Michiya Kimura

Kinetic analysis of the fluorescence reaction of histamine with orthophthalaldehyde

Histamine reacts with orthophthalaldehyde (OPA) in an alkaline medium to form an unstable fluorescent adduct (Fbase). Acidification of the solution gives a stable adduct (Facid). In order to elucidate the mechanism of this fluorescence reaction, a kinetic study of this reaction was carried out. Although Fbase was believed to be the precursor of Facid, it was shown not to be the precursor of Facid owing to the effects of the reaction time in an alkaline medium and OPA concentration on the yields of Fbase and Facid. The kinetic analysis of the formation and degradation of Fbase revealed the pathway of the fluorescence reaction. On the basis of the results obtained in this study, the mechanism of the fluorescence reaction is proposed.

Scanning magnetoresistance microscopy with a magnetoresistive sensor cantilever

In this work, a cantilever with a magnetoresistive (MR) sensor is fabricated for scanning magnetoresistance microscope, in order to realize the simultaneous imaging of surface topography and stray magnetic field distribution. A constant current flowing through a meander-patterned metal wire produces a defined magnetic field, and the wire is used as a sample to demonstrate the simultaneous imaging and to reveal the field sensitivity of the cantilever. A MR image has been successfully obtained with lateral spatial resolution of a few μm and a field sensitivity (Hmin≈1.7 Oe) at room temperature.

A fluorometric method for the specific determination of serum arginine with 2,3-naphthalenedicarbaldehyde.

A specific and simple fluorometric method for the determination of serum arginine was developed which consists of (1) deproteinization of serum sample with 10% perchloric acid, (2) blocking thiol compounds with N-ethylmaleimide, (3) fluorescence reaction with 2,3-naphthalenedicarbaldehyde in 0.2 M borate buffer, pH 9.3, in the presence of beta-cyclodextrin (25 min at 20 degrees C, excitation wavelength: 462 nm, emission wavelength: 520 nm). Since the fluorescence reaction is highly specific for arginine, the method requires no other separation step. Linearity, recovery, and reproducibility of the method were found to be satisfactory.

Novel stereochemical feature of epoxidation with hydrogen peroxide–tris(acetylacetonato)iron(III) system

trans-Epoxide is obtained as the major product in the reaction of hydrogen peroxide–tris(acetylacetonato) iron(III) system with both cis and trans-olefins such as stilbene, octadecenol, and the methyl ester of unsaturated higher fatty acids.

An enzymatic method for the assay of serum argininosuccinate lyase.

A rapid enzymatic method was developed for the assay of serum argininosuccinate lyase (ASAL: EC 4.3.2.1) which is a useful marker enzyme for diagnosis of parenchymal liver diseases. Fumarate, liberated from argininosuccinate in the lyase-mediated reaction, was converted to pyruvate via L-malate by the actions of fumarase and malic enzyme in the presence of NADP+. The NADPH formed was then oxidized with a diaphorase-resazurin system to give a highly fluorescent resorufin. All the enzymatic reactions proceeded continuously in 0.1 M Tris-HCl buffer (pH 7.5) and allowed direct assay of ASAL in serum by monitoring the increase in the fluorescence intensity due to resorufin. The method is rapid and sensitive; only 50 microliter of serum is required. This method was used to detect increases in the activities in sera from patients with liver diseases.