Mitsue Kobayashi

A theoretical study on the zone mobility-pH curve in paper electrophoresis of low molecular weight compounds with a dissociable proton and its application to phosphorus compounds

Abstract It was found that the zone mobility of a compound with dissociable proton plotted against the pH value of the background solution is approximately expressed by a hyperbolic tangent function. By the use of this relation, we can easily draw the zone mobility-pH value of the background solution is approximately expressed by a hyperbolic tangent function. By the use of this relation, we can easily draw the zone mobility-pH curve of migrating species and estimate the consecutive dissociation constants. The relationships between the mobility and the molecular weight or the hydrated ionic radius were also discussed. Jokls equation is only applicable to the first dissociation of a migrating substance and the deviation increases with increasing charge number because of the hydration increment. After considering the hydration ratio, we proposed a modification of the equation. The observed relative zone mobility-pH curves of phosphorus compounds such as phosphorus oxyacids, phenylphosphorus compounds and phosphoric esters of hexoses or inosines were in fair agreement with the calculated ones. The equation proposed is useful in practice for the estimation of the dissociation constant and/or molecular weight of an unknown sample.

Electrophoretic behaviour and infrared spectra of dihydroxyboryl compounds in aqueous di- and tricarboxylic acids: Paper electrophoresis as a tool for determining the chemical states of a substance in solution

Abstract p -Dihydroxyborylphenylalanine behaved as an anion in aqueous 0.1 mol dm −3 oxalic acid and 0.1 mol dm −3 citric acid in paper electrophoresis, but as a cation in aqueous 0.1 mol dm −3 fumaric, malic, tartaric, succinic, maleic and malonic acid. A similar electrophoretic behaviour was observed for boric acid. These results indicate that dihydroxyboryl compounds form complexes with oxalic and citric acid. The complex formation was confirmed by the infrared spectra of boric acid in the two aqueous carboxylic acids. The spectral behaviour was fully consistent with the migration behaviour in paper electrophoresis. It was confirmed that paper electrophoresis is a useful technique for determining the chemical states of a compound in solution.

Studies of the electrophoretic behaviour of p-dihydroxyborylphenylalanine and related compounds by the three-spot method

Abstract The effects of capillary action and electro-osmotic flow on the electrophoretic migration of p-dihydroxyborylphenylalanine (BPA) and related compounds were determined by spotting a sample solution at three different positions on the support. The zone electrophoretic behaviour of phenylalanine analogues was studied in support solutions of various pH values. A specific interaction between BPA and oxalate ions was found, which will be useful in the isolation of BPA from phenylalanine analogues.

Partial Deuteration and Blood-Brain Barrier (BBB) Permeability

Boron neutron capture therapy (BNCT) is one method of radio-surgery used for malignant brain tumor. The theory of this method is based on the nuclear reaction that occurs when boron-10 is radiated with and absorbs neutrons. When treating deep-seated brain tumor, partial deuteration of body water is used to improve the penetration of neurons into the tissue. In order to investigate the change in the BBB function under partial deuteration, we measured brain water content and the permeability of protein. Wistar rats were given 99% heavy water (approx. 10% of body weight/day) as drinking water. On the day of the experiment, all animals received 125-I labeled albumin as a tracer of protein. Light water in the control group or heavy water (D2O) in the experimental group was given by drip infusion for 60 min. Heavy water was measured by infrared spectroscopic analysis. Water content was measured by the freeze-dry method. The radioactivity of 125-I was determined with a gamma scintillation counter. Mean values of D2O concentration in the tissue were 17.9-36.5%. Water content increased in the cortex in all animals. The ratio of 125-I in the brain tissue to blood showed significant differences between the control group and animals deuterated to more than 30% of body water. Brain tissue deuterated over 10% showed a mild leakage of water, indicating the early stage of brain edema. Deuteration higher than 30% caused a leakage of protein, which might indicate the leakage of boron compound from the vessels into the normal brain tissue.

Hot Atom Chemistry of Phosphorus Compounds

The recoil reaction of P produced by the 3 P(n, y)P reaction of phosphorus compounds, such as triphenylphosphine, triphenylphosphine oxide, triphenylphosphite, diphenylphosphite, triphenylphosphate, phenylphosphinic acid and white phosphorus, has been investigated in benzene solutions of various concentrations. The P-labeled recoil products produced in irradiated samples were analysed by paper chromatography and paper electrophoresis. In concentrated solutions the composition and the yield of the P-labeled recoil products are strongly affected by the chemical composition of target materials. This dependence becomes less noticeable with decreasing concentration. The curve of the yields of the recoil product plotted against the concentration shows a maximum, the position of which varies from one recoil product to another. However, for a given radioactive product it is almost independent of the choice of the target materials. The influence of benzene, as a moderator and a reagent, on the chemical behavior of P is discussed.

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.

Reactor-irradiation of phenylphosphorus compounds below 20°K

Abstract A series of phenylphosphorus compounds were neutron irradiated below 20°K and 32 P-labelled recoil products were analyzed by both solvent extraction and paper chromatography. The identities and yields of recoil products are compared with those produced by dry ice temperature irradiation and by a reactor temperature irradiation. In triphenylphosphine, triphenylphosphine oxide and triphenylphosphate, considerable differences due to the irradiation temperature have been observed. At 20°K, more than 30% of the 32 P has not completed its chemical reactions and has been trapped as intermediates in the crystals. In phenylphosphinic acid and phenylphosphonic acid, however, the irradiation temperature has only little effect on the nature of the products and their yields. It is concluded that P-C bond formation by phosphorus atoms or radicals with phenyl groups mainly occurs in a hot reaction in the high energy region, while the P-OH bond formation occurs in the thermal region as well as in the hot region.

The Complexation of p-Boronophenylalanine with Alcohols or Carboxylic Acids Studied by Zone Electrophoresis

Recently many researchers have paid their attention to p-boronophenylalanine (p-BPA) as a boron carrier for boron neutron capture therapy. As p-BPA is sparingly soluble in water, the fructose-p-BPA complex has been used in the actual administration of p-BPA. The transportation or accumulation of p-boronophenylalanine in organic tissues or in cells largely depends on the interaction between the dihydroxyboryl moiety and functional groups of biological materials. The complexation of boric acid with alcohols has been studied by many workers from early days and been applied to chemical analysis.1 During studies of the physicochemical nature of p-BPA, we first found the complexation of p-BPA with oxalic acid by the use of paper electrophoresis.2 Since then, we have been studying the interaction between p-BPA or its related compounds and car-boxylic acids using paper electrophoresis.3,4 In this report, we would like to show electrophoretic behavior of p-BPA in alcohol or carboxylic acid supporting solutions. Based on these results, the charge state and chemical stability of the complexes of p-BPA in different pH solutions will be discussed.

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.

Chemical Behavior of Boron-Containing Amino Acids for Neutron Capture Therapy in Aqueous Solutions

Because of poor solubility of p-boronophenylalanine (BPA) in water, BPA-fructose complex has been used at clinical experiments of BNCT1. Complexation is a method of choice to improve the solubility of BPA2. Based on the electrophoretic behavior, we had reported that BPA formed negatively charged complexes with some carboxylic acids such as oxalic acid and citric acid3. Chemical states of BPA in aqueous oxalic acid and in aqueous fructose were investigated mainly by infrared (IR) spectroscopy. The chemical nature of dihydroxyboryl group of p-boronophenylserine (BPS) in the aqueous solutions was examined and compared with that of BPA.