Enantioselective Total Synthesis of (+)‐Gephyrotoxin 287C

Gephyrotoxin 287C, a bioactive alkaloid bearing a perhydropyrrolo[1,2‐a]quinoline skeleton with five stereocenters, is an attractive target for synthetic organic chemistry. We achieved an enantioselective total synthesis of (+)‐gephyrotoxin 287C, for which the key steps were palladium‐catalyzed asymmetric allylic amination using a chiral diaminophosphine oxide (DIAPHOX) preligand, diastereoselective intramolecular Mannich reaction, and tin tetrachloride‐catalyzed diastereoselective conjugate addition/protonation.

     

Structure of the zinc endoprotease from Streptomyces caespitosus

A zinc endoprotease produced by Streptomyces caespitosus (ScNP) specifically hydrolyzes the peptide bond at the imino side of aromatic residues and is the smallest protease found to date. Although ScNP carries the zinc-binding sequence HEXXH, its primary structure of 132 amino acid residues differs from those of other known zinc metalloendoproteases. X-ray structural analysis of ScNP at 1.6 A resolution revealed that despite a lack of sequence homology, the common topological feature of main-chain folding and a beta-turn containing methionine, which is a feature of the zinc metalloendoprotease superfamily of metzincins, is conserved in ScNP. The zinc atom of ScNP is tetrahedrally ligated by the two histidines in the HEXXH sequence, an aspartate residue and a water molecule. Thus, ScNP represents a novel subfamily of metzincins with a HEXXHXXGXXD zinc-binding sequence. A plausible substrate recognition pocket to which aromatic residues bind is located near the catalytic zinc ion.     

Preliminary investigation on the sodium fast reactor concave cores with near-zero or negative sodium void reactivity

A preliminary investigation on the sodium fast reactor (SFR) concave cores was conducted with the aim of obtaining near-zero or negative sodium void reactivity (SVR). The geometry of the MOX fueled 750 MWe Japanese Sodium Fast Reactor (JSFR) core is transformed into concave cores by maintaining the same power level and heavy metal fuel inventory. The inner and outer core (with axial blanket in the lower part) configuration is maintained as in the original JSFR but the height of the inner core was set lower than the outer core to improve the SVR. Also a short inner blanket (20 cm thick) is inserted into the inner core for the same purpose. Radial blanket with the same height is also adopted as in the original JSFR to maintain the breeding ratio. In this investigation, the MOX fuel composition for the fresh fuel does not contain minor actinides. JOINT-FR code system with JENDL-4.0 library is used for neutronics, burnup, kinetics parameters as well as temperature and SVR calculations in 2-D R-Z geometry multigroup diffusion approximation. Several candidates of concave cores with favorable near-zero or negative SVR have been found whose burnup performance is comparable with the original JSFR core.     

A Study of the High-Temperature Strength of Titanium Alloys Using Nanoindentation and Micro-cantilever Bending Tests

Metallurgical and Materials Transactions A - To investigate the microscale plastic behavior of Ti-6Al-4V, Ti-6242S, and IMI-834 titanium alloys in high-temperature environment, nanoindentation and...     

Optimizing the Performance of the Meso-Scale Continuous-Flow Photoreactor for Efficient Photocatalytic CO2 Reduction with Water Over Pt/TiO2/RGO Composites

Catalysis Letters - Tuning the reaction parameters to maximize products yield is one of the major needs for any process. The goal of this research is to increase the reduction of CO2 with water by...     

Pressure-assisted capillary electrophoresis mass spectrometry using combination of polarity reversion and electroosmotic flow for metabolomics anion analysis

We have developed a method based on capillary electrophoresis (CE) coupled to mass spectrometry (MS) that is a powerful tool for metabolome analysis. In this paper, a simple method for the simultaneous analysis of anionic metabolites such as sugar phosphates, organic acids, nucleotides and CoA compounds based on pressure-assisted capillary electrophoresis coupled to electrospray ionization mass spectrometry (PACE/ESI-MS) is described. The feature of this method is that CE polarity, where the inlet of the capillary is at the anode and the outlet at the cathode, is inverted from conventional CE analysis for anions. Moreover, an ordinary fused silica capillary was chosen instead of a specific cationic polymer-coated capillary (SMILE (+) capillary). A robust and inexpensive analytical method was established from the above-mentioned CE polarity and noncoated fused silica capillary. A trimethylamine acetate electrolyte, pH 10.0, provides a high resolution between isomers. Electrolyte flow using an air pump after electrophoresis enables the comprehensive and simultaneous analyses of sugar phosphates, organic acids, nucleotides and a CoA compound that to date have been impossible to analyze. Our method can be used as a de facto standard for metabolome analysis.     

Natural convective heat transfer in uniformly heated vertical pipe annuli

Natural convective heat transfer in vertical concentric pipe annuli is investigated both numerically and experimentally for a fluid having a Prandtl number of 0.7. Numerical calculations for three cases of different heating conditions for pipes (heated inner pipe, heated outer pipe, both pipes heated) are made of laminar flows for different inner‐to‐outer‐pipe diameter ratios d_i/d_o from 0.2 to 0.8. For each case, the thermal entrance length x/b at the modified Grashof numbers Gr^*=10² to 5 × 10⁵ is well correlated with Grashof number Gr^* and annulus length to clearance ratio L/b. Local Nusselt numbers Nu_i and Nu_o in the thermally fully developed region have certain constant values dependent on the diameter ratio d_i/d_o, regardless of Gr^* and L/b. Average Nusselt numbers Nu_i and Nu_o in the thermal entrance region are also independent of Gr^* and L/b. © 2001 Scripta Technica, Heat Trans Asian Res, 30(8): 676–688, 2001