Sumiko Suzuki

Stability of microcystins from cyanobacteria—II. Effect of UV light on decomposition and isomerization

Microcystins are very potent hepatotoxins and strong liver tumor promoters produced by cyanobacteria, and their occurrence has been reported all over the world. They could threaten human health when toxic Microcystis occurs in water supply reservoirs. In this study, we examined the stability of microcystins during photolysis with UV light. The toxins were easily decomposed by UV light at wavelengths around the absorption maxima of the toxins and the decomposition depended on the intensity of the light. The half-life of microcystin LR by 147 microW/cm2 UV irradiation was 10 min, and the toxin was completely decomposed by 2550 microW/cm2 UV after 10 min. When the toxins were irradiated with weaker UV light, isomerization was also observed by a different mechanism from that during photolysis by sunlight and pigment, and several products including three geometrical isomers of the conjugated diene of Adda were detected. Microcystin RR showed almost the same behavior as that of microcystin LR under the same conditions. Since no noxious products were formed in the present study, a water treatment including UV irradiation is very possible for removing microcystins from raw water.

Determination of synthetic food dyes by capillary electrophoresis

A method for the determination of synthetic tar dyes used as food additives using capillary electrophoresis with photodiode-array detection was investigated. The dyes Erythrosine (R-3), Phloxine (R-104), Rose Bengal (R-105), Acid Red (R-106), Amaranth (R-2), New Coccine (R-102) and Allura Red AC (R-40) were separated on a capillary column (50 cm x 75 microns I.D.) and identified from the absorbance spectra of each peak. The electrophoresis buffer used was a mixture of 25 mM sodium phosphate buffer and 25 mM sodium borate buffer (1:1) (pH 8.0) containing 10 mM sodium dodecyl sulfate (SDS). Substitution of beta-cyclodextrin for SDS in the electrolyte buffer was effective for the separation of R-2 and R-102. This modified method could be employed as an additional assay method for these two dyes.

Determination of organic acids in urine by capillary zone electrophoresis

The simultaneous measurement of organic acids was studied using capillary electrophoresis with direct measurement of UV absorption at 185 nm. The organic acids studied were oxalic, formic, malonic, fumaric, succinic, alpha-ketoglutaric, citric, acetic, pyruvic, lactic, isovaleric and hippuric acid. They were separated in a fused-silica capillary (100 cm x 75 microm I.D.) filled with 50 mM borax buffer (pH 10.0) containing cationic surfactant as the electroosmotic flow modifier. The method was successfully applied to the determination of organic acids in urine in comparison with an organic acid analyser.

A clean-up method for analysis of trace amounts of microcystins in lake water.

A clean-up method using high performance liquid chromatography (HPLC) and liquid chromatography/mass spectrometry (LC/MS) was developed to pursue trace amounts of microcystins in lake water. The method consisted of the combined usage of octadecyl silanized (ODS) silica gel and silica gel cartridges. In the first clean-up process, the retention behavior of microcystin RR on ODS silica gel cartridge was carefully observed together with microcystin LR, and 10% water-methanol was chosen as the best solvent system to elute microcystins from the ODS silica gel cartridge. Because many impurities still remained in the desired fraction from the raw water even after the clean-up with ODS silica gel, an additional clean-up process was developed using various cartridges. As a result of extensive experiments, the second clean-up process using silica gel cartridge was established, and the impurities were effectively eliminated. The present method including a tandem cartridge system allowed a precise analysis of microcystins in water samples from three different lakes at a 0.02 ppb level.

Inhibitory effects of pectic substances on activated hyaluronidase and histamine release from mast cells

In this paper, we report the effect of pectic substances and D-galacturonic acid, the main constituent of pectic substances, on activated hyaluronidase and histamine release from mast cells. Although D-galacturonic acid itself showed no inhibition, IC50 values of hyaluronidase inhibition were correlated with the D-galacturonic-acid content of pectic substances. It was thought that the polymerization of D-galacturonic acid was necessary for inhibition of activated hyaluronidase. This type of inhibition was suggested to be non-competitive by the Lineweaver-Burk plot. Furthermore, pectic substances, including those purified from Gymnema sylvestre, inhibited histamine release from isolated rat peritoneal mast cells, which had been induced by the antigen. These results suggest that pectic substances may have anti-allergic activities.

