Mitsunori Kirihata

Electrophoretic study of the interaction of p-boronophenylserine with carboxylic acids by the three-spot method

The electrophoretic behaviour of p-dihydroxyborylphenylserine (BPS) was studied by spotting a sample solution at three different positions on the support (a pure cellulose paper). Electrophoretic migration of BPS was carried out using organic di- and tricarboxylic acid supporting solutions. A strong interaction between BPS and oxalic or citric acid was observed by paper electrophoresis. This interaction could be applied to isolation of BPS from a mixture of common amino acids. The separation of BPS from p-boronophenylalanine (BPA) could be made in sodium borate solution.

Effects of Sugar Acids on the Functions of Ribulose Bisphosphate Carboxylase/Oxygenase: Differentiation of Two Different Ligand-binding Modes of the Catalytic Sites.

The effects of sugar acids on the kinetics and the protein conformation of ribulose 1,5-bisphosphate carboxylase/oxygenase (RuBisCO) were examined to differentiate the ligand-binding modes of the catalytic sites. D-Glucarate, L-glucarate, and mucate inhibited the carboxylase activity of RuBisCO competitively with respect to ribulose 1,5-bisphosphate. Their inhibition constants were 2.5 to 8.5 mM. The sugar acids induced such a change of the protein conformation of activated RuBisCO as is detected with a hydrophobic fluorescence probe. However, the change was not concerned with hysteresis of the enzyme. The sugar acids bound to· the catalytic sites retarded the release of activator CO2 from the sites in the absence of CO2. These characteristics of the sugar acids were quite similar to those of 6-phosphogluconate, but not of fructose bisphosphate or 3-phosphoglycerate. It is proposed that sugar phosphates that bind to the catalytic sites of RuBisCO could be divided into two groups on the basis of the modes of the binding to the sites.

Development and Elucidation of a Novel Fluorescent Boron-Sensor for the Analysis of Boronic Acid-Containing Compounds

Novel boron-containing drugs have recently been suggested as a new class of pharmaceuticals. However, the majority of current boron-detection techniques require expensive facilities and/or tedious pretreatment methods. Thus, to develop a novel and convenient detection method for boron-based pharmaceuticals, imine-type boron-chelating-ligands were previously synthesized for use in a fluorescent sensor for boronic acid containing compounds. However, the fluorescence quantum yield of the imine-type sensor was particularly low, and the sensor was easily decomposed in aqueous media. Thus, in this paper, we report the development of a novel, convenient, and stable fluorescent boron-sensor based on O- and N-chelation (i.e., 2-(pyridine-2yl)phenol), and a corresponding method for the quantitative and qualitative detection of boronic acid-containing compounds using this commercially available sensor is presented.

Study of the Interaction of P-Boronophenylalanine and Its Analogs with Various Carboxylic Acids by Using Zone Electrophoresis

The chemical nature of a boron carrier in an aqueous solution plays an importnat role in its metabolism. The charge state and interaction of a compound can be determined by zone electrophoresis. We investigated the chemical state of p-boronophenylalanine (BPA), its related amino acids and p-boronophenylserine (BPS) using a “three-spot method” which was developed by Kitaoka1.