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Volume 46, Issue 2
Displaying 1-5 of 5 articles from this issue
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Zenko YOSHIDA2000 Volume 46 Issue 2 Pages 83
Published: September 29, 2000
Released on J-STAGE: June 28, 2010
JOURNAL FREE ACCESSDownload PDF (157K) -
Jingyuan CHEN, Koichi AOKI2000 Volume 46 Issue 2 Pages 85-104
Published: September 29, 2000
Released on J-STAGE: March 01, 2011
JOURNAL FREE ACCESSPolynuclear metal complexes of which redox sites are connected with π-conjugated ligands take a number of mixed valence states. They exhibit several redox potentials owing to interaction between redox centers through the π-conjugated bridges. Questions arise about the definition of the interaction, a relation between the number of nuclei and the number of redox potentials, and a relationship between redox potentials and geometry of the complexes. This paper answers these questions thermodynamically as well as quantum mechanically. The interaction energy in this paper is defined as a pair energy between a reduced and an oxidized sites. Even this simplest definition generates complicated redox behaviors because of formation of various isomers when the number of metal centers increases.View full abstractDownload PDF (2688K) -
Hideaki KINOSHITA2000 Volume 46 Issue 2 Pages 105-113
Published: September 29, 2000
Released on J-STAGE: June 28, 2010
JOURNAL FREE ACCESSMany substances in serum are criteria for many diseases. Unfortunately, a determination of clinically important substance is mainly performed by a colorimetric method An electrochemical method has advantages of being free from the influence of turbidity and coloration of a test solution and having a wide dynamic range as compared with a colorimetric method. An electrode or an enzyme-trapped electrode was severed with a dialysis membrane to prevent the adsorption of protein in a test solution to the electrode surface. The steady state current at a fixed potential was measured with the solution being stirred The enzyme activities in serum could be determined by measuring the increase or decrease in current due to hydrogen peroxide (using peroxidase entrapped ferrocene embedded carbon paste electrode, mPOFcCPE), NADH (using plastic formed carbon electrode, mPFCE, and mPOFcCPE in the presence of l-Methoxy-5-methylphenazinium methyl sulfate), thiols (using glassy carbon electrode, mGCE), phenols (using mGCE) and uric acid (using mGCE) with the use of auxiliary enzymes of converting a substrate or product to the above-mentioned electro-active substances when necessary. Electro-active compounds in serum have no influence on this method, since the current due to these compounds remained constant in the course of measurement. In the determination of biochemical substances except enzyme, the current increase after the addition of enzyme or combination of enzymes that converts the object to the electro-active substance was measured In this method, an electro-active substance in serum such as uric acid did not interfere with the determination.View full abstractDownload PDF (1588K) -
Haruki SHIRAISHI, Toshio MATSUDA2000 Volume 46 Issue 2 Pages 115-122
Published: September 29, 2000
Released on J-STAGE: June 28, 2010
JOURNAL FREE ACCESSThe aim of the present paper is to review research efforts in the area of electrochemical DNA analysis. The oxidation, adsorption and determination of DNA at carbon electrodes were described for the first time 10-20 years ago. In recent years, sequence specific biosensors for the detection of DNA sequences have been studied widely. The DNA electrochemical sensor is based on the adsorptive attachment of ss-olygonucleotide probes onto the carbon paste transducer, their hybridization with the complementary sequence targets, binding of the indicator to the hybrid, and chronopotentiometric monitoring of the hybridization process (via the increased indicator peak). This biosensor allowed direct quantification of the target sequence following short (10-30 min) hybridization time. Also ds-DNA modified electrodes can be employed for detecting analytes (hydrazine, quinacrme, etc.) interacting with DNA immobilized layers. While the use of DNA biosensors is at a very early stage, these and similar developments are expected to have a profound effect on DNA analysis.View full abstractDownload PDF (1063K) -
Noriko OKUMURA2000 Volume 46 Issue 2 Pages 123-135
Published: September 29, 2000
Released on J-STAGE: June 28, 2010
JOURNAL FREE ACCESSCharge-transfer (CT) complex formation based on molecular recognition of organic π-dianions has been investigated by electrochemistry and spectroelectrochemistry combined with ab initio MO calculations. p-Quinone dianions (PQ2-) forms the 1:2 hydrogen-bonded complexes with McOH at low concentrations of McOH, and the 1:4 complexes at high concentrations. The hydrogen bonding of PQ2- with McOH is characterized by the geometrical and spectral properties. It is demonstrated that this situation is due to the strong n-σ CT interaction in the hydrogen bonds. The results suggest that the differing functions and properties of biological quinones are conferred by the n-σ CT interaction through hydrogen bonding of the dianions with their protein environment. On the other hand, it has been demonstrated that π-dianions of redox-active organic molecules such as chloranil (CL) and TCNE form the π-π type CT complexes with 4nπ biphenylene (BP). Spectroelectrochemistry evidently gave the intermolecular CT spectra in the CL2--BP and TCNE2--BP systems. The complex formations are due to molecular recognition based on the favorable intermolecular HOMO-LUMO interaction of the dianions with BP, and the geometries of the dianion complexes differ from those of the neutral complexes. This background led to the development of the redox-mediated bistable complex formation systems characterized by the geometrical alteration and the chromatic change. The interconversion of the bistable complex formation in the systems is modulated through redox control of the intermolecular HOMO-LUMO interaction, with trichromic change arising from the neutral complex formation, the anion radical generation, and the dianion complex formation.View full abstractDownload PDF (1777K)
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