Analysis of creatinine, vanilmandelic acid, homovanillic acid and uric acid in urine by micellar electrokinetic chromatography

A simultaneous determination of vanilmandelic acid, homovanillic acid, creatinine and uric acid using capillary electrophoresis was investigated. The optimum conditions of buffer concentration, pH and surfactant concentration were studied, and high resolution was obtained using a 30 mM phosphate buffer (pH 7.0) containing 150 mM sodium dodecyl sulfate. The detection was by UV absorbance at 245 nm and the column was a fused-silica capillary of 67 cm x 75 microm I.D.. The determination of these metabolites in human urine was completed within 15 min without any interferences.

Flow analysis of UV-irradiated chemicals by chemiluminescence and electron spin resonance spectroscopy

Abstract A novel method for detecting changes in chemicals, especially radical formation after ultraviolet (UV) irradiation, was developed using imipramine as a marker of light-sensitive materials. The system consisted of a pump, an injection port for the sample, an on-line UV irradiation device and detectors for chemiluminescence and electron spin resonance (ESR). Most chemicals that were chemiluminescence positive after UV irradiation in this flow system were found to show spectra of free radicals by ESR spectroscopy. These results suggested that the proposed on-line system may be useful for the rapid and simple determination of the stability and light-induced degradation of chemicals.

Chemiluminescence detection of organotin compounds with bis(2,4,6-trichlorophenyl) oxalate by flow-injection analysis

Abstract The chemiluminescence (CL) reaction of bis(2,4,6-trichlorophenyl) oxalate with hydrogen peroxide was applied to the detection of fluorescent organotin-quinoline complexes using a flow-injection system. Four organotin compounds, i.e., di- n -butylin dichloride (DBTC), diphenyltin dichloride (DPTC), tri- n -butylin chloride (TBTC) and triphenyltin chloride (TPTC), were examined in conjunction with 2-methyl-8-hydroxyquinoline. Factors affecting the CL intensity such as solvents, reagent concentrations, pH and flow-rate were studied. The detection limits for DBTC, DPTC, TBTC and TPTC were 0.5 μM (3 ng), 1.25 μM (8.6 ng), 25 μM (162.7 ng) and 100 μM (770.9 ng), respectively, with a signal-to-noise ratio of 3.

Studies on endogenous phosphorylation of chicken erythrocyte membranes. Calcium-dependent phosphorylation of specific proteins

In this work, endogenous phosphorylation of chicken erythrocyte membranes was investigated. The membrane proteins were rapidly phosphorylated endogenously (half maximum time was 30 s) in the presence of millimolar concentration of Mg2+ under physiological conditions. As an exogenous substrate, protamine was phosphorylated most rapidly of those tested, and histone, casein and bovine serum albumin were rather poor substrates. Cyclic nucleotides had no effect on the endogenous membrane phosphorylation. EGTA inhibited the phosphorylation of a membrane protein having an approximate molecular weight of 43000, and this inhibition was reversed by the addition of a stoichiometric amount of Ca2+. Furthermore, trifluoperazine, an inhibitor of calmodulin, was found to have the same effect as that of EGTA. The phosphorylated 43 kDa protein could be extracted from the membranes under high salt conditions, and was precipitated specifically with anti-actin antibody. These results suggest that the phosphorylation of a peripheral membrane protein (which has an approximate molecular weight of 43000) of chicken erythrocytes by membranous protein kinase(s) depends on Ca2+ and possibly on calmodulin.

Analytical Chemistry in Medical Science and Technology. Estimation of modified polymer surface by the activation of differentiated HL-60 cells.

医用材料は,滅菌処理並びに表面の改質がなされているが,これらの材料が細胞に与える影響を検討した.すなわち,γ-線及びアルゴン(Ar)プラズマをポリスチレンに照射し,接触角により表面の物理化学的変化を測定するとともに,好中球様HL-60細胞が材料に接触した際に産生される活性酸素を,ルミノール依存性化学発光により測定した.ポリスチレンにγ-線あるいはArプラズマ照射を施すことで,接触角は減少し,表面の親水性化が確認された。又,ポリスチレンに接触した細胞から産生される活性酸素産生量に,照射による影響が認められ,好中球様HL-60細胞を用いた生物学的方法により照射したポリスチレン表面の微小な変化をとらえることができた.