Flow-through micro sensor using immobilized peroxidase with chemiluminometric FIA system for determining hydrogen peroxide.

A micromachined flow cell (overall size; 25 x 25 x 1 mm3) was designed for the fast determination of hydrogen peroxide, based on a luminol-H2O2 chemiluminescence reaction catalyzed by immobilized peroxidase (POD). The flow cell consisted of a sandwich of anisotropically etched silicon and glass chips and contained a spiral channel (20 turns, 50 cm long, 150 microm wide, 20 microm depth, channel volume 1.4 microl) and two holes (1 mm diameter). POD was covalently immobilized with 3-(trimethoxysilyl)propyldietylenetriamine and glutaraldehyde on the inner surface of the channel. The chip was placed in front of a window of a photomultiplier tube and used as a flow cell in a single-line flow-injection analysis system using a luminol solution as a carrier solution. The sample volume for one measurement was 0.2 microl. The maximal sampling rate was 315 h(-1) at a carrier solution flow rate of 10 microl min(-1). A calibration graph for H2O2 was linear for 5 nM - 5 microM; the detection limit (signal-to-noise = 3) was 1 nM (7 fg in 0.2 microl injection). The H2O2 concentration in rainwater was determined using this sensor system.     

Tomato new sapogenols, isoesculeogenin A and esculeogenin B

Two novel sapogenols, isoesculeogenin A (1) and esculeogenin B (2) of steroidal alkaloid glycosides, lycoperoside F and esculeoside B, respectively, isolated from the ripe tomato have been characterized as (5alpha,22R,23R,25S)-3beta,23,27-trihydroxyspirosolane and (5alpha,22S,23R,25S)-22,26-epimino-16beta,23-epoxy-3beta,23,27-trihydroxycholestane, respectively.     

Isothiouronium-modified gold nanoparticles capable of colorimetric sensing of oxoanions in aqueous MeOH solution

Isothiouronium-modified gold nanoparticles 1 with an average diameter of 5.8 nm were synthesized from bis(5-(N,N′-dimethyl-S-isothiouronio)pentyl) disulfide 2. The surface plasmon band at 524 nm in 10% (v/v) H₂O-MeOH showed a selective red shift upon adding anions, making this potentially useful as a new anion sensor material.     

Daily variation in cellular content of UV-absorbing compounds mycosporine-like amino acids in the marine dinoflagellate Scrippsiella sweeneyae

Sudden exposure experiments to high PAR (photosynthetically available radiation) or high PAR+UVR (ultraviolet radiation) were conducted for the marine dinoflagellate Scrippsiella sweeneyae acclimated to either low PAR or high PAR to determine the induction of cellular mycosporine-like amino acid (MAA) in relation to photosynthesis status. When the exposure to high PAR (30.8 Wm(-2)) was provided at different time in the light period for S. sweeneyae acclimated to low PAR (7.7 Wm(-2)) which suppressed photosynthesis, S. sweeneyae could enhance the induction of MAA but it only occurred in the first half of the light period. When UVR exposure was provided for the culture acclimated to high PAR which enhanced photosynthesis, cellular MAA content did not increase during the entire light period, but displayed daily variation similar to the control for two and half days. Daily variation of cellular MAA content did not synchronized with that of cell volume and cellular chlorophyll a content. The individual MAAs also revealed similar daily variations with different phase, which increased for a few hours in the beginning of the light period, except for cellular palythine content. Thus the total cellular MAA content revealed daily variation with changing the relative composition within a few hours. As one of the biological protective strategies against harmful UVR in sunlight, the daily vertical migration in the bloom forming dinoflagellates might be accompanied by the daily variation of cellular MAA content for a photosynthesis at daytime.     

Effect of particle size of drug on conversion of crystals to an amorphous state in a solid dispersion with crospovidone

The effect of particle size on amorphization of drugs in a solid dispersion (SD) was investigated for two drugs, indomethacin (IM) and nifedipine (NP). The SD of drugs were prepared in a mixture with crospovidone by a variety of mechanical methods, and their properties investigated by particle sizing, thermal analysis, and powder X-ray diffraction. IM, which had an initial particle size of 1 μm and tends to aggregate, was forced through a sieve to break up the particles. NP, which had a large initial particle size, was jet-milled. In both cases, reduction of the particle size of the drugs enabled transition to an amorphous state below the melting point of the drug. The reduction in particle size is considered to enable increased contact between the crospovidone and drug particles, increasing interactions between the two compounds.     

Reduction‐Induced Highly Selective Uptake of Cesium Ions by an Ionic Crystal Based on Silicododecamolybdate

Cation adsorption and exchange has been an important topic in both basic and applied chemistry relevant to materials synthesis and chemical conversion, as well as purification and separation. Selective Cs⁺ uptake from aqueous solutions is especially important because Cs⁺ is expensive and is contained in radioactive wastes. However, the reported adsorbents incorporate Rb⁺ as well as Cs⁺, and an adsorbent with high selectivity toward Cs⁺ has not yet been reported. Highly selective uptake of Cs⁺ by an ionic crystal (etpyH)₂[Cr₃O(OOCH)₆(etpy)₃]₂[α‐SiMo₁₂O₄₀]?3 H₂O (etpy =4‐ethylpyridine) is described. The compound incorporated up to 3.8 mol(Cs⁺) mol(s)^?1 (where s=solid) by cation‐exchange with etpyH⁺ and reduction of silicododecamolybdate with ascorbic acid. The amount of Cs⁺ uptake was comparable to that of Prussian blue, which is widely recognized as a good Cs⁺ adsorbent. Moreover, other alkali‐metal and alkaline‐earth‐metal cations were almost completely excluded (<0.2 mol mol(s)^?1).