The thermolysin-catalyzed condensation reactions of n-substituted aspartic and glutamic acids with phenylalanine alkyl esters

The title reactions occur with concurrent peptide synthesis and optical resolutions of racemic substrates. With this method, Z-L-Asp-L-Phe-OME, the precursor to the synthetic sweetner, could be obtained in high yield.     

Side chain-directed complementary cis-coordination of two pyridines on Pd(II): Selective multicomponent assembly of square-, rectangular-, and trigonal prism-shaped molecules

This paper describes a new strategy to regulate multicomponent assembly from two kinds of pyridine-based ligands and cis-protected Pd(II) ions. The introduction of sterically hindered substituents to only one of the two ligands directs the complementary cis-coordination of the two lingads on the Pd(II) center, leading to the selective multicomponent assembly of two- and three-dimensional polynuclear Pd(II) complexes (e.g., square-, rectangular-, and trigonal prism-shaped molecules).     

Image contrast analysis of STM images of self-assembled dioctadecyl chalcogenides on graphite at the liquid-solid interface.

The structures of self-assembled monolayers of dioctadecyl selenide (CH3(CH2)17)2Se and dioctadecyl telluride (CH3(CH2)17)2Te, as well as dioctadecyl ether (CH3(CH2)17)2O and dioctadecyl sulfide (CH3(CH2)17)2S, on graphite at the liquid-solid interface were systematically investigated by scanning tunneling microscopy (STM). Both dioctadecyl selenide and telluride formed monolayer structures in which the tilt angle between the molecular axis of the alkyl chain and the lamellae axis was 90 degrees , while dioctadecyl ether assembled with a tilt angle of 60 degrees . Dioctadecyl sulfide was found to make two different self-assembled structures having tilt angles of 60 and 90 degrees . When selenide was embedded in ether compounds in mixed self-assembled monolayers, the alkyl chains of the selenide became blurred, implying that the alkyl chains in the monolayers were unstable. This is in contrast with the structure of co-adsorbed monolayers of the ether and sulfide compounds, where the images of all alkyl chains had high spatial resolution. For the co-adsorbed monolayers, the image contrast of chalcogen atoms was normalized compared with that of alkyl chains of the ether compound in the same image frame. The normalized image contrast was found to be independent of the measurement conditions involving tip shapes, having the following trend, Te>Se>S>C>O. The difference in the normalized image contrast among chalcogen atoms are discussed based on fundamental parameters like polarizability and atomic radii.     

Theoretical insights into the formation, structure, and electronic properties of anticancer oxaliplatin drug and cucurbit[n]urils n = 5 to 8

Geometries, formation and electronic properties of cucurbit[n]uril-oxaliplatin n = 5–8, host-guest complexes are investigated with DFT calculations. The formation of inclusion complexes of CB[n]-oxaliplatin are facile in CB[n] n = 6–8. In the complex, the cyclohexyl group is found to be deep inside the cavity, with the formation of a hydrogen bonding between the portal oxygen atoms and the amine nitrogen of the oxaliplatin guest. NBO analysis shows the transfer of charge from the metal center to the CB[7] unit and the existence of hydrogen bonding between the oxygen portal and amine nitrogen. The HOMO orbital is localized on the carboxylate group and the LUMO orbital are localized on the cucurbituril unit in CB[7]-oxaliplatin complex. The strength of the interaction determined here reflects the ability of CB[n] to act as a host for suitably oxaliplatin guests, even in aqueous solution.     

Synthesis and evaluation of novel 2-oxo-1,2-dihydro-3-quinolinecarboxamide derivatives as serotonin 5-HT4 receptor agonists

A series of N-azabicycloalkyl-1-alkyl-2-oxo-1,2-dihydro-3-quinolinecarboxamides were synthesized and tested for serotonin 5-HT4 receptor-stimulating effects in the regulation of electrically-evoked contraction in guinea pig muscle. Among them, N-azabicycloalkyl-1-isopropyl-2-oxo-1,2-dihydro-3-quinolinecarboxamide (8c, 9c, 10c, 11c, 12c) exhibited potent serotonin 5-HT4 receptor-stimulating activity. The most potent compound, N-(endo-8-methyl-8-azabicyclo[3.2.1 oct-3-yl)-1-isopropyl-2-oxo-1,2-dihydro-3-quinolinecarboxamide (8c, ED50 = 36.3 nMi), was seven times as active as cisapride, while 8c had no affinity for 5-HT1A, 5-HT1D, D2, muscarinic M2 or muscarinic M3 receptors even at 10 microM. Compound 8c stimulated digestive tract motility in conscious fed dogs (1.0 mg/kg p.o.).     

Control of shell thickness in silica-coating of Au nanoparticles and their X-ray imaging properties

This paper describes a performance of precise control of shell thickness in silica-coating of Au nanoparticles based on a sol-gel process, and an investigation into X-ray imaging properties for the silica-coated Au (Au/SiO(2)) particles. The Au nanoparticles with a size of 16.9±1.2 nm prepared through a conventional citrate reduction method were used as core particles. The Au nanoparticles were silica-coated with a sol-gel reaction using tetraethylorthosilicate (TEOS) as a silica source, sodium hydroxide (NaOH) as a catalyst, and (3-aminopropyl) trimethoxysilane (APMS) as a silane coupling agent. An increase in TEOS concentration resulted in an increase in shell thickness. Under certain concentrations of Au, H(2)O, NaOH, and APMS, the Au/SiO(2) particles with silica shell thickness of 6.0-61.0 nm were produced with varying TEOS concentration. Absorption peak wavelength of surface plasmon resonance of the Au/SiO(2) colloid solution depended on silica shell thickness, which agreed approximately with the predictions by Mie theory. The as-prepared colloid solution could be concentrated up to an Au concentration of 0.19 M with salting-out and centrifugation. The concentrated colloid solution showed an X-ray image with high contrast, and a computed tomography value for the colloid solution with an Au concentration of 0.129 M was achieved 1329.7±52.7 HU.     

Thermal simulation and analysis of the STF cryomodule

STF is a superconducting RF test facility constructed at the high energy accelerator research orga-nization of Japan (KEK), as a main part of a R&D project for the proposed International Linear Collider (ILC) in Asia. Thermal study of the STF 1.3 GHz 9-cell cavity cryomodule was carried out within a collaboration between China and Japan. Static and dynamic thermal behaviors of the STF cryomodule were simulated and analyzed with the FEM method, and some simulation results were compared with the available experimental data. This paper presents the details.