The Faraday rotation of diamagnetic liquids has been measured by applying a pulsed magnetic field. The observed results for water, alcohol, and aliphatic and aromatic organic liquids suggested a possible discrimination of such liquids by Faraday imaging. Actually, we have succeeded to observe Faraday images using a magneto-optical microscope system. The discrimination of several diamagnetic liquids including chiral liquids has been demonstrated.
To overcome the ensemble-averaging barrier, single-molecule experiments have been performed, but energy landscapes comprising multiple intermediates have not yet been defined. We performed mechanical unfolding of staphylococcal nuclease using intermolecular force microscopy, modified AFM with high resolution and feedback control of the positioning. The force dropped vertically just after its peak, and multiple transition states were detected as force peaks. The multiple and stochastic intermediates found in the present study provide new important information on protein folding.
Photochromic crown compounds, such as monomeric and polymeric crown compounds incorporating spirobenzopyran, spironaphthooxazine, spirobenzothiapyran, Malachite Green, and Crystal Violet moieties, were synthesized for applications in the fields of analytical and separation chemistry. The photochromic crown compounds, especially crowned spirobenzopyran derivatives, were applied to metal ion extraction, extraction spectrophotometry, membrane transport, and ion chromatography, the sensitivity and selectivity of which were controlled and enhanced photochemically. Also, micelles and vesicles containing lipophilic crowned spirobenzopyrans and Malachite Greens were tested for their usefulness in spectrophotometric and fluorometric metal-ion determination and photocontrol of organic substance in aqueous systems. The polymeric crowned spirobenzopyrans were tried to use as a photochemical valve based on photochemical rheology changes. Moreover, attempts were made to directly observe photoinduced aggregation of the spirobenzopyran moiety and photoresponsive rheology changes of the polymeric crowned spirobenzopyran, by using chemical force microscopy.
This review describes a comprehensive investigation focusing on syntheses of analytical reagents, followed by their utilization in development of analytical methods, and leading to practical applications for rational use of medicaments centering on abused drugs. Many kinds of analytical reagents for fluorescence and chemiluminescence detections have been synthesized with the intention of improving sensitivity. By properly combining the developed analytical reagents with an HPLC separation technique, one could determine ultra-small amounts of abused drugs such as stimulants, narcotics and obesity drugs in various matrices. Furthermore, chiral analyses of some abused drugs and evaluation of their potential for drug-drug interaction were also performed. The developed methods might be useful for forensic and toxicological studies on drug abuse. Also, the results obtained in our study might contribute to the prediction of and the protection of human health from risks of abused drugs.
The potentiometric response of electrodes is described, including: (1) Nernstian response to activity change due to an altered concentration of the analyte ion, and (2) Nernstian response to activity change caused by different solvents. In order to ensure the reliability of the data obtained in this study, the following three steps were taken: (i) a comparison of electrode potentials between a monovalent cation-sensitive glass electrode and amalgam electrodes; (ii) a comparison of the data with those obtained by other methods; and (iii) a comparison of the data obtained by employing different reference solvents. This review also describes the development of electrodes, including the synthesis of host compounds by esterification and amide bonding with poly(acrylamide), thermodynamic application results obtained by the developed electrodes, and brief discussions about the response mechanism and an establishment site of the membrane potential.
A technology to display proteins or peptides on living organisms has been developed over the last two decades. So-called “Molecular display (Arming) technology” or “Cell surface engineering” has been one of the important tools for analyzing and understanding protein function, or for screening of novel clones from libraries. In addition, it endows cells with novel abilities that cannot be added by conventional genetic recombination. In particular, the yeast Saccharomyces cerevisiae has a lot of advantages in molecular display technology. Normal yeast cells can be transformed into a wide variety of “arming yeasts” that have catalytic functions, affinity binding to valuable ligands, bioremediation properties, bio-monitoring properties, etc. This review describes the background, applications, and representative achievements of molecular display technology of yeast.
Chitosan resin possessing the 4-hydroxyphthalic acid moiety (CCTS-HPA resin) was synthesized. This resin could adsorb chromium(VI) at pH 3 to 5, whereas chromium(III) could not be retained in the acidic region. The CCTS-HPA resin was used for collecting chromium(VI), and ME-03 resin was used for collecting chromium(III) before their measurement by ICP-AES measurement. Both resins were packed in mini-columns and installed serially in a laboratory-assembled automated pretreatment system (Auto-Pret System). The system provides a highly sensitive and fully automated procedure for the speciation of chromium(III) and chromium(VI). The proposed system was successfully applied to speciation of chromium(III) and chromium(VI) using 5 ml of water samples. The detection limits (S/N = 3) of chromium(III) and chromium(VI) were 0.06 and 0.04 µg l-1, respectively, along with an analysis time of 7 min 45 s for both chromium species. The lowest determinable concentrations for both chromium species were about 0.5 µg l-1, which was enough for the speciation of chromium in water samples.
A simple and sensitive determination method for selenomethionine (Se-Met) using an HPLC-fluorescence detection system coupled with an on-line electrochemical reactor has been developed. NBD-F (4-fluoro-7-nitro-2,1,3-benzoxadiazole) was used as the fluorescent derivatization reagent for Se-Met. NBD-Se-Met was separated from NBD-derivatives of 22 other amino acids within 35 min. Applying an optimized oxidation potential enhanced the fluorescence intensity of NBD-Se-Met 10-fold. The calibration curve was linear in the range of 300 fmol to 30 pmol with a correlation coefficient of 0.997. Detection limit (S/N = 3) was calculated to be 50 fmol, which is comparable to that of inductively coupled plasma mass spectrometry. This simple and sensitive method should be useful for the determination of Se-Met in physiological samples, such as serum or urine.
A technique for detecting ion suppression in LC/MS was developed by adding a specific concentration of a probe molecule to an LC mobile phase. The probe is sufficiently acidic and hydrophilic, such that the intensity of the protonated probe, as analyzed in a mass spectrometer, is expected to decrease much more than those of other analytes when ion suppression occurs. Thus, the potential occurrence of ion suppression is detected by monitoring the intensity of the protonated probe. However, the probe has been developed for limited conditions of the LC mobile phase used in proteomics. In this paper, we examine the probe’s applicability to the experimental conditions used in pharmacokinetics and drug metabolism. Our results demonstrate that the probe can be used in mobile phases, in which the pH ranges from 1.8 to 6.7 and the organic solvent concentration ranges from 10 to 90%. Furthermore, the detection of ion suppression in the analysis of Omeprazole in human plasma was demonstrated by increasing the amount of the plasma in the sample solution.
This paper describes a new method for the rapid and sensitive analysis of atrazine and simazine based on the dispersive liquid-liquid microextraction with carbon tetrachloride and methanol as the extraction solvent and disperser solvent. Under the optimal conditions, there are excellent linear relationships between the peak area and the concentration in the range of 0.5 - 50 µg L-1 for atrazine and 0.1 - 50 µg L-1 for simazine. The limits of detection were 0.1 and 0.04 µg L-1 for atrazine and simazine, respectively. The proposed method was also applied to the analysis of real water samples, and excellent results were achieved with spiked recoveries in the range of 60.7 - 91.4%. All these results demonstrate that the proposed method would be widely used in many fields in the future.
A metal extraction system using fluorous solvents has been developed. Perfluorinated β-diketone, 1,1,1,5,5,6,6,6-octafluoro-2,4-hexanedione (C6F8βDK) dissolves in the fluorous solvent FC-72 and can extract transition metal ions from water into FC-72. The extraction efficiency in the FC-72 system is comparable to that of chloroform. By using the immiscibility of FC-72 with conventional organic solvents, metal extraction was also achieved from acetonitrile and dioxane. Metal ions extracted into FC-72 can be readily stripped using 1 M nitric acid. We succeeded in a colorimetric assay of metal ion concentration in water and in organic solvents by contacting each solvent with FC-72 containing C6F8βDK. Iron ions with different concentrations (0 - 0.1 mM) in water or acetonitrile are completely extracted into FC-72 to form a Fe3+-C6F8βDK complex, which can be detected by spectrophotometry due to its absorption in the UV-vis region. We have demonstrated that fluorous solvents would be promising candidates for a novel separation and analytical medium for metal ions.
Indole-3-acetic acid (IAA) is a phytohormone of the auxin group and is capable of coordinating the overall processes of plant growth and development. IAA is active in the very low concentration range. Therefore, it is important to quantify IAA in the low concentration range in complex system. In this work, a new spectrofluorometric method for the direct determination of IAA in soil is proposed and discussed. It combines the fluorescence excitation-emission matrices (EEMs) with second-order calibration methods based on the alternating trilinear decomposition (ATLD) algorithm and the self-weighed alternating trilinear decomposition (SWATLD) algorithm. These methodologies fully exploit the second-order advantage of the three-way fluorescence data, allowing the analyte concentrations to be quantified even in the presence of unknown fluorescent interferents. IAA recoveries in soil were determined as 100.6 ± 3.0 and 96.9 ± 1.1% with ATLD and SWATLD, respectively. The limits of detection obtained were 17.6 and 4.6 ng mL-1, and the limits of quantification were 52.9 and 13.9 ng mL-1 with ATLD and SWATLD, respectively.
