AES studies on the Ti/N compositionally gradient film deposited onto Ti-6Al-4V alloy by reactive DC sputtering.

Deposition of Ti/N compositionally gradient film onto Ti-6Al-4V alloy substrates was carried out by reactive DC sputtering, not only to improve the blood compatibility of the alloy but also to relax the stress concentrated at the interface between the film and the alloy substrate. The compositional gradient was realized by varying continuously the nitrogen content in Ar-N2 sputter gas during deposition. In Auger electron spectroscopy (AES) analysis, Auger spectra were acquired in the N(E) mode using the beam brightness modulation (BBM) method to overcome the problem of the peak overlap of the principal Auger nitrogen transition peak (N-KLL) with one of titanium peaks (Ti-LMM). The deposited film appeared to be uniform and adhesive. TiN formation at the surface of the film was assumed, because of its yellow gold color and the X-ray diffraction (XRD) pattern for it. Under scanning electron microscopy, it was found that the surface had fine particles dispersed on a smooth accumulated deposit and that this depositing method improved the structural property of the film at the surface. According to AES in-depth profiles, the nitrogen (N) concentration in the film gradually decreased in the depth direction from the surface toward the alloy, confirming that a Ti/N compositionally gradient film had formed on the alloy substrate.     

Effects of fullerene substituents on structure and photoelectrochemical properties of fullerene nanoclusters electrophoretically deposited on nanostructured SnO2 electrodes

Two kinds of fullerene derivatives have been designed to examine the effect of the fullerene substituents on the structure and photoelectrochemical properties of fullerene clusters electrophoretically deposited on nanostructured SnO(2) electrodes. The cluster sizes increase and the incident photon-to-current efficiencies decrease with introduction of large substituents into C(60). The trend for photocurrent generation efficiency as well as surface morphology on the electrode can be explained by the steric bulkiness around the C(60) molecules. A C(60) molecule with two alkoxy chains is suggested to give a bilayer vesicle structure, irrespective of the hydrophobic nature of both the C(60) and alkoxy chain moieties. Such information will be valuable for the design of photoactive molecules, which are fabricated onto electrode surfaces to exhibit high energy conversion efficiency.     

The Kα and Kβ X-ray spectra of Al,Ti, Cr,Fe and Ni induced by 84 MeV nitrogen ions

The K X-rays from the target elements due to N-ion bombardment are measured with a crystal spectrometer. Some aspects owing to high incident energy are discussed. The Kα satellite, Kα hypersatellite and Kβ satellite peak spacings are obtained.     

On-chip electrochemical measurement of beta-galactosidase expression using a microbial chip

[small beta]-Galactosidase expression in a small number of Escherichia coli cells has been measured in real time with an electrochemical sensor chip. E. coli cells were embedded using collagen gel within a micropore which was microfabricated onto a chip. The activity of the expressed [small beta]-galactosidase was determined using p-aminophenyl [small beta]-d-galactopyranoside (PAPG) as a substrate.     

Synthesis and evaluation of 1-arylsulfonyl-3-piperazinone derivatives as a factor Xa inhibitor II. Substituent effect on biological activities

Intravascular clot formation is an important event in a number of cardiovascular diseases. The prevention of blood coagulation has become a major target for new therapeutic agents. Factor Xa (FXa) is a trypsin-like serine protease that plays a key role in the blood coagulation cascade and represents an attractive target for anticoagulant drug development. We have investigated substituents in the central part of a lead compound (3: M55113), and discovered that compound M55551 (34: (R)-4-[(6-Chloro-2-naphthalenyl)sulfonyl]-6-oxo-1-[[1-(4-pyridinyl)-4-piperidinyl]methyl]-2-piperazinecarboxylic acid) is a potent inhibitor of FXa (IC(50)=0.006 microM), with high selectivity for FXa over trypsin and thrombin. The activity of this compound is ten times more powerful than the lead compound.     

A Strategy for Neuraminidase Inhibitors Using Mechanism‐Based Labeling Information

A potent inhibitor for Vibrio cholerae neuraminidase (VCNA) was developed by using a novel two‐step strategy, a target amino acid validation using mechanism‐based labeling information, and a potent inhibitor search using a focused library. The labeling information suggested the hidden dynamics of a loop structure of VCNA, which can be a potential target of the novel inhibitor. A focused library composed of 187 compounds was prepared from a 9‐azide derivative of 2,3‐dehydro‐N‐acetylneuraminic acid (DANA) to interrupt the function of the loop of the labeled residues. Inhibitor 3c showed potent inhibition properties and was the strongest inhibitor with FANA, a N‐trifluoroacetyl derivative of DANA. Validation studies of the inhibitor with a detergent and a Lineweaver–Burk plot suggested that the 9‐substitution group would interact hydrophobically with the target loop moiety, adding a noncompetitive inhibition property to the DANA skeleton. This information enabled us to design compound 4 having the combined structure of 3c and FANA. Compound 4 showed the most potent inhibition (K_i=73 nM , mixed inhibition) of VCNA with high selectivity among the tested viral, bacterial, and mammal neuraminidases.     

Depression of Disproportionation of π-Radical Anion of Gold Porphyrin Electrostatically Fixed in a Polymer Matrix

The electrochemical and photochemical reduction of the fully methylated derivative of gold meso-tetrakis-(4-pyridyl)porphine (AuTMPyP) in homogeneous solution gives not only a π-radical anion but also its successive product, phlorin, by disproportionation. The electrostatic fixation of AuTMPyP in a Nafion matrix inhibits the latter undesired reaction against effective charge separation, which is explained by the diffusion constant lower by 8 order of magnitude during electrolytic reduction of AuTMPyP compared to that in homogeneous aqueous solution.     

Synthesis of End-Reactive Polymers with Controlled Molecular Weight by Metalloporphyrin Catalyst

α, β, γ δ-Tetraphenylporphinatoaluminum carboxylate (TPPA10COR) and phenoxide (TPPA10Ar) bring about the polymerization of β-lactone and epoxide to give polymers with controlled chain length having a carboxylic ester or phenoxy group at the end of each polymer molecule. Acrylate (TPPA10COCH=CH2) and p-vinylphenoxide (TPPA1-OC₆H₄,CH[dbnd]CH₂ (p)) as initiator give polyester or polyether macromer with narrow molecular weight distribution.     

Electrochemical monitoring of intracellular enzyme activity of single living mammalian cells by using a double-mediator system

We evaluated the intracellular NAD(P)H:quinone oxidoreductase (NQO) activity of single HeLa cells by using the menadione–ferrocyanide double-mediator system combined with scanning electrochemical microscopy (SECM). The double-mediator system was used to amplify the current response from the intracellular NQO activity and to reduce menadione-induced cell damage. The electron shuttle between the electrode and menadione was mediated by the ferrocyanide/ferricyanide redox couple. Generation of ferrocyanide was observed immediately after the addition of a lower concentration (10 μM) of menadione. The ferrocyanide generation rate was constant for 120 min. At a higher menadione concentration (100 μM), the ferrocyanide generation rate decreased within 30 min because of the cytotoxic effect of menadione. We also investigated the relationship between intracellular reactive oxygen species or glutathione levels and exposure to different menadione concentrations to determine the optimal condition for SECM with minimal invasiveness. The present study clearly demonstrates that SECM is useful for the analysis of intracellular enzymatic activities in single cells with a double-mediator system.