Signal amplification by substrate recycling on polyaniline/lactate oxidase/lactate dehydrogenase bienzyme electrodes

The bienzyme electrodes were fabricated by coimmobilization of lactate oxidase (LOD) and lactate dehydrogenase (LDH) onto electrochemically prepared polyaniline (PANI) films. These PANI/LOD/LDH bienzyme electrodes were shown to provide signal amplification by substrate recycling, making it possible to detect l-lactate at lower concentrations (0.1-1 mM). The PANI/LOD/LDH bienzyme electrodes were found to be stable for about 21 d at 4–10°C.     

Determination of lactate and lactic dehydrogenase by biamperometric monitoring of hexacyanoferrate(II) in a flowing stream

Summary Open tubular carbon electrodes were used to monitor the biamperometric current of hexacyanoferrate(II) ion produced by the LDH catalyzed reaction between hexacyanoferrate(III) ion and lactate, and that produced from the diaphorase catalyzed reaction between hexacyanoferrate(III) ion and NADH, product from the LDH catalyzed reaction between lactate and NAD. Reagents and samples were mixed in a flow stream. Reaction takes place between the mixing point and the electrodes, and measurements are taken after a constant time interval. Lactate and LDH standards in serum control solutions were measured using the NAD dependent reaction.

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Bestimmung von Lactat und Lactatdehydrogenase durch biamperometrische Messung von Hexacyanoferrat(II) im Durchfluß

Zusammenfassung Kohlenstoff-Röhrenelektroden wurden zur Messung des biamperometrischen Stromes des Hexacyanoferrat(II)-ions eingesetzt, das aus der LDH-katalysierten Reaktion zwischen Hexacyanoferrat(III) und Lactat bzw. der Diaphorase-katalysierten Reaktion zwischen Hexacyanoferrat(III) und NADH (Produkt der LDH-katalysierten Reaktion zwischen Lactat und NAD) stammte. Die Reagentien wurden mit den Proben im Durchfluß vermischt. Die Reaktion fand zwischen der Mischungsstelle und den Elektroden statt und die Messungen wurden nach einem Bestimmten Zeitintervall durchgeführt. Mit Hilfe der NAD-abhängigen Reaktion wurden Lactat- und LDH-Standards in Serumkontrollösungen bestimmt.

     

Biobased myo-inositol as nucleator and stabilizer for poly(lactic acid)

myo-Inositol made from a biomass feedstock was used as an additive for poly (l-lactic acid) (PLLA) which was also made from biomass feedstock. The crystallization and stabilization of PLLA by the addition of myo-inositol were evaluated by the melt injection molding process. While the isothermal crystallization of PLLA at 100 °C had finished over 14 min after melting, that of PLLA with 5 wt% myo-inositol finished within 2 min. The crystal growth of PLLA started when the myo-Inositol crystal was added, and the crystallization was promoted. Furthermore, the molecular weight of PLLA with myo-inositol did not decrease during the melt-mixed at 200 °C, different from that of PLLA without the myo-inositol. myo-Inositol prevented the degradation of PLLA during the thermal melting process. The biomass carbon ratio measured by the accelerator mass spectroscopy method showed that the PLLA with 5 wt% myo-inositol was a fully biobased material. It was demonstrated that myo-inositol was a multi-functional biobased additive for the modification of PLLA without decreasing its mechanical properties.     

Achievement of ring inversion of myo-inositol derivatives due to silyloxy/silyloxy repulsion enhanced by the trans-substituents on both sides

The introduction of quite bulky trialkyl or diarylalkylsilyl groups into vicinal trans-hydroxy groups induced a conformational flip of certain multifunctionalized cyclohexane rings from the usual chair form possessing more equatorial substituents (equatorial-rich chair form) into another chair-form that has more axial substituents (axial-rich chair form). This realization was experimentally revealed by the conformational study of the synthetic myo-inositol derivatives possessing two tert-butyldimethylsilyl (TBS), two triisopropylsilyl (TIPS), or two tert-butyldiphenylsilyl (TBDPS) groups on an adjacent trans-diol. Among them, the cyclohexane rings of the 4,5-bis-O-TIPS-myo-inositol, 4,5-bis-O-TBDPS-myo-inositol, and 1,2,3,6-tetra-O-benzyl-4,5-bis-O-TBDPS-myo-inositol were in the axial-rich chair form. Comparison of the ring conformations also revealed that the order of the repulsion was OTBDPS/OTBDPS>OTIPS/OTIPS>OTBS/OTBS, and the silyloxy/silyloxy repulsion was enhanced when the two silyloxy groups were placed in the center of the contiguous four equatorial substituents.     

