Color modulation for chemiluminescence of a dioxetane bearing a 3-(anthracen-9-yl)-5-hydroxyphenyl moiety induced by a complex of crown ether with potassium tert-butoxide

Color modulation was first observed for CT-induced chemiluminescent decomposition of a dioxetane bearing a 3-(anthracen-9-yl)-5-hydroxyphenyl induced by a complex of crown ether with potassium tert-butoxide in benzene system. The phenomenon is rationalized by conformational change of a biaryl moiety in the emitter, which is induced by steric interaction of anthryl and a plane of crown ether complex.     

Determination of streptomycin in serum by high-performance liquid chromatography

A high-performance liquid chromatographic method was developed for monitoring the serum concentration of streptomycin. The method includes clean-up using a Sep-Pak C18 cartridge and quantitation using dihydrostreptomycin as an internal standard. Streptomycin and dihydrostreptomycin were separated by reversed-phase ion-pair chromatography on LiChrosorb RP-18 and detected by UV absorption (195 nm). The calibration graph of serum streptomycin concentration was linear over the range 5-50 micrograms/ml. Streptomycin was added to serum at the level of 20.0 micrograms/ml and its concentration was determined to be 18.9 micrograms/ml with a coefficient of variation of 2.07% (n = 5). The clinical application of this method was confirmed by comparison with fluorescence polarization immunoassay.     

Thickening properties and emulsification mechanisms of new derivatives of polysaccharides in aqueous solution

The thickening properties of aqueous solutions of HHM-HEC (hydrophobically-hydrophilically modified hydroxyethylcellulose) and the emulsification mechanisms of HHM-HEC/water/oil systems were investigated. A dramatic increase in viscosity was observed with increased HHM-HEC concentration in water, caused by aggregation of hydrophobic alkyl chains. At higher concentrations of HHM-HEC (above 0.6 wt%) in water, it forms an elastic gel, which has good thixotropic properties and a high yield value. O/W (oil-in-water) type emulsions were obtained using HHM-HEC, which can emulsify various kinds of oil, including hydrocarbon, silicone, and perfluoropolymethylisopropyl ether. The viscosity of these emulsions depends only upon the oil volume fraction, not on the kind of oil. In addition, the oil particle size in the emulsions remained constant after a certain period because HHM-HEC formed a strong gel network structure and a protective layer, which prevented the emulsion from coalescing. Measurements of interfacial tension revealed that the alkyl chains in HHM-HEC did not significantly lower the interfacial tension at the water/oil interface when 0.5 wt% of HHM-HEC was added to water. Steady flow and oscillatory experimental results show that the rheological behavior of HHM-HEC/water/oil emulsions was similar to that of aqueous solutions of HHM-HEC. In the HHM-HEC/water/oil emulsion system, oil droplets were dispersed and kept stable in the strong gel structure of HHM-HEC. The aqueous solution of HHM-HEC showed salt resistance. It is thought to be due to sulfonic acid groups in HHM-HEC. The stability of the emulsion using HHM-HEC is based on both protective colloidal effects and associative thickening caused by alkyl chains in HHM-HEC.     

Synthetic studies on pyrroloquinolines. II. Studies on the syntheses and chemical properties of 1H-pyrrolo[2,3-b] quinolmes

This paper describes the syntheses and the properties of 1H-pyrrolo[2,3-6]quinolines derived from 2,3-dihydrofuro[3,2-c]quinolines or 3-(β-chloroethyl)-2,4-dichloroquinolines. The discrepancy on the physical data of 1H-pyrrolo[2,3-b]quinoline between our product and Perkin's previously reported product is also discussed.     

Entrainment in a chemical oscillator chain with a pacemaker

Entrainment by a pacemaker was investigated experimentally and numerically in a chain of chemical oscillators using coupled discrete Belousov-Zhabotinsky reaction oscillators. The spontaneous frequency of each oscillator depended on the concentration of catalyst ions. The coupling strengths among the nearest neighbor oscillators were controlled by changing the spacing distance (d) between beads. When the coupling strength was sufficiently strong, the pacemaker entrained other oscillators in the chain. Subsequently, the trigger waves propagating from a pacemaker were observed. The range of trigger wave propagation area, i.e., the number of entrained oscillators, depended on d. Numerical simulation for the system described the experimental results well. Furthermore, photic noise maximized the strength of entrainment at an optimal noise intensity.     

Investigation of an Olfactoryly Active Ring-Like Conformer of a Chain-Type Odorant, (3S)-3,7-dimethyloctanal,by computer calculation and graphics

The odor of (3S)-3,7-dimethyloctanal, a chain-type odorant, has some resemblance to that of ethyl (1 R, 6S)-2,2,6-trimethylcyclohexane-1-carboxylate, a ring-type odorant. We investigated the ring-like conformers of (3S)-3,7-dimethyloctanal. Two approaches, (i) systematic conformational analysis and (ii) construction of the initial structure by referring to the structure of the ring-type odorant, were considered in the search for ring-like conformers of the chain-type odorant. As a result, it was found that two stable ring-like conformers of (3S)-3,7-dimethyloctanal, obtained from the two approaches, resembled conformers of ethyl (1R, 6S)-2,2,6-trimethylcyclohexane-1-carboxylate in their three-dimensional structural features. The shapes of the two ring-like ones were not exactly the same but were quite similar. Therefore, the two ring-like conformers were considered to approximate the olfactoryly active conformer that binds and stimulates the same odor receptor as that for ethyl (1R,6S)-2,2,6-trimethylcyclohexane-1-carboxylate. In addition, ring-like conformers of another chain-type odorant, 2-methylpent-2-enal, were investigated to check the validity of the calculation method used.     

Novel nucleophilic C?C bond‐forming tele‐reaction of imidazole ring

Reaction of 2‐(1‐chloro‐2,2‐dimethylpropyl)‐1‐methyl‐1H‐irnidazoles with diethyl methylmalonate in the presence of NaH gave a normal S_N product, 2‐[(1,1‐diethoxycarbonylethyl)‐2,2‐dimethylpropyl]‐1‐methyl‐1H‐imidazole (2a) , and two tele‐reaction products, 5‐(1,1‐diethoxycarbonylethyl)‐1‐methyl‐2‐(2,2‐dimethylpropyl)‐1H‐imidazole (3a) and trans‐4,5‐di‐(1,1‐diethoxycarbonylethyl)‐4,5‐dihydro‐1‐methyl‐2‐(2,2‐dimethylpropyl)‐1H‐imidazole (4a) in 5, 17 and 70% yields, respectively. The scope and mechanism of this reaction are discussed.     

Recent trends of biosensors in Japan

Remarkable progress has been made in the development of bioelectrochemical sensors, and various kinds of biosensors have been developed and applied in analytical chemistry. Many of these enzyme, microbial, and immunosensors have been recently developed in Japan and in this paper, recent trends in Japanese biosensor development are described.