Direct proline-catalyzed asymmetric alpha-aminoxylation of aldehydes and ketones

The direct proline-catalyzed asymmetric alpha-aminoxylation of aldehydes and ketones has been developed using nitrosobenzene as an oxygen source, affording alpha-anilinoxy-aldehydes and -ketones with excellent enantioselectivity. Reaction conditions have been optimized, and low temperature (-20 degrees C) was found to be a key for the successful alpha-aminoxylation of aldehydes, while slow addition of nitrosobenzene is essential for that of ketones. The scope of the reaction is presented.     

Determination of technetium-99 and neptunium-237 in environmental samples by inductively coupled plasma mass spectrometry

New analytical techniques using Inductively Coupled Plasma Mass Spectrometry (ICP-MS) were applied to the determination of technetium-99 (Tc-99) and neptunium-237 (Np-237) in environmental samples. The determination of Tc-99 consists of a cyclohexanone solvent extraction method to eliminate the interference isobar (Ru-99). An anion exchange with acetic acid media and a TTA-xylene solvent extraction were used for the determination of Np-237. Technetium-95m and Np-239 were used as chemical recovery tracers in these methods. The concentrations of Tc-99 and Np-237 in the typical surface soil samples in Japan ranged form 8.1×10² to 1.8×10^–1 Bq/kg-dry, from 3.3×10^–3 to 8.0×10^–3 Bq/kg-dry, respectively.     

Molecular dynamics simulation of papain-E-64 (N-[N-(L-3-trans-carboxyoxirane-2-carbonyl)-L-leucyl]agmatine) complex

To investigate the possible binding mode of E-64 (N-[N-(L-3-trans-carboxyoxirane-2-carbonyl)-L-leucyl]agmatine), a potent cysteine protease inhibitor, to papain active site, molecular dynamics simulations were applied to two complex forms: R- and S- configurational forms of E-64 C2 atom for the covalent bond formation with the papain Cys-25 SH group. The tertiary structures of the papain-E-64 complexes were built by visual interactive modelling and the energy minimization technique, and were subjected to the dynamics simulations of 10 ps. Although no significant difference was observed between the potential energies of energy-minimized R- and S-complex forms, the molecular dynamics simulations suggested that the hydrogen bonding mode of the former form is more advantageous than that of the latter one. Comparing with the hydrogen bonds observed in the papain-E-64 complex crystal, it could be concluded that the present molecular dynamics simulation reflects well the three-dimensional structure concerning the interaction of E-64 with the papain active site. The conformational characteristics of E-64 and its possible interaction mode with papain were also discussed.     

Ground states of a modified symmetric Anderson lattice in one dimension

Based on a previous exact solution of a one-dimensional symmetric Anderson lattice the energy distributions of pseudo-densities of states and the energies of localized and conduction electrons in singlet ground states are calculated. The Kondo-lattice temperature T_KL is obtained as T_KL ≈ (1/2 πUV²)^1/2exp(-/U/2V²) +1/4 πUV².     

Production of123I using the CV-28 cyclotron at IPEN-CNEN/SP

These studies had the purpose of establishing the optimal conditions for the production of¹²³I through the¹²⁴Te (p, 2n)¹²³I reaction, using the CV-28 Cyclotron (E_max=24 MeV for protons) at IPEN-CNEN/SP. Two different targets (TeO₂ and TeO₂+2% Al₂O₃) were irradiated in order to check their physical resistance against beam current (up to 12 A) and length of irradiation (10 min — 2h), and to evaluate the recovery of the radioiodine produced, by a dry distillation process with a high frequency induction furnace. Later on, enriched¹²⁴TeO₂ (96.2%) targets were irradiated, and¹²³I was produced routinely with a production yield of (3. 31±0.07) mCi/Ah, 1.7% of¹²⁴I at EOB and radiochemically pure.