Regioselective O-acylation of myo-inositol 1,3,5-orthoesters: dependence of regioselectivity on the stoichiometry of the base

A metal mediated unusual 1-3 acyl migration from C4-O to C2-OH of myo-inositol 1,3,5-orthoformate was observed during the alkylation of racemic 4-O-benzoyl-myo-inositol 1,3,5-orthoformate. This has been exploited for the selective esterification of either the C4(6)-OH or the C2-OH of myo-inositol by varying the amount of the base used. While the use of 1 equiv of the base (sodium hydride or potassium tert-butoxide) for the acylation of myo-inositol orthoesters gives the corresponding C4-ester exclusively, the use of two or more equivalents of base for the same reaction gives the C2-ester exclusively. The relatively higher stability of the alkoxide of racemic 2-O-acyl-myo-inositol 1,3,5-orthoester as compared to the alkoxide of 4-O-acyl-myo-inositol 1,3,5-orthoester is suggested to be responsible for the observed isomerization.     

Die γ-Bestrahlung von Phytinsäure in wäßriger Lösung

Cleavage products observed to arise as a result of irradiation at a dose of 30 Mrad weremyo-inositol tetraphosphate,myo-inositol pentaphosphate andmyo-inositol isopentaphosphate.     

Die Überführung vonmyo-Inosit in chinoide Substanzen inPseudomonas beijerinckii, 1. Mitt.: Über einemyo-Inosit-Dehydrogenase ausPseudomonas beijerinckii

Zusammenfassung Ein konstitutives Enzym mit der Spezifität einermyo-Inosit-Dehydrogenase (myo-Inosit: NAD-Oxydoreductase, ES 1.1.1.18) wurde ausPseudomonas beijerinckii isoliert, etwa 550fach angereichert und in seinen Eigenschaften charakterisiert.

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Transformation of myo-inositol to quinoid substances in pseudomonas beijerinckii, I: On a myo-inositol dehydrogenase of pseudomonas beijerinckii

A constitutive enzyme showing the specificity of amyo-inositol dehydrogenase (myo-inositol: NAD oxidoreductase, EC 1.1.1.18) has been isolated fromPseudomonas beijerinckii. It was concentrated to 550fold activity; its properties were determined.

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Mit 3 Abbildungen     

Inositol derived crown ethers: effect of auxiliary protecting groups and the relative orientation of crown ether oxygen atoms on their metal ion binding ability

The binding constants of crown ethers prepared from tetra-O-substituted myo- and scyllo-inositol derivatives and 2-O-substituted myo- and scyllo-inositol-1,3,5-orthoformates, with metal picrates show that the O-substituents and the relative orientation of the crown ether oxygen atoms contribute significantly to the binding of crown ethers with metal ions. In particular, the binding efficiency of myo-inositol derived crown ethers to silver and potassium ions could be enhanced by introducing benzyl ethers in the inositol ring. Hence binding efficacy and selectivity of metal ions to inositol derived crown ethers can be tuned by varying substituents on the myo-inositol ring and/or the relative orientation of crown ether oxygen atoms.     

NMR and X-Ray Diffraction Study of Some Inositol Derivatives 1

Abstract

We have determined the preferred conformers in solution by a detailed NMR analysis using COSY and HETCOR experiments of three inositol isomers: myo (1), scyllo (2) and epi (3) plus sixteen derivatives of myo-inositol: 1,2,3,4,5,6-hexa-O-acetyl-myo-inositol (4), 1,2,-O-isopropylidene-myo-inositol (5), 1,2:4,5-di-O-isopropylidene-myo-inositol (6), 3,4,5,6-tetra-O-acetyl-1,2-O-isopropylidene-myo-inositol (7), 3,4,5,6-tetra-O-acetyl-myo-inositol (8), 1,2-O-isopropylidene-3,6-di-O-tosyl-myo-inositol (9), 1,2-O-isopropylidene-3,4,6-tri-O-tosyl-myo-inositol (10), 1,2:4,5-di-O-isopropylidene-3-O-tosyl-myo-inositol (11), 3,6-di-O-benzyl, 1,2:4,5-di-O-isopropylidene-myo-inositol (12), 3,6-di-O-benzyl-1,2-O-isopropylidene-myo-inositol (13), 3,6-di-O-benzyl-myo-inositol (14), 1,2-O-cyclohexylidene-myo-inositol (15), 1,2:4,5-di-O-cyclohexylidene-myo-inositol (16), 1,2:5,6-di-O-cyclohexylidene-myo-inositol (17), 1,3,5-O-(orthoformate)-myo-inositol (18) and 2-benzyl-1,3,5-O-(orthoformate)-myo-inositol (19). The X-ray diffraction structure of compounds 2, 6-8, 18 and 19 are reported.