A novel and simple spectrophotometric method for the determination of tiopronin with sodium 1,2-naphthoquinone-4-sulfonate (NQS) is established in this paper. The detailed mechanism is proposed and discussed. It is based on the fact that tiopronin can catalyze the reaction between sodium 1,2-naphthoquinone-4-sulfonate and hydroxyl ion to form 2-hydroxy-1,4-naphthoquinone in a buffer solution of pH 13.00 at the maximal absorption wavelength of 445 nm. When tetradecyl benzyl dimethyl ammonium chloride (Zeph) is added to the solution, the sensitivity of the reaction is improved. Beer's law is obeyed in a range of 0.39 - 15.67 µg mL-1. The equation of linear regression is A = 0.11749 + 0.05914C (µg mL-1), with a linear correlation coefficient of 0.9973. The detection limit is 0.2 µg mL-1, RSD is 0.88% and the recovery rate is in the range of 96.6 - 103.9%. Furthermore, the method has been validated and successfully applied to the determination of tiopronin in pharmaceutical samples.
Microwave-assisted acid decomposition and oil-in-water emulsification were evaluated as sample pretreatment procedures to determine Al, Ba, Mo, Si and V in lubricating oils by high-resolution continuum source flame atomic absorption spectrometry (HR-CS FAAS). Average recoveries of Al, Ba and V in oil digests (107, 103 and 101%) were close to those obtained for emulsions prepared in kerosene medium (94, 113 and 95%). Average recoveries for Mo were close to 105 and 46% for emulsions and digests, respectively. Improved average recoveries (101%) were obtained for Mo in digests using the analyte addition technique. Silicon was successfully quantified only in digested samples. Limits of quantification for Al, Ba, Mo and V were 1.4, 31.5, 1.5 and 11.4-fold lower than those obtained by line-source FAAS. Enhanced sensitivity, multi-elemental capability, and high sample throughput are among the main advantages of HR-CS FAAS in comparison with the line-source FAAS technique.
We report on the use of sensing devices that have a metal-insulator-gap-insulator-semiconductor structure. We have used capacitance-voltage measurements from a metal-insulator-gap-insulator-semiconductor sensing device to characterize different pH solutions and deoxyribonucleic acid (DNA) solutions. Hysteresis in the capacitance-voltage curves results from mobile ionic charges in the solutions and the influence of changes on the sensing surface condition. As the pH decreases in the pH range of 2.7 to 7.0, the flatband voltage shift toward the negative voltage increases. The differences in the flatband voltage shift in capacitance-voltage curves are related to the mobile ionic charge density in solutions with different pH values or DNA molecules.
The redox activity of a chitin film on a glassy carbon electrode was remarkably improved by the addition of carbon powder to the film in the detection of ascorbic acid, flavin adenine dinucleotide (FAD) and nicotinamide adenine dinucleotide (NADH). Although oxidation of ascorbic acid using the electrode with the chitin film did not give an appreciable voltametric response, the addition of carbon powder to the film greatly improved its activity up to a 95% level of the bare carbon electrode. For FAD and NADH, an increase in each oxidation peak was observed in a similar manner. The improvement was due to electron mediation of the carbon powder contained in the film. Thus, the electrode effectively recovers the sensitivity for some biological molecules, and thus becomes a powerful device to monitor reactions between biological molecules. Because both carbon and chitin are materials with high biocompatibility, the film can be considered as cell scaffolds. Furthermore, the film immobilized on the plate has a possibility as an electrode in itself.
In this report, we have developed a novel quantitative RT-PCR protocol in which the procedure including mRNA purification can be performed in an all-in-one tube. To simplify gene expression analysis, oligo-dT30 immobilized PCR tubes were used serially to capture mRNA, synthesize solid-phase cDNA, and amplify specific genes. The immobilized oligo-dT30 can efficiently capture mRNA directly from crude human cell lysates. The captured mRNA is then amplified by one-step reverse transcription PCR (RT-PCR) with initial cDNA synthesis followed by PCR. In RT-PCR, this new reusable PCR tube device can be employed for multiple PCR amplifications with different primer sets from a solid-phase oligo-dT30 primed cDNA library. This paper introduces a novel and highly reliable all-in-one tube method for rapid cell lysis, followed by quantitative preparation and expression analysis of target mRNA molecules with small amounts of sample. This procedure allows all steps to be carried out by sequential dilution in a single tube, without chemical extraction. We demonstrate the utility of this novel method by quantification of two housekeeping genes, β-actin and GAPDH, in HeLa cells. We believe this new PCR device can be useful as a platform for various mRNA expression analyses, including basic research, drug screening, and molecular toxicology, as well as for molecular pathological diagnostics.
Two fluorescence modes were combined to analyze the binding properties of terminally substituted alkanes (CnX, X = COOH, OH, CHO, NH2) to human serum albumin (HSA). A competitive binding assay using an 8-anilino-1-naphthalenesulfonate (ANS) fluorescence probe provides information on all the hydrophobic binding sites in HSA. A binding assay using the intrinsic fluorescence of the tryptophan residue in HSA (Trp-HSA) provides information on the specific binding site close to the tryptophan residue. There are three fluorescence-active ANS binding sites in HSA, which can be classified into two types by their affinity for ANS. CnCOOH bound to all three ANS binding sites including the Trp-HSA site, however, it did not quench the fluorescence of Trp-HSA. CnCHO bound only to the Trp-HSA site with quenching of the fluorescence of Trp-HSA. By comparing the binding affinities of HSA for CnOH and CnCHO, it was concluded that the CnOH binding site is different from the CnCHO binding site. CnNH2 did not bind to any of the three ANS binding sites in HSA.
Inorganic thallium compounds in the atmospheric particulate matter of emissions and in the workplace air of specific industrial production can be determined through selective sequential extractions: Tl(I) is separated from Tl(0) and Tl(III) in the first step, Tl(0) in the second one, while in the final extraction both Tl(III) soluble and insoluble compounds are determined. The procedure has been tested on 1633a Coal Fly Ash standard reference material. The thallium recovery was in the range 91 - 98%.
A simple and sensitive spectrophotometric method for the determination of quinolone antibiotics was established based on an association complex formation with aluminum(III) and erythrosin. In the determination of ofloxacin as a quinolone antibiotic, Beer's law is obeyed in the range of 0.1 - 3.2 µg ml-1, with an effective molar absorptivity at 555 nm and the relative standard deviation being 1.2 × 105 L mol-1 cm-1 and 0.9% (n = 6). This method was successfully applied to the assay of quinolone antibiotics in pharmaceutical preparations.
A sensitive and simple color sensor for indole vapors has been developed based on the Ehrlich-type reaction in solid polymer film. Upon 60-min exposure of the film sensor to the air containing 5 - 100 ppb of indole vapors, pink or magenta color could be recognized by the naked eyes. Alternatively, a trial gas detector tube has been prepared by mixing the reagents with sea sand. When air (100 mL) was pumped through the detector tube, indole vapors above 20 ppb could be detected within 1 min. The sensing was selective to the vapors of indoles and pyrroles, and other VOCs or ambient moisture did not interfere.
Several methods are proposed to check the sealing of a magic-angle-spinning (MAS) rotor. The intrusion of moisture into the MAS rotor is checked by trimethylphosphine oxide, which is highly hygroscopic. Its hydrated form is separately observed in 31P MAS NMR spectra from the crystalline (anhydrous) form. 1H MAS NMR can monitor the hydrated form, the crystalline form, and adsorbed water independently. Gas leakage from the MAS rotor is monitored by measuring 129Xe MAS NMR spectra of xenon (Xe) confined in zeolites as well as 3He MAS NMR spectra of 3He gas. The sealing effect of MAS rotors has been checked quantitatively using the above methods.
Thirty elements in garlic sample were determined by inductively coupled plasma mass spectrometry (ICP-MS) and inductively coupled plasma atomic emission spectrometry (ICP-AES) after microwave digestion. The concentrations of K, Ca,Na, Sr, and Hg in the present garlic sample were higher than those in rice and wheat, but the concentration of Se in the garlic sample was relatively lower. The extractability of the elements in the garlic sample was also examined; the results showed that most of the elements could be easily extracted by pure water and/or a 0.1 M HNO3 solution, except for Hg. Furthermore, the size-fractional distribution of the elements in garlic was investigated by pure water extraction and centrifugal ultrafiltration.