Simultaneous production of96Tc and111In by α-particle irradiation of stacked Nb and Ag foils,and their carrier-free separations

In order to produce routinely carrier-free⁹⁶Tc and¹¹¹In, their simultaneous production was examined by means of the stacked foil method. Both niobium and silver foils were arranged on the target holder so as the desired nuclear reactions took place effectively. Simultaneous irradiation of the target with 35 MeV -particles produced effectively¹¹¹In and⁹⁶Tc by the¹⁰⁹Ag(, 2n)¹¹¹In and⁹³Nb(, n)⁹⁶Tc reactions, respectively. Sufficient amounts of radioactivities for tracer uses are obtained by the irradiation at 5 A current for 2 hrs. In addition, carrier-free⁹⁶TcO₄ ^– in a perchloric acid solution could be prepared by the combined use of precipitation and anion-exchange methods. Separation of carrier-free¹¹¹In from the silver matrix was done by means of solvent extraction using acetylacetone as a chelating agent.     

Asymmetric Michael addition of a recyclable chiral amine: inversion of stereoselectivity caused by the difference of ethereal solvents

The Michael addition of a chiral amine [(-)- 6] to alpha,beta-unsaturated esters ( 4) was attained and the stereoselectivity was inverted by changing the solvent from diethyl ether to tetrahydrofuran when alpha,beta-unsaturated esters having an aromatic ring at the beta-position were employed. In addition, the chiral auxiliary in the Michael adducts ( 9A) was facilely removed with N-iodosuccinimide to afford beta-amino esters ( 10A) and 2-methoxy- d-bornylaldehyde ( 11), which can be reclaimed to the chiral amine ( 6) by reductive amination.     

Medicinal foodstuffs. XXXIV. Structures of new prenylchalcones and prenylflavanones with TNF-alpha and aminopeptidase N inhibitory activities from Boesenbergia rotunda

The methanolic extract from the rhizomes of Boesenbergia rotunda (Zingiberaceae) was found to show inhibitory effect on tumor necrosis factor-alpha (TNF-alpha)-induced cytotoxicity in L929 cells (IC(50)=6.1 microg/ml). By bioassay-guided separation, four new prenylcalcones, (+)-krachaizin A (1a), (-)-krachaizin A (1b), (+)-krachaizin B (2a), and (-)-krachaizin B (2b), and four new prenylflavanones, rotundaflavones Ia (3a), Ib (3b), IIa (4a), and IIb (4b), were isolated together with 18 known constituents (5a-7b and 8-19). The structures of eight new compounds were elucidated on the basis of physicochemical evidence. Among them, (+)-krachaizin B (2a), (-)-krachaizin B (2b), (+)-4-hydroxypanduratin A (6a), (-)-4-hydroxypanduratin A (6b), (+)-isopanduratin A (7a), (-)-isopanduratin A (7b), alpinetin (10), cardamonin (14), and 2,6-dihydroxy-4-methoxydihydrochalcone (15) significantly inhibited TNF-alpha-induced cytotoxicity in L929 cells at 10 microM. In addition, 2a, 2b, (+)-panduratins A (5a), (-)-panduratin A (5b), 6a, 7b, and geranyl-2,4-dihydroxy-6-phenylbenzoate (17) were found to show strong inhibitory effects on aminopeptidase N activity.     

Structure-based engineering of a plant type III polyketide synthase: formation of an unnatural nonaketide naphthopyrone

Pentaketide chromone synthase (PCS) from Aloe arborescens is a novel plant-specific type III polyketide synthase (PKS) that produces 5,7-dihydroxy-2-methylchromone from five molecules of malonyl-CoA. On the basis of the crystal structures of wild-type and M207G mutant PCS, the F80A/Y82A/M207G triple mutant was constructed and shown to produce an unnatural novel nonaketide naphthopyrone by sequential condensations of nine molecules of malonyl-CoA. This is the first demonstration of the formation of a nonaketide by the structurally simple type III PKS. A homology model predicted that the active-site cavity volume of the triple mutant is increased to 4 times that of the wild-type PCS.     

Simulations of Two-Dimensional Photon Scanning Tunneling Microscope by Boundary Integral Equation Method: p-polarization

Accurate simulations of a two-dimensional photon scanning tunneling microscope (2D-PSTM) for incident p-polarized waves (TM-mode) have been performed by the boundary integral equations called guided-mode extracted integral equations. The method used in this paper is a global method and the case of uncoated dielectric probe is treated. Complete and rigorous integral equations for a given configuration of 2D-PSTM have been solved numerically by the conventional boundary-element method with high accuracy. Using three universal laws, i.e., the optical theorem, the energy conservation law and the reciprocity relation for incident p-polarized waves, numerical results have been confirmed. The basic physical characteristics of interaction between probe-tip and near-field for incident p-polarized waves are compared in detail with those of incident s-polarized waves (TE-mode) which are previously reported.This paper was originally presented at the 5th International Conference on NEAR FIELD OPTICS and RELATED TECHNOLOGIES(NFO-5), which was held on December 6–10, 1998 at Coganoi Bay Hotel, Shirahama, Japan, in cooperation with the Japan Society of Applied Physics and Mombusho Grant-in Aid for Scientific Research on Priority Areas “Nearfield Nano-optics” Project, sponsored by Japan Society for the Promotion of Science.