     

Sulfonate protecting groups. Synthesis of O- and C-methylated inositols: d- and l-ononitol, d- and l-laminitol, mytilitol and scyllo-inositol methyl ether

Syntheses of d- and l-ononitol, d- and l-laminitol, mytilitol and scyllo-inositol methyl ether starting from myo-inositol are described. One or two of the myo-inositol 1,3,5-orthoformate hydroxyl groups were protected as tosylates. These mono or ditosylates served as key intermediates for the preparation of O- and C-methyl inositols. Racemic 2,4-di-O-tosyl-myo-inositol 1,3,5-orthoformate was resolved as its diastereomeric camphanates. Use of sulfonate groups for the protection of inositol hydroxyl groups resulted in substantial improvement in the overall yield of O- and C-methyl inositols.     

A flow-injection method for the amperometric determination of l-lactate with immobilized enzymes and a chemically modified electrode

A sensitive flow-injection system for l-lactate is described. Lactate dehydrogenase, LDH, and glutamic-pyruvic transaminase, GPT, were co-immobilized on a gluteraldehyde-activated porous silica support and used in a packed-bed enzyme reactor. l-lactate is oxidized to pyruvate in the presence of NAD⁺, an equivalent amount of NADH being produced. The equilibrium of the reaction is unfavourable, but by co-immobilizing LDH with GPT and adding l-glutamate, the pyruvate reacts and enough force is obtained to drive the oxidation of l-lactate totally to the product side. The NADH formed is then detected electrocatalytically at an electrode chemically modified with Meldola Blue, operated at 0 mV vs. Ag/AgCl. The system responds linearly to injected samples (25 μl) of l-lactate in the concentration range 10 μM–1.5 mM. The maximum sample throughput is 30 h^?1. The LDH/GPT reactor was stable for four weeks when used daily at optimal pH 8.8.     

l-α-Phosphatidyl-d-myo-inositol 3,5-bisphosphate: total synthesis of a new inositol phospholipid via myo-inositol orthoacetate

The synthesis from myo-inositol of a newly-discovered inositol phospholipid, phosphatidylinositol 3,5-bisphosphate [PtdIns(3,5)P₂], is described. The synthetic strategy, employing inter alia, a trimethylaluminium-mediated regioselective cleavage of a protected myo-inositol orthoacetate followed by an optical resolution using (R)-(−)-5-oxo-2-tetrahydrofurancarboxylate esters, allows rapid access to dipalmitoyl PtdIns(3,5)P₂.     

Total synthesis of the proposed structure of `brahol' and the structural revision

Proposed structure of brahol, a natural product, has been disproved by total synthesis of the proposed molecule from myo-inositol. Readily available 1,2;4,5-di-O-isopropylidene-myo-inositol, 3 was converted to 2,5-di-O-acetyl-1,6;3,4-di-O-isopropylidene-allo-inositol by epimerization of the di-triflate of 3. The acetyl group at O-5-position was selectively deprotected by aminolysis or methanolysis enabling the total synthesis of 5-O-methyl-allo-inositol, the proposed structure of brahol in six steps from myo-inositol. A comparison of spectral data of synthetic 5-O-methyl-allo-inositol with that reported for natural brahol revealed that the proposed structure of brahol is incorrect. A detailed structural revision revealed that brahol is nothing but quebrachitol. This study contradicts the first and only report on the natural occurrence of allo-inositol derivative.     

