Metastable high-pressure phases of low-Z compounds: creation of a new chemistry or a prompt for old principles?

Recent experiments demonstrate that high pressure is a powerful tool for the synthesis of new unusual inorganic polymers consisting of low-Z elements. However, experience within organic chemistry, for example, polyethylene, provides evidence that polymeric phases with high thermal stability can be potentially synthesised by conventional chemical techniques without applying high pressure.     

A G protein gamma subunit-like domain shared between RGS11 and other RGS proteins specifies binding to Gbeta5 subunits

Regulators of G protein signaling (RGS) proteins act as GTPase-activating proteins (GAPs) toward the alpha subunits of heterotrimeric, signal-transducing G proteins. RGS11 contains a G protein gamma subunit-like (GGL) domain between its Dishevelled/Egl-10/Pleckstrin and RGS domains. GGL domains are also found in RGS6, RGS7, RGS9, and the Caenorhabditis elegans protein EGL-10. Coexpression of RGS11 with different Gbeta subunits reveals specific interaction between RGS11 and Gbeta5. The expression of mRNA for RGS11 and Gbeta5 in human tissues overlaps. The Gbeta5/RGS11 heterodimer acts as a GAP on Galphao, apparently selectively. RGS proteins that contain GGL domains appear to act as GAPs for Galpha proteins and form complexes with specific Gbeta subunits, adding to the combinatorial complexity of G protein-mediated signaling pathways.     

Recurrent Meesmann''s corneal epithelial dystrophy after penetrating keratoplasty

Endoscopic treatment of chronic pancreatitis has drawn benefits from endoscopic procedures previously described for the main bile duct. Endotherapy is developing throughout the world. Cyst drainage procedures certainly represent the largest step forward in that non-surgical approach, whatever it is either direct (through the stomach or the duodenum) or indirect through the papilla in the duodenum. This procedure gives similar results to surgery with a lower morbidity. Pancreatic duct drainage associated with stone clearance is feasible and provides good results which have not yet been compared with those obtained thanks to surgery. Nonetheless, when the duct is not widely dilated it has been proven to be a satisfactory alternative to surgery. By contrast, chronic cholestasis does not appear to be a good indication of endotherapy.     

Hydrogen bonding at the active site of delta 5-3-ketosteroid isomerase

The solution secondary structure of the highly active Y55F/Y88F "Tyr-14-only" mutant of delta 5-3-ketosteroid isomerase complexed with 19-nortestosterone hemisuccinate has been shown to consist of three helices, a six-stranded mixed beta-sheet, and five turns. The steroid binds near the general acid, Tyr-14, on helix 1, near the general base, Asp-38, on the first strand of the beta-sheet, and on the hydrophobic face of the beta-sheet [Zhao, Q., Abeygunawardana, C., & Mildvan, A. S. (1997) Biochemistry 36, 3458-3472]. On this hydrophobic face, Asp-99 is the only polar residue. Free isomerase shows a deshielded exchangeable proton resonance at 13.1 ppm assigned to the N epsilon H of neutral His-100. Its fractionation factor (phi = 0.79) and slow exchange with solvent suggest it to be buried or involved in an H-bond. The binding of dihydroequilenin or estradiol to isomerase induces the appearance of two additional deshielded proton resonances, one at 18.2 ppm assigned to the gamma-carboxyl proton of Asp-99, and the other, at 11.6 ppm, assigned to the zeta-OH proton of Tyr-14. While mutation of Asp-99 to Ala results in the disappearance of only the resonance near 18 ppm [Wu, R. W., Ebrahemian, S., Zwrotny, M. E., Thornberg, L. D., Perez-Alverado, G. C., Brothers, P., Pollack, R. M., & Summers, M. F. (1997) Science 276, 415-418], both of these resonances disappear in mutants lacking Tyr-14, suggesting an H-bonded catalytic diad, Asp-99-COOH--Tyr14-OH--O-steroid enolate. The catalytic diad is further supported by NOEs from the beta 1 and beta 2 protons of Asp-99 to the epsilon protons of Tyr-14, and from the zeta-OH proton of Tyr-14 to the gamma-carboxyl proton of Asp-99, indicating close proximity of these two residues, and by other data from the literature. A strong, low-barrier H-bond between Asp-99 and Tyr-14 is indicated by the 6.2 ppm deshielding, low fractionation factor (phi = 0.34) and slow exchange of the resonance at 18.2 ppm. A normal H-bond between Tyr-14 and the steroid is indicated by the 1.8 ppm deshielding, fractionation factor of 0.97 and the slow exchange of the resonance at 11.6 ppm. It is suggested that the 10(4.7)-fold contribution of Tyr-14 to catalysis is made possible by strong H-bonding from Asp-99 in the catalytic diad which strengthens general acid catalysis by Tyr-14. It is also noted that highly deshielded proton resonance on enzymes between 15 and 20 ppm, assigned to low-barrier H-bonds, generally involve carboxyl groups.     

Radon daughter deposition velocities estimated from field measurements

The surface deposition rate (plateout) of unattached radon daughters was estimated from simple surface activity measurements in a number of occupied buildings, and found to be about one third of the lowest value measured in diffusion tube experiments. This low value was confirmed by surface deposition and activity measurements made in a commercial building with high radon levels, which also showed that the deposition rate was higher on walls than on floors or tables. Predictions of the ratio between airborne and surface-deposited radon daughter activity using the estimated surface deposition rate were close to the ratios observed in occupied homes. Refinements to existing models are required to explain the variability of deposition rate with surface orientation.     

New technological solutions to protect the lining of blast-furnace hearths

The use of schungite as a partial replacement for coke is practiced in Russia at a number of metallurgical plants, both in the production of foundry iron (its primary use) and in making conversion pig iron. The largest amount of coke is replaced when foundry iron is being made, the replacement coefficient in this case having a value within the range 0.8–1.3. Studies that included continuous monitoring of the temperature of the carbon blocks in blast furnaces with volumes of 1719, 3200, and 5580 m³ unambiguously demonstrate that the thickness of the slag crust in blast furnaces increases with the use of schungite. Protecting the lining of the hearth through the use of schungite is also accompanied by a decrease in coke consumption. __________ Translated from Metallurg, No. 8, pp. 53–57, August, 2007.     

Specific recognition of HLA-E, but not classical, HLA class I molecules by soluble CD94/NKG2A and NK cells

The CD94/NKG2 receptors expressed by subpopulations of NK cells and T cells have been implicated as receptors for a broad range of both classical and nonclassical HLA class I molecules. To examine the ligand specificity of CD94/NKG2 proteins, a soluble heterodimeric form of the receptor was produced and used in direct binding studies with cells expressing defined HLA class I/peptide complexes. We confirm that CD94/NKG2A specifically interacts with HLA-E and demonstrate that this interaction is dependent on the association of HLA-E with peptide. Moreover, no interaction between CD94/NKG2A and classical HLA class I molecules was observed, as assayed by direct binding of the soluble receptor or by functional assays using CD94/NKG2A+ NK cells. The role of the peptide associated with HLA-E in the interaction between HLA-E and CD94/NKG2A was also assessed. All class I leader sequence peptides tested bound to HLA-E and were recognized by CD94/NKG2A. However, amino acid variations in class I leader sequences affected the stability of HLA-E. Additionally, not all HLA-E/peptide complexes examined were recognized by CD94/NKG2A. Thus CD94/NKG2A recognition of HLA-E is controlled by peptide at two levels; first, peptide must stabilize HLA-E and promote cell surface expression, and second, the HLA-E/peptide complex must form the ligand for CD94/NKG2A.