Metal complexes of functionalized cyclodextrins as enzyme models and chiral receptors

N-aminobutyl-N-ethylisoluminol and horseradish peroxidase bifunctionalized graphene oxide hybrids (ABEI-GO@HRP) were prepared through a facile and green strategy for the first time. The hybrids exhibited excellent chemiluminescence (CL) activity over a wide range of pH from 6.1 to 13.0 when reacted with H2O2, whereas ABEI functionalized GO had no CL emission at neutral pH and showed more than 2 orders of magnitude lower CL intensity than ABEI-GO@HRP at pH 13.0. Such strong CL emission from ABEI-GO@HRP was probably due to that HRP and GO facilitated the formation of O2•–, – CO4•2–, HO•, and π-C═C• in the CL reaction, and GO as a reaction interface promoted the electron transfer of the radical-involved reaction. By virtue of ABEI-GO@HRP as a platform, an ultrasensitive, selective, and reagentless CL sensor was developed for H2O2 detection. The CL sensor exhibited a detection limit of 47 fM at physiological pH, which was more than 2 orders of magnitude lower than previously reported methods. This work reveal...

Highly Chemiluminescent Graphene Oxide Hybrids Bifunctionalized by N-(Aminobutyl)-N-(Ethylisoluminol)/Horseradish Peroxidase and Sensitive Sensing of Hydrogen Peroxide

A novel detection method for catecholamines using imidazole was investigated using a chemiluminescence coupled flow injection system. Imidazole catalysed decomposition of catecholamines to generate hydrogen peroxide, then the hydrogen peroxide was detected by chemiluminescence. The optimal condition for generation of hydrogen peroxide from a catecholamine was to incubate the catecholamines (53 pmol) in an imidazole solution (50 mmol/L, pH 9.0, 1.0 mL) at 60°C for 30 min. Peroxide­was detected by peroxyoxalate chemiluminescence, and the rank order of the light emission intensities was as follows; dopamine (100%) >epinephrine (78%) >L-DOPA (62%) >norepinephrine (58%) >deoxyepinephrine (51%) >isoproterenol (43%) >dihydroxybenzylamine (25%). The light intensities of the reaction mixtures (corresponding to 1.06 pmol catecholamines) varied depending on the chemiluminescence (CL) detection reaction, and the rank order of the light intensity was as follows; luminol CL catalysed with horseradish peroxidase (HRP) (371%) >peroxyoxalate chemiluminescence (100%) >luminol CL catalysed with ferrycianide (62%) >lucigenin CL (15%) >pyrogallol CL (0.8%) >purpurogallin CL (0.4%) >luminol CL (0.3%). The luminol CL reaction catalysed by HRP is recommended for the detection of peroxide in this method for catecholamines. Copyright © 1999 John Wiley & Sons, Ltd.

Chemiluminescent detection of catecholamines by generation of hydrogen peroxide with imidazole

http://www.ics.ee.nctu.edu.tw/~mdker/Referred%20Journal%20Papers/Ker_Biosensors_and_Bioelectronics_Jun_2007.pdf

Fabrication of a miniature CMOS-based optical biosensor.

A miniaturized polymer electrospray-type interface is used to study metal-ion chelation with model peptides. Taking advantage of the intrinsic electrochemical behavior of electrospray, a sacrificial electrode is used to generate at the same time electrospray and transition-metal ions coming from the anodic dissolution of the electrode. The microspray interface provides enhanced mass transport due to its small dimensions, increasing the yield of possible reactions, in particular complex formation. Transition-metal electrodes, e.g. copper, zinc, nickel, iron and silver, are used to obtain on-line complexation with model peptides. It is demonstrated that the use of in-reservoir sacrificial electrodes is an efficient way to generate metal ions in order to form and study complexes with peptides, avoiding the addition of metallic salts.

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Study of peptide on-line complexation with transition-metal ions generated from sacrificial electrodes in thin-chip polymer microsprays.

Hydrogen peroxide formed during the course of the copper(II)-catalysed oxidation of cysteamine with oxygen was continuously determined by a peroxidase (POD)-catalysed luminol chemiluminescence (CL) method. Horseradish peroxidase (HRP), lactoperoxidase (LPO) and Arthromyces ramosus peroxidase (ARP) were used as a CL catalyst. The respective PODs gave specific CL intensity-time profiles. HRP caused a CL delay, and ARP gave a time-response curve which followed the production rate of H2O2. LPO gave only a weak CL flash which decayed promptly. These differences of CL response curves could be explained in terms of the different reactivities of PODs for superoxide anion and the different formation rate of luminol radicals in the peroxidation of luminol catalysed by POD.

Characterization of peroxidases in luminol chemiluminescence coupled with copper-catalysed oxidation of cysteamine.

(2-Mercaptoethyl)amino-attached cyclodextrin provides a highly enantioselective environment during the transformation of phenylglyoxal into (S)-mandelic acid, although simple inclusion into native α-,β-, and γ-cyclodextrins and their 2-hydroxypropyl and methyl variants is not sufficient to cause appreciable asymmetric induction.

Asymmetric Transformation of Phenylglyoxal into Mandelic Acid Catalyzed by Cyclodextrin-Based Glyoxalase Models

Delayed chemiluminescence (CL) was observed in the copper(II)-catalyzed oxidation of cysteamine with oxygen in the presence of horseradish peroxidase (HRP) and luminol. After preferential catalytic oxidation of cysteamine by both Cu(II) and HRP, a HRP-catalyzed luminol CL reaction was subsequently commenced with hydrogen peroxide accumulated from the catalytic oxidation. Thus, a delay time from the reaction initiation to a sharp flash of CL was observed. The HRP-catalyzed CL-delay of luminol was applied to the determination of Cu(II). The delay time was linearly correlated with the Cu(II) concentration over the range from the detection limit of 5.0 × 10−9 to 1.5 × 10−5 M. The detection limit of the present method is a factor of 30 times better than that of the conventional luminol CL method. The relative standard deviation of the delay time in five successive experiments was 3.2% at 1.0 × 10−7 M of Cu(II). The present method was highly sensitive compared to the conventional luminol CL method.

Peroxidase-Catalyzed Chemiluminescence-Delay of Luminol for Determination of Traces of Copper(II)

A novel spectrophotometric method was developed for the determination of aliphatic thiols. The method was based on the stoichiometric redox reaction between aliphatic thiol and a copper(II) complex with 1, 10-phenanthroline in dimethyl sulfoxide to form an intensely colored copper(I) complex, which had a molar absorptivity of 7000dm3 mol-1 cm-1 at 444nm. The calibration curves for five aliphatic thiols of carbon numbers 1-8 had the same slope over the range from the detection limit of 5.0×10-6 to 1.5×10-4mol dm-3. The relative standard deviation of five successive experiments was 2.0% at 8.6×10-5mol dm-3 of 1-butanethiol. The method was applied to the determination of methanethiol in gas samples.

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Spectrophotometric Determination of Aliphatic Thiols Based on Redox Color Reaction with Copper(II) Complex of 1, 10-Phenanthroline in Dimethyl Sulfoxide

Atsushi Katayama

Papers

Characterization of peroxidases in luminol chemiluminescence coupled with copper-catalysed oxidation of cysteamine.

Asymmetric Transformation of Phenylglyoxal into Mandelic Acid Catalyzed by Cyclodextrin-Based Glyoxalase Models

Peroxidase-Catalyzed Chemiluminescence-Delay of Luminol for Determination of Traces of Copper(II)

Spectrophotometric Determination of Aliphatic Thiols Based on Redox Color Reaction with Copper(II) Complex of 1, 10-Phenanthroline in Dimethyl Sulfoxide

Asymmetric Transformation of Phenylglyoxal into Mandelic Acid Catalyzed by Cyclodextrin-Based Glyoxalase Models.