Total syntheses of cyclitol based natural products from myo-inositol: brahol and pinpollitol

Inositol and their derivatives are important class of biologically active natural products. Among the nine theoretically possible inositols, six are known to occur in nature. Interestingly one or more methyl ethers of these inositols have been isolated from plants and these methyl inositols are presumed to have important functions in plant biology. Brahol and pinpollitol are two naturally occurring methylated inositols reported to have allo-inositol and chiro-inositol configurations, respectively. Adopting our sulfonate inversion strategies for synthesizing protected chiro- and allo-inositols from cheaply available myo-inositol in combination with new methods we have achieved the total syntheses of these methylated inositols. The proposed structure of brahol has been synthesized in six steps from myo-inositol. We have not only disproved the proposed structure of brahol but also established its correct structure. Also, we have efficiently synthesized pinpollitol and its positional isomer from myo-inositol. These works involve several selective protection-deprotection strategies of inositol hydroxyl groups.     

Regioselective phosphorylation of vicinal 3,4-hydroxy myo-inositol derivative promoted practical synthesis of d-PtdIns(4,5)P2 and d-Ins(1,4,5)P3

The reactivity of 3 and 4-OH in 3,4-diol myo-inositol derivatives were observed through the phosphorylation, acylation and silylation. The results indicated that 3-OH is much more reactive than 4-OH, giving regiospecifically 3-mono-functionalized products. This investigation provided a concise methodology for the synthesis of natural d-form of PtdIns(4,5)P2 and d-Ins(1,4,5)P3 from l-1,2-O-cyclohexylidene-3,4-O-(tetraisopropyl disiloxane-1,3-diyl)-myo-inositol.     

Chelation controlled regiospecific O-substitution of myo-inositol orthoesters: convenient access to orthogonally protected myo-inositol derivatives

A general method for the completely regioselective protection of the three secondary hydroxyl groups of orthoester derivatives of myo-inositol, utilizing the subtle differences in reactivity exhibited by its alkali metal alkoxides due to differences in their ability to form chelates, is described. This method provides convenient access to orthogonally protected myo-inositol derivatives. A comparison of the methylation of racemic 4-O-trityl-myo-inositol 1,3,5-orthoformate in the presence of sodium or lithium ions showed that stabilization of the C4-alkoxide by chelation with lithium overrides steric hindrance offered by the C6-axial substituent in deciding the regioselectivity during the nucleophilic O-substitution.     

Continuous Flow Determination of Blood Alcohol Using Biamperometric Monitoring of Enzymatic Reaction

Abstract

Ethanol was determined by reaction with NAD in the presence of alcohol dehydrogenase in a continuous flow system. NADH produced was allowed to react with hexacyanoferrate (III) in the presence of diapharase. The concentration of the produced hexacyanoferrate (II) was monitored biamperometrically using open tubular carbon electrodes. A level of 1.5 × 10² mg/100 ml ethanol was detected, with an average precision of 4% relative standard deviation. The ethanol level in blood samples was determined, obtaining a 0.08 correlation coefficient with gas chromatography results.     

A formal synthesis of valiolamine from myo-inositol

An efficient formal synthesis of racemic valiolamine starting from readily available myo-inositol is reported. In all the synthetic steps only one regioisomer is formed, which circumvents laborious purification of products. Regioselective benzylation of myo-inositol orthoformate, super-hydride mediated deoxygenation of a cyclitol derivative and stereoselective addition of dichloromethyllithium to an inosose are the key reactions in the synthesis.     

Lactate biosensor based on human erythrocytes

An amperometric lactate biosensor based on human erythrocytes is described. The erythrocyte suspension is retained near the platinum electrode by means of a semipermeable membrane. The response is based on lactate dehydrogenase activity in the erythrocytes and uses the oxidation of NADH by hexacyanoferrate(III) and amperometric detection of the resulting hexacyanoferrate(II). The limit of detection is 2.8 × 10^?5 mol l^?1, and the response is linear up to 1 mmol l^?1 lactate in the analyzed solution (11 mmol l^?1 in a blood sample). The response time is 7 min, and the useful lifetime is 2 weeks. The response is influenced only by reducing substances (uric acid) and malic acid. The effect of uric acid is readily compensated, and there is insufficient malic acid in blood to affect the results.     

Syntheses of D-Myo-Inositol-1,2,6-Trisphosphate and -2,6-bisphosphate

Abstract

A D-myo-inositol derivative (3), obtained from methyl α-D-glucopyranoside by Ferrier rearrangement, was efficiently transformed to D-myo-inositol 1,2,6-trisphosphate (1, α-trinositol) and D-myo-inositol 2,6-bisphosphate (2).