Flow-injection determination of branched-chain L-amino acids with immobilized leucine dehydrogenase

L-Leucine, L-isoleucine and L-valine are determined by passage through a column of the enzyme immobilized on polystyrene beads, at pH 11.0. The NADH produced is monitored fluorimetrically. The detection limit is 0.1 nmol of L-leucine.     

Inkjet printed (bio)chemical sensing devices

Inkjet printing has evolved from an office printing application to become an important tool in industrial mass fabrication. In parallel, this technology is increasingly used in research laboratories around the world for the fabrication of entire (bio)chemical sensing devices or single functional elements of such devices. Regularly stated characteristics of inkjet printing making it attractive to replace an alternative material deposition method are low cost, simplicity, high resolution, speed, reproducibility, flexibility, non-contact, and low amount of waste generated. With this review, we give an overview over areas of (bio)chemical sensing device development profiting from inkjet printing applications. A variety of printable functional sensor elements are introduced by examples, and the advantages and challenges of the inkjet method are pointed out. It is demonstrated that inkjet printing is already a routine tool for the fabrication of some (bio)chemical sensing devices, but also that novel applications are being continuously developed. Finally, some inherent limitations of the method and challenges for the further exploitation of this technology are pointed out.     

Mechanism of the oscillