A surface plasmon resonance immunosensor for detecting a dioxin precursor using a gold binding polypeptide

A surface plasmon resonance (SPR) based biosensor was developed for monitoring 2,4-dichlorophenol, a known dioxin precursor, using an indirect competitive immunoassay. The SPR sensor was fabricated by immobilizing a gold-thin layer on the surface of an SPR sensor chip with an anti-(2,4-dichlorophenol) antibody using a gold binding polypeptide (GBP) and protein G. The SPR response based on the antigen-antibody reaction in a flow system was measured by injecting a 2,4-dichlorophenol sample solution into the flow system in which the SPR sensor was located. In a direct immunoassay system using the modified sensor chip, no significant SPR angle shift less than 0.001° was observed when a 25 ppm of 2,4-dichlorophenol solution was injected. In order to improve the sensitivity of the SPR sensor, an indirect competitive immunoassay method was used in conjunction with the SPR sensor system using 2,4-dichlorophenol conjugated with bovine serum albumin (BSA). In the competitive assay, a 350 ppm 2,4-dichlorophenol-BSA conjugate solution containing 2,4-dichlorophenol at various concentrations (10-250 ppb) were injected into the SPR sensor system. The sensitivity of this indirect immunoassay was found to be extremely sensitive, compared to the direct one, and a detection limit of 20 ppb was estimated. Verification that the use of GBP for immobilizing the antibody on the sensor chip enhanced the sensitivity to 2,4-dichlorophenol was obtained by comparing the procedure with another modification, in which BSA was used instead of GBP for immobilizing the antibody on the sensor chip. The affinity constant of 2,4-dichlorophenol and its conjugate to the antibody were estimated form the SPR response.     

Topochemical 3D polymerization of C60 under high pressure at elevated temperatures

Fullerene C60 monomer crystals were compressed to a face-centered cubic (fcc) phase with a lattice parameter of a = 11.93(5) A and a micro-Vickers hardness of 4500 kg/mm2 using high-pressure and high-temperature conditions of 15 GPa at 500-600 degrees C. The hardness is compatible with that of cubic boron nitride (c-BN), suggesting the formation of a 3D C60 polymer. The single-crystal X-ray structural analysis revealed that each C60 molecule in the polymer was linked to the 12 nearest neighbors by [2+2] cycloaddition between the common pentagon-hexagon (56) edges. However, ab initio geometry optimization and molecular dynamics calculations suggested that the 3D polymer should have a rhombohedral structure with the space group of R containing [3+3] cycloaddition between the pentagons of C60 molecules within the plane perpendicular to the 3-fold axis. The higher apparent symmetry of fcc was observed as an averaged structure of different orientations of the rhombohedral structure. The R structure can be derived by only a slight rotation of each C60 unit in the (111) plane of the fcc structure. The band-structure calculation suggested that the 3D polymer (R) was a semiconductor; the activation energy for the electrical conductivity was experimentally determined to be 0.25 eV at 550 K.     

Enzyme‐catalyzed polymerization of L‐aspartate

Diethyl L ‐aspartate was polymerized by proteinase at a temperature between 4 and 50°C to yield poly(ethyl α,β‐L ‐aspartate). Bulk polymerization of diethyl L ‐aspartate, especially at temperatures between 40 and 50°C, and preferably using alkalophilic proteinase with the addition of a small amount of water gave poly(ethyl L ‐aspartate) as a white powder with a molecular weight of up to 3 600 and having about 88% α‐linkages.     

Synthesis and property of novel amino acid‐based polymers by self‐polyaddition of monomers containing both oxetanyl and carboxyl groups

A new synthetic strategy for polymers containing amino acids in the main chain was developed. Monomers N‐oxetanylalanine (N‐Oxe‐Ala‐COOH), N‐oxetanylglutamic acid (N‐Oxe‐Glu‐COOH), and N‐oxetanyllysine (N‐Oxe‐Lys‐COOH) containing both oxetanyl and carboxyl groups were synthesized, and self‐polyaddition and self‐copolyaddition of these monomers afforded the corresponding polymers containing amino acids in the main chain [poly(_OxAla), poly(_OxLys), poly(_OxGlu), poly(_OxAla‐co‐_OxGlu), poly(_OxGlu‐co‐_OxLys), and poly(_OxAla‐co‐_OxLys)] with molecular weight in the range of 920–6620, in satisfactory yields. The physical properties, such as solubility, glass transition temperature, and thermal stability, were consistent with the amount of carboxyl groups at the chain ends. Biodegradability of the polymers was examined by the biochemical oxygen demand method; the decomposition ratios of poly(_OxAla) and poly(_OxAla‐co‐_OxGlu) were about 60%, whereas that of poly(_OxGlu) was nearly 100% after 28 days. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Inheritance and alteration of genome methylation in F1 hybrid rice

We analyzed the inheritance of DNA methylation in the first filial generation(F1) hybrid of Oryza sativa L. ("Nipponbare"x"Kasalath") by restriction landmark genome scanning (RLGS). Most parental RLGS spots were found in the F1, but eight spots (4%) showed abnormal inheritance: seven of the eight spots were missing in the F1, and one was newly detected in the F1. Here we show demethylation at restriction enzyme sites in the F1. We also found a candidate site of stable heterozygous methylation in the genome. These results show the applicability of the RLGS method for analysis of the inheritance and alteration of methylation in F1 hybrid plants.     

Spectrophotometric determination of carp vitellogenin using a sequential injection analysis technique equipped with a jet ring cell

A sequential injection analysis (SIA) technique, in which antibody-immobilized microbeads were transferred to a jet ring (JR) cell, was used in determination of carp vitellogenin (Vg). The determination is based on a sandwich immunoassay in which two types of reactions between anti carp Vg antibodies and carp Vg are used. Namely, the antibody for the first reaction step was immobilized on microbeads (Sephadex beads), and an antibody labeled with a horseradish peroxidase (HRP) was used in the second step of the reaction. A mixed solution of hydrogen peroxide and o-phenylenediamine (OPD) was used as the source of the chromophore in the reaction. The microbeads-immobilized antibody, Vg analyte, HRP-labeled anitbody and the color developing solution were introduced automatically into the JR cell of the SIA system in a programmed sequence, and the absorbance of the oxidized OPD product was used to determine the amount of Vg present. The optimal incubation times for the immuno-raction for the first and the second steps were determined at 120 and 60 min, respectively, taking into account the sensitivity to the Vg determination. Under these conditions, a good linear correlation was obtained between Vg concentration and the absorbance of the oxidized OPD. The lower detection limit for the determination of Vg was about 5 ng ml⁻¹ in this system. The method developed here represents a simple, accurate method for the determination method of Vg.