Study on chemical speciation in aluminum chloride solution by ESI-Q-MS

AlCl(3) solution was analyzed at concentrations from 0.02 to 100 mM using an electrospray ionization quadrupole mass spectrometer (ESI-Q-MS), and the dissolution state of aluminum ions is discussed. Results obtained using ESI-Q-MS were consistent with those obtained using (27)Al nuclear magnetic resonance ((27)Al NMR). Aluminum species existed mainly as positively charged monomeric aluminum hydroxide coordinated with several water molecules in solution. The complexation of chloride ions by aluminum ions differed between the positive and negative ion modes. Chemical reactions that partially modified chemical forms of species through ESI-Q-MS measurement were also observed. In the same aluminum chloride solution, using ESI-TOF-MS and ESI-Q-MS/MS studies, the disagreement of the reports is discussed. It is concluded that ESI-TOF-MS might show also the gas-phase reaction in the mass spectrometer but the dissolution state of aluminum species can be shown by ESI-Q-MS.     

Effects of doping with nanoscale Co3O4 particles on the superconducting properties of powder-in-tube processed MgB2 tapes

Nanoscale Co₃O₄ particles were doped into MgB₂ tapes with the aim of developing superconducting wires with high-current-carrying capacity. Fe-sheathed MgB₂ tapes with a mono-core were prepared using the in situ powder-in-tube (PIT) process with the addition of 0.2–1.0 mol% Co₃O₄. The critical temperature decreased monotonically with an increasing amount of doped Co₃O₄ particles for all heat-treatment temperatures from 600 to 900 °C. However, the transport critical current density (J_c) at 4.2 K varied with the heat-treatment temperatures. The J_c values in magnetic fields ranging from 7 to 12 T decreased monotonically with increasing Co₃O₄ doping level for a heat-treatment temperature of 600 °C. In contrast, some improvements on the J_c values of the Co₃O₄ doped tapes were observed in the magnetic fields below 10 T for 700 and 800 °C. Furthermore, J_c values in all the fields measured increased as the Co₃O₄ doping level increase from 0 to 1 mol% for 900 °C. This heat-treatment temperature dependence of the J_c values could be explained in terms of the heat-treatment temperature dependence of the irreversibility field with Co₃O₄ doping.     

Enantioselective synthesis of methyl 2-[1-[(tert-butoxycarbonyl)amino]ethyl]-4-methyloxazole-5-carboxylate by a one–pot enamide cyclization

Methyl 2-[1-[(tert-butoxycarbonyl)amino]ethyl]-4-methyloxazole-5-carboxylate (1) was synthesized with high optical purity via a Pd–catalyzed amide coupling with vinyl triflate with subsequent oxazole formation. The latter reaction proceeds via bromination of an enamide with NBS and DBU-promoted cyclization. The oxazole subunit positional isomer in a macrocyclic azole peptide was obtained in a good yield without racemization. The scope and limitations of this reaction were also investigated.     

Effect Of Calcium Ions On The Irradiation Induced Inactivation Of Cellulase

Abstract

The activity of cellulase irradiated at various temperatures was examined as a function of irradiation dose. The effect of calcium ions in radiation inactivation of cellulase at irradiation temperature of 30°C was studied by using calcium sulfate. The calcium ions have a protective ability against radiation caused inactivation of cellulase by scavenging species such as OH^? formed by irradiation of cellulase aqueous solution, in which the effective concentration range of the calcium ions was ～ 10^?3 M. The calcium ions do not act for the heat inactivation of the enzyme and the enzyme hydrolysis of filter paper or chaff as an activator because the calcium ions do not associate with the enzyme to form a calcium ion-enzyme complex.     

Stereoselective synthesis of 1,4-bifunctional compounds by regioselective Pd-catalyzed allylic substitution reaction

[reaction: see text] Highly stereoselective synthesis of 1,4-bifunctional compounds was accomplished via 1,2-asymmetric induction to alpha-oxyaldehyde followed by regio- and diastereoselective Pd-catalyzed allylic substitution reaction.     

Mechanism of Immobilization of Enzymes by Radiation-Induced Polymerization of Glass-Forming Monomers

Immobilization of enzymes by radiation-induced polymerization has been studied at low temperatures by use of various hydrophilic and hydrophobic glass-forming monomers such as hydroxy-alkyl methacrylate and poly(ethylene glycol diacrylate). Activity yield of the immobilized enzyme depends on the monomer concentration in polymerization. In the immobilized enzymes with strongly hydrophobic matrices, the activity shows a maximum at an optimum monomer concentrations in a certain stage of repeated usage for the enzyme reaction. The decrease of activity with repeated use is very little in strongly hydrophobic systems, particularly in diethylene glycol diacrylate polymer matrices. The hydrophobic polymer-enzyme composite has the microsphere form. In the present method, a model scheme for immobilization mechanism is proposed, which is compared with that formed in the polymerization of a nonglass-forming monomer system and also by the solution polymerization at higher temperatures.