Sanae Ikeda

Utilization of an osmium complex as a sequence recognizing material for DNA-immobilized electrochemical sensor

Abstract A novel immobilized DNA electrode based on a porous carbon electrode was prepared to study interactions between DNA and chemical compounds. The characteristics of this electrode were evaluated by electrochemical methods, and then the interaction between DNA and an osmium complex was studied. On this electrode (electrode surface; 0.66–2.37 cm2), DNA was immobilized at 0.26 × 10−4 − 1.23 × 10−4 mol cm−2. Hybridization of DNA was observed with a relative standard deviation of 11% (n = 4). The tris(bipyridyl)osmium(II/III) ion (osmium complex) was found to interact to major or minor grooves. Using this osmium complex, a DNA sequence could be recognized with more than 12 mer of the same sequence.

Glucose sensor based on titanium dioxide electrode modified with potassium hexacyanoferrate(III)

Abstract A potassium hexacyanoferrate(III) modified titanium dioxide electrode with immobilized glucose oxidase (GOD) was developed for measuring glucose. With this electrode, glucose concentration (1×10 −5 to 1×10 −3 M) could be determined accurately in the presence of ascorbic acid or uric acid. Glucose in human serum was determined after diluting the serum 10-fold with phosphate buffer of pH 5.5. The glucose concentrations of 70.5–72.7 mg dl −1 were determined in good agreement with those usually found in human serum.

Potentiometric argentimetric method for the successive titration of sulphide and dissolved sulphur in polysulphide solutions.

Sulphide sulphur and dissolved sulphur in a polysulphide solution can be successively determined with satisfactory accuracy and reproducibility by potentiometric argentimetry in which a sulphide-selective indicator electrode is used. Before the titration, polysulphide ions need to be converted by an excess of potassium cyanide into thiocyanate and sulphide ions. The excess of cyanide ions is masked with formaldehyde and sulphuric acid, then the solution is made alkaline with ammonia and titrated with silver nitrate till the first end-point is reached (sulphide sulphur). After the acidification of the solution with sulphuric acid, the titration is continued till the second end-point is attained (dissolved sulphur).

PREPARATION AND PROPERTIES OF A MICRO ENZYME SENSOR FOR CREATINE

Abstract A micro enzyme sensor using creatine amidinohydrolase (EC 3. 5. 3. 3) and sarcosine oxidase (EC 1. 5. 3. 1) was developed for measuring creatine. The sensor consisted of platinum and silver wires fixed in a glass tubing with epoxy resin adhesive, and creatine amidinohydrolase and sarcosine oxidase immobilized on their tip by cross-linking method. The calibration curve for measurement of creatine, the effects of pH, temperature, the amount of flavin adenine dinucleotide and compounds on the sensitivity, and the life-time of the sensor were examined. Under optimal conditions, the response of the sensor was linear in the concontration range of 10 μ M ∼ 0.65 mM creatine.

Interaction between immobilized DNA and tris(bpy)osmium(II/III) complex

Abstract The interaction between a tris(bipyridyl)osmium (II/III) ion (osmium complex) and immobilized DNA was studied. The amount of immobilized DNA on the prepared carbon paste electrode (surface area; 0.66–2.37×10−2 cm2) was 0.26–2.78×10−4 mol cm−2. Compared with the bare porous electrode (584 mV), the equilibrium potential of osmium complex with the immobilized single strand DNA electrode shifted to the higher side (650 mV). On the other hand, the equilibrium potential of one with the immobilized double strand DNA (dsDNA) electrode shifted to the lower side (542 mV). These results suggest that the osmium complex interacted specifically with dsDNA. The amount of the osmium complex on immobilized dsDNA electrodes was determined and it gave a good linear plot in the concentration range of 0.5 to 4 mM.

Detection of DNA segment utilizing an immobilized DNA electrode and an osmium complex

Abstract The interactions of an osmium complex with immobilized dsDNA and ssDNA electrodes were studied by linear sweep voltammetry. The appearance of an oxidation peak of the complex indicated that the osmium complex specifically interacted with dsDNA. The osmium complex was concluded to interact electrostatically with phosphate groups, and nonelectrostatically with base pairs and/or the sugar backbone. Recognition of DNA sequences by the osmium complex was examined. The immobilized ssDNA electrode was hybridized with probes, and then the charge of DNA hybrids were measured in phosphate buffer (pH 7.0). After interaction of this electrode with the osmium complex, the charge of the complex was measured in phosphate buffer (pH 7.0). Results showed that complementary probes of more than 12 mers were recognized by the osmium complex, and so that the osmium complex binds to major or minor grooves of the DNA helix.

Studies on analytical methods by amperometric titration using a rotating platinum electrode: Part 47. Successive Determination of L-Cysteine and L-Cystine by Amperometric Titration

Abstract The successive determination of {spl}-cysteine and {spl}-cystine (2–5 μmol of each) in mixtures is achieved by amperometric titration with standard potassium iodate solution using a rotating platinum wire electrode at + 0.6 V vs. SCE. {spl}-Cysteine is titrated in acidic bromide-containing solution; sodium chloride (15 g) is then added and the titration is continued to determine L-cystine.

Rapid Method for the Micro-Determination of Hydrazine by Amperometric Titration With Potassium Iodate

Abstract An amperometric method, with potassium iodate as the titrant, for the rapid and precise determination of micro amounts of hydrazine salts is described. Hydrazine dihydrochloride, hydrazine sulfate and hydrazine hydrate could be quantitatively analyzed at the concentration range of 4 × 10−7 -4×10−3 M in the presence of 5 M hydrochloric acid. Hydrazine salts, 2×10−4 -4×10−3 M, were titrated in 5 minutes with a relative error and a relative standard deviation of 0.1%. It was also found that hydrazine dihydrochloride can be precisely determined, without any interference, even in the presence of hydroxylamine which is ten times as much as the former. The suitable applied potential between the rotating platinum indicator microelectrode and the silver plate-silver chloride reference electrode was + 0.7V.

Nonsuppressed Ion Chromatography of the Mixture of Urea and Alkali Metal Ions Utilizing the Enzyme Reaction

Abstract Non-suppressed ion chromatography with an immobilized enzyme reactor was developed for the simultaneous determination of urea and alkali metal ions. The enzyme reactor was prepared by immo...

Special Articles on Global and Regional Environment and Chemistry. Some lon Concentrations in Rver Water of the Yoshinogawa and their Estimation from Electric Comductivity.

吉野川の水質調査を行い,電気伝導率と溶存イオン種濃度との関係を明らかにし,電気伝導率より主な溶存イオン種を推定する方法を確立した。吉野用の水質は上流から下流に向かってほぼ比例的に溶存イオン種濃度が増加し,各イオン種濃度は下流で2倍以上に達していた。塩化物イオン,硝酸イオン,硫酸イオン,ナトリウムイオン,カリウムイオン,カルシウムイオンおよびマグネシウムイオンの濃度と電気伝導率には高い相関関係(栢関係数0.975以上)が認められた。それらの関係から求めた各イオン種濃度の推定値は生物活動の影響を受けやすい硝酸イオンを除いて,2年後に本流と支流の水質に適用してもイオンクロマトグラフィーの分析値とほぼ一致した。この推定方法は吉野川水系の水質分析結果の評価や溶存イオン種濃度の異常変動の判断などに役立ち,水域の環境管理などに利用できるものと考えられる。