Factors affecting polyhydroxybutyrate biosynthesis in the marine photosynthetic bacteriumRhodopseudomonas sp. strain W-1S

Applied Biochemistry and Biotechnology - A marine photosynthetic bacterium,Rhodopseudomonas sp. strain W-1S, accumulated polyhydroxybutyrate (PHB) to 56% of the dry cell weight under microaerobic...     

Bioelectronic detector with monoamine oxidase for halitosis monitoring

Methyl mercaptan (MM) is known as one of the major chemicals of halitosis (bad breath). In this study, a bioelectronic gas sensor (bio-detector) for gaseous MM was developed and was applied to measure halitosis in breath. The bio-detector consisted of a Clark-type dissolved oxygen electrode, a monoamine oxidase type-A (MAO-A) immobilized membrane and a reaction unit that had liquid and gaseous compartments separated by a hydrophobic porous polytetrafluoroethylene (PTFE) diaphragm membrane. The tip of the electrode covered with MAO-A membrane was placed into the liquid compartment as touching to the PTFE diaphragm membrane. In order to amplify the bio-detector output, a substrate regeneration cycle caused by coupling the monooxygenase with l-ascorbic acid as reducing reaction with reagent system, was applied. The results of MM vapor measurements showed the calibration range of the bio-detector for MM vapor was from 0.087 to 11.5 ppm (correlation coefficient: 0.993) and included the human sense of smell level 5 (0.2 ppm). The bio-detector had good selectivity being attributed to enzyme specificity was obtained for several substances (trimethyl amine, ammonia, dimethyl sulfide, etc.). The bio-detector was applied for halitosis measurement. Expired gases in five subjects were sampled every hour and the concentrations of MM in the expired gases were monitored. The output of bio-detector showed behaviour of halitosis level changes in a day such as increasing with passage of time and decreasing after eating.     

A remarkable stereoselectivity switching upon solid-state versus solution-phase enantiodifferentiating photocyclodimerization of 2-anthracenecarboxylic acid mediated by native and 3,6-anhydro-γ-cyclodextrins

The enantiodifferentiating [4+4] photocyclodimerization of anthracenecarboxylic acid (AC) mediated by native, mono- and di-3,6-anhydro-γ-cyclodextrins was investigated in both aqueous solution and solid-state. The solid-state photolyses gave inherently disfavored head-to-head photodimers in much higher chemical and optical yields than in the aqueous solution.     

Importance of single electron-transfer in singlet oxygen reaction in aqueous solution : Oxidation of electron-rich thioanisoles

Oxidation of substituted thioanisoles by chemically generated singlet oxygen was investigated in polar aqueous media. The formation of the superoxide ion was observed during sulphoxidation of 4-hydroxythioanisole (4) in phosphate buffer at pH 7.5. Control experiments indicated that the superoxide ion was formed by a direct reaction between singlet oxygen and 4. The kinetics of the trapping reaction by diphenylsulphoxide indicated the involvement of a single intermediate. The overall rate constants of the reaction of thioanisoles with singlet oxygen in methanol-water (1:1) are one order of magnitude larger than those in benzene. On the basis of these results, a mechanism involving a charge-transfer complex has been proposed for the reaction of electron-rich thioanisoles with singlet oxygen, whereby the charge-transfer complex would produce persulphoxide directly or dissociate to the cation radical and superoxide ion in polar aqueous media.     

Determination of elemental composition of airborne dust and dust suspended in rain

To clarify the magnitude of wash-out effect of rain on the elemental composition of airborne dust and the possible origin of the dust, the dust samples were collected with a high-volume air sampler at the JAERI-Tokai. The dust suspended in rain was also collected from rain by filtration. Up to 20 elements in both types of the dust were determined by instrumental neutron activation analysis. It was found that the elements determined could be classified into 3 groups from the elemental composition and the elemental correlation in both types of the dust samples.