Comparative studies on the analysis of glycosylation heterogeneity of sialic acid-containing glycoproteins using capillary electrophoresis

Frontal affinity chromatography is a method for quantitative analysis of biomolecular interactions. We reinforced it by incorporating various merits of a contemporary liquid chromatography system. As a model study, the interaction between an immobilized Caenorhabditis elegans galectin (LEC-6) and fluorescently labeled oligosaccharides (pyridylaminated sugars) was analyzed. LEC-6 was coupled to N-hydroxysuccinimide-activated Sepharose 4 Fast Flow (100 μm diameter), and packed into a miniature column (e.g., 10×4.0 mm, 0.126 ml). Twelve pyridylaminated oligosaccharides were applied to the column through a 2-ml sample loop, and their elution patterns were monitored by fluorescence. The volume of the elution front (V) determined graphically for each sample was compared with that obtained in the presence of an excess amount of hapten saccharide, lactose (V₀); and the dissociation constant, K_d, was calculated according to the literature [K. Kasai, Y. Oda, M. Nishikawa, S. Ishii, J. Chromatogr. 376 (1986) 33]. This system also proved to be useful for an inverse confirmation; that is, application of galectins to an immobilized glycan column (in the present case, asialofetuin was immobilized on Sepharose 4 Fast Flow), and the elution profiles were monitored by fluorescence based on tryptophan. The relative affinity of various galectins for asialofetuin could be easily compared in terms of the extent of retardation. The newly constructed system proved to be extremely versatile. It enabled rapid (analysis time 12 min/cycle) and sensitive (20 nM for pyridylaminated derivatives, and 1 μg/ml for protein) analyses of lectin–carbohydrate interactions. It should become a powerful tool for elucidation of biomolecular interactions, in particular for functional analysis of a large number of proteins that should be the essential issues of post-genome projects.     

Immobilization of ultra-thin layer of monoclonal antibody on glass surface

When preparing an affinity column and a biosensor, it is desirable to immobilize a unimolecular layer of pure protein on a matrix. In this work, we tried to immobilize a monoclonal antibody on a surface of a glass test-tube as a model, to confirm the stability of this ultra-thin layer by an enzyme immunoassay, and to estimate the thickness of the layer on a slide glass by Fourier transform infrared reflection spectrometry. A new test-tube was washed and dried. The tube was filled with 5% 3-aminopropyltriethoxysilane. The 3-aminopropylsilylated surface was treated with glutaraldehyde and 5.6.10(-2) mg/ml solution of a normal mouse monoclonal antibody. The Schiff base between glutaraldehyde and the antibody was further reduced with 7.9.10(-3)% NaBH4. The tube was washed with 0.05% Tween 20 to block non-specific binding. The antibody immobilized on the surface was measured by an enzyme immunoassay based on a reaction of anti-mouse immunoglobulin G labelled with alkaline phosphatase, with which p-nitrophenol was produced from p-nitrophenylphosphate as a substrate. Meanwhile, various amounts of the antibody were immobilized on slide glasses in the same manner. The antibody on each surface was measured by Fourier transform infrared reflection spectrometry. The antibody immobilized under the final conditions was detectable by the enzyme immunoassay, and stable at 4 degrees C for ten days. The antibody on the slide glass was a unimolecular layer, as judged from the Fourier transform infrared spectra referred to -CONH- band semiquantitatively. Thus, we found the optimal conditions for immobilizing an ultra-thin layer of the monoclonal antibody on the glass surface.(ABSTRACT TRUNCATED AT 250 WORDS)     

Charge Transfer Between Oxygen and Zirconia

The extent of the surface charge, that develops during oxidation of zirconia, is determined using work function measurements for both bulk specimen and thin films. The bulk specimen of yttria-doped zirconia (10 mol%) exhibits maxima of the surface electrical effect at 373 and 973 K (130 and 280 mV, respectively) that can be considered in terms of oxygen chemisorption and oxygen non-stoichiometry. Thin film of undoped zirconia exhibits a maximum at 473 K (260 eV). Addition of yttria (10 mol%) to the thin film results in a substantial reduction of the maximum, to about 140 eV, that is shifted up to 600 K.This revised version was published online in November 2005 with corrections to the Cover Date.     

On the uniform asymptotic stability for a linear integro-differential equation of Volterra type

In this paper, we give a necessary and sufficient condition on the uniform asymptotic stability of the zero solution of a linear integro-differential equation of Volterra type where the ordinary part is ax(t). We put emphasis on the case a>0. The proofs of our results are carried out by using the root analysis of the characteristic equation. In Section 5 we give some conjectures.     

Growth of polar axis oriented tetragonal Pb(Zr,Ti)O3 films on CaF2 substrates with transparent (La0.07Sr0.93)SnO3

Epitaxial (La_0.07Sr_0.93)SnO₃ [LSSO] films were deposited on CaF₂ substrates by pulse laser deposition. The (1 0 0)_c orientation of LSSO films was observed only on (1 1 0)CaF₂, whereas (1 1 0)_c orientation was found on (1 1 1)CaF₂ and (1 0 0)CaF₂. (0 0 1) polar axis oriented tetragonal Pb(Zr_0.35Ti_0.65)O₃ films were grown on the fabricated (1 0 0)_cLSSO∥(1 1 0)CaF₂ by pulsed metal organic chemical vapor deposition. The (0 0 1)Pb(Zr_0.35Ti_0.65)O₃∥(1 0 0)cLSSO∥(1 1 0)CaF₂ stack structure exhibited about 70% transparency with an adsorption edge of approximately 330 nm.     

Characterization of zinc-modified lithium tantalate thin films fabricated by chemical solution deposition method

Zinc-substituted lithium tantalate thin films were fabricated for improving the electrical resistivity by compensating the valence of lattice defects in LiTaO₃ crystal. The films with the chemical composition of (Li_1.00-x Zn _x )TaO₃ were fabricated on (111)Pt/TiO₂/SiO₂/(100)Si substrate by a chemical solution deposition technique using metal-organic precursors. Dense films consisting of a ilumenite-type crystalline phase were deposited by spin coating on the substrates, followed by heat-treatment at 650°C for 5 min in air. The leakage current density of the LiTaO₃ film was reduced from approximately 10⁻⁴ to 10⁻⁶ A/cm² by substituting Zn²⁺ ions for Li⁺ ions in the LiTaO₃ films. Polarization–electric field hysteresis loop was improved significantly by partial substitution of Zn²⁺ for Li⁺ ions, which is based on the enhancement of electrical resistivity.     

Superdomain structure and high conductivity at the vertices in the (111)-oriented epitaxial tetragonal Pb(Zr,Ti)O3 thin film

Recently, in ferroelectric materials, there have been many experimental efforts to find out more intriguing topological objects and their functionalities, such as conduction property. Here we investigated ferroelectric domain structures and related topological defects in the (111)-oriented epitaxial tetragonal PbZr_0.35Ti_0.65O₃ thin film. Systematic piezoresponse force microscopy measurements revealed that the field-induced polarization switching can form thermodynamically stable superdomain structures composed of nano-sized stripe subdomains. Within such superdomain structures, we observed the exotic equilateral triangular in-plane flux-closure domains composed of three stripe domain bundles with 120/120/120 degrees of separation. The conductive-atomic force microscopy measurements under vacuum showed that some vertices have significantly higher conductivity compared to other surrounding regions. This work highlights electric field-driven polarization switching and unique crystallographic symmetry (here, three-fold rotational symmetry) can generate exotic ferroelectric domain structures and functional topological defects, such as conductive vertices.     

Total synthesis of (-)-13-oxyingenol and its natural derivative

Ring functionalization: the total synthesis of a natural derivative of (-)-13-oxyingenol, a potent anti-HIV diterpenoid, is reported. The key steps in this synthesis include a ring-closing olefin metathesis and a Mislow-Evans-type [2,3]-sigmatropic rearrangement. This synthesis provides access to (-)-13-oxyingenol and its natural derivative in 21 steps from a synthetic intermediate previously prepared by Kigoshi and co-workers.