when they are fitted with synthetic diamond grits that are highly uniform in strength. The use of diamond grits with a better developed surface is found to provide a stronger grit retention in the bond and reduced drilling tool wear.     

Developmentally regulated expression of persyn, a member of the synuclein family, in skin

Synucleins constitute a group of unique, evolutionarily conserved proteins that are expressed predominantly in neurons of the central and peripheral nervous system. Although the normal cellular functions of synucleins are not clear, these proteins have been implicated in various neurodegenerative conditions in humans. We found that persyn, a recently characterized member of the synuclein family, is expressed not only in the nervous system but also in the stratum granulosum of the epidermis of neonatal and adult mice. This finding together with our recent observations that persyn influences neurofilament network integrity in sensory neurons raises the possibility that persyn in skin could be involved in modulation of the keratin network.     

Segmental antigen challenge increases fibronectin in bronchoalveolar lavage fluid

Fibronectin may contribute to asthma pathogenesis by recruitment and activation of inflammatory cells, and by promotion of subepithelial fibrosis. Fibronectin is produced by several types of airway cells, including epithelial cells, fibroblasts, and alveolar macrophages. To test the hypothesis that antigen-induced airway inflammation is associated with increased local generation of fibronectin, segmental bronchoprovocation (SBP) with antigen and saline was performed in 17 atopic patients. Bronchoalveolar lavage (BAL) was performed at 5 min and 48 h after segmental challenge with saline or antigen. Fibronectin concentrations in BAL fluid, measured by enzyme-linked immunosorbent assay (ELISA), increased more than 5-fold 48 h after antigen challenge (65 [47 to 110] versus 407 [240 to 697] ng/ml, median and 25 to 75% interquartiles, p < 0.05). Fibronectin concentrations 48 h after antigen challenge correlated with histamine concentrations 5 min after antigen challenge and numbers of eosinophils, neutrophils, macrophages, and total cells in BAL fluid 48 h after antigen challenge. BAL was more enriched in fibronectin 48 h after challenge than would be predicted solely from increased permeability of plasma proteins. Western blot analysis showed that fibronectin in BAL fluid was largely intact and contained the extra domain-A (ED-A) splice variant of cellular fibronectin, indicative of local production. We conclude that antigen challenge in atopic subjects causes increased production of fibronectin by airway cells and speculate that this response may contribute to airway remodeling in allergic inflammation.     

Obtaining gunite-bodies with the additions of the waste products of the aluminum industry

Conclusions We studied the possibility of using the waste products of the aluminum industry as additives for obtaining gunite-bodies. In order to carry out guniting of the electrolytic cells, we suggested the application of the lining-slag type systems and the systems based on corundum for improving the service life of the refractory lining of these units.Translated from Ogneupory, No. 1, pp. 8–10, January, 1990.     

Insulin therapy could prevent salt-induced high blood pressure in diabetes mellitus

The effectiveness of insulin replacement therapy in the prevention of salt-induced hypertension in diabetes mellitus was examined using Alloxan diabetic rats. Early daily (eight units/day) treatment with insulin prevented the development of high blood pressure after six weeks of high-salt feeding. The mean arterial pressure (MAP) for the early insulin-treated and salt-fed group (DET-SF) was 123.37 +/- 6.37 mmHg which was close to the value for normal (control) rats 128.17 +/- 4.84 mmHg, but significantly (p < 0.001) less than that of the untreated diabetic salt-fed group (DSF) which was 164.58 +/- 8.33 mmHg. The nondiabetic salt-fed (NDSF) group had MAP of 150.27 +/- 4.24 mmHg. Late commencement of insulin therapy did not significantly affect the sensitivity of the diabetic rats to high-salt diet. The results suggest that early commencement of insulin therapy could prevent the development of high blood pressure in diabetic rats.