Electrochemical Detection of Sesamol Dimer and its Application to Measurement of Radicals.

In this paper we propose a novel measurement for NO and ·OH by electrochemical detection using sesamol. Standard samples of the sesamol monomer and dimer were subjected to differential pulse voltammetry, resulting in their peaks being clearly separated and detected. Based on the oxidative dimerization of sesamol, the current simple, sensitive and selective method was successfully applied to preliminary measurements for NO and ·OH, respectively.

Binding Assays Using a Benzofurazan-Labeled Fluorescent Probe for Estrogen Receptor-Ligand Interactions.

Binding assays are widely used to study the estrogenic activity of compounds targeting the estrogen receptor (ER). The fluorescence properties of benzofurazan (BD), an environmentally sensitive fluorophore, are affected by solvent polarity. In this study, we synthesized BD-labeled estradiol (E2) derivatives hoping to develop a fluorescent ligand to be used in ER binding assays, without the separation of free- from bound-ligand.

Proton Affinitive Derivatization for Highly Sensitive Determination of Testosterone and Dihydrotestosterone in Saliva Samples by LC-ESI-MS/MS.

In this study, proton affinitive derivatization using picolinic acid and its analogs (3- and 6-methylpicolinic acid and 5-butylpicolinic acid) with proton affinitive moieties was performed for the highly sensitive determination of testosterone (T) and 5α-dihydrotestosterone (DHT) in saliva by LC-ESI-MS/MS. T and DHT were converted to their corresponding picolinate esters and their chromatographic behavior was investigated with a reversed phase column. The picolinate ester of each steroid exhibited a clear single peak and elution occurred in the following order: picolinate, 3/6-methylpicolinate, and 5-butylpicolinate.

Recent development of chemical derivatization in LC-MS for biomedical approaches.

LC-MS/MS is currently the most powerful system in biomedical analysis. At the same time, chemical derivatization is a useful technique to enhance the detection sensitivity of nonionizable or poorly ionizable molecules in LC-MS/MS. Derivatization improves the ionization efficiency, the chromatographic separation and/or the chemical stability.

Development of a highly sensitive chemiluminescent assay for hydrogen peroxide under neutral conditions using acridinium ester and its application to an enzyme immunoassay.

We developed a highly sensitive chemiluminescent (CL) assay for hydrogen peroxide using 10-methyl-9-(phenoxycarbonyl) acridinium fluorosulfonate (PMAC) that produced chemiluminescence under neutral conditions and applied it to an enzyme immunoassay (EIA). One picomole of hydrogen peroxide could be detected using the optimized PMAC-CL method and 6.2 × 10(-20) mol β-D-galactosidase (β-gal) could be detected by combining an indoxyl derivative substrate and the proposed PMAC-CL method.

New fluorimetric assay of horseradish peroxidase using sesamol as substrate and its application to EIA.

Horseradish peroxidase (HRP) is generally used as a label enzyme in enzyme immunoassay (EIA). The procedure used for HRP detection in EIA is critical for sensitivity and precision. This paper describes a novel fluorimetric assay for horseradish peroxidase (HRP) using sesamol as substrate.

Development of RNA aptamer and its ligand binding assay on microchip electrophoresis.

Microchip electrophoresis (ME) coupled with fluorescence detection was used to estimate the binding activity of aptamer in each systematic evolution of ligands by exponential enrichment (SELEX) round for a target molecule. This approach is a non-radioisotopic, rapid and simple platform, and electrophoretic separation appears to be an effective technique for aptamers of oligonucleotide molecules. We tried to obtain gonadotropin-specific RNA aptamer by the above approach.

Low-cost fluorimetric determination of radicals based on fluorogenic dimerization of the natural phenol sesamol.

A novel fluorimetric method for determining radicals using the natural phenol sesamol as a fluorogenic reagent is reported. In this assay, sesamol was reacted with aqueous radicals to yield one isomer of a sesamol dimer exclusively. The dimer emitted purple fluorescence near 400 nm around neutral pH, where it assumed the monoanionic form.

Development of a novel fluorometric assay for nitric oxide utilizing sesamol and its application to analysis of nitric oxide-releasing drugs.

Nitric oxide (NO) is related to various physiological effects as well as to numerous diseases caused by accentuation of NO production. Measurement of NO in cells and tissues is difficult as NO readily reacts with other molecules; furthermore, its half-life as a radical is fleeting. Currently, many NO pharmaceuticals are marketed as therapeutic agents for ischemic disease.

Microfluidics: applications for analytical purposes in chemistry and biochemistry.

In this review, we present recent advancements and novel developments in fluidic systems for applied analytical purposes in chemistry, biochemistry, and life science in general that employ and reflect the full benefits of microfluidics. A staggering rise in publications related to integrated, all-in-one microfluidic chips capable of separation, reaction, and detection have been observed, all of which realise the principal of micro total analysis systems or lab-on-a-chip. These integrated chips actively adopt the scaling law concepts, utilising the highly developed fabrication techniques.

Modulation of coactivator recruitment by cooperative ligand binding to human Estrogen receptor alpha and beta.

Estrogen receptor (ER) is a member of the nuclear receptor superfamily, and functions as a ligand-dependent transcription factor with roles in cell growth and differentiation. In addition to endogenous estrogen, 17beta-estradiol (E(2)) and artificial antagonists, many suspected environmental estrogenic chemicals are reported to bind to ER, with various affinities and transcriptional responses. ER is also an allosteric protein and shows a positive cooperative interaction with E(2).

Study on interactions of endocrine disruptors with estrogen receptor using fluorescence polarization.

In this study, we examined the affinities of many (21) compounds such as hormones, pharmaceuticals, industrial chemicals, and phytoestrogens to the estrogen receptor (ER) by ER binding assay using fluorescence polarization (FP). This method is based on the competitive binding assay using fluorescein-labeled estradiol (F-E2), in which the polarization values decreased with the addition of the compounds (competitors). The obtained sigmoidal inhibition curves were transformed into the pseudo-Hill plots, and the concentrations at 50% inhibition (IC50) and Hill coefficients were obtained from the regression equations.

Study on interactions of endocrine disruptors with estrogen receptor-beta using fluorescence polarization.

In this study, we developed a rapid, simple and homogeneous human recombinant estrogen receptor-beta (hrER-beta) binding assay method using fluorescence polarization (FP) by applying a fluorescent ligand, fluorescein-labeled estradiol (F-E2). A Scatchard plot and a Hill plot analysis of the saturation binding assay using F-E2 and hrER-beta were studied. F-E2 showed a high affinity for hrER-beta, the dissociation constant was 5.

Development of hydrophilic fluorogenic derivatization reagents for thiols: 4-(N-acetylaminosulfonyl)-7-fluoro-2,1,3-benzoxadiazole and 4-(N-trichloroacetylaminosulfonyl)-7-fluoro-2,1,3-benzoxadiazole.

Sensitive, reactive, and hydrophilic fluorogenic reagents for thiols with the benzofurazan skeleton, 4-(N-acetylaminosulfonyl)-7-fluoro-2,1,3-benzoxadiazole (AcABD-F) and 4-(N-trichloroacetylaminosulfonyl)-7-fluoro-2,1,3-benzoxadiazole (TCAcABD-F) have been developed. These reagents reacted with thiols within 10 min at 60 degrees C. AcABD-F and TCAcABD-F themselves do not fluoresce but are strongly fluorescent after the reaction with thiol compounds.

Estrogen receptor binding assay method for endocrine disruptors using fluorescence polarization.

A rapid, simple and nonhazardous assay method for endcrine disruptors was developed using an estrogen receptor (ER) and fluorescence polarization (FP). Among the fluorescent compounds, the 17alpha-fluorescein-labeled estradiol derivative was selected as the most suitable ligand for the ER binding assay, since it showed the highest affinity to ER. In the Scatchard plot analysis, its convex curve exhibited a positive cooperative binding, indicating the induction of a conformational change of the ER with the binding of the ligand to form a dimer and to increase the affinity for the additional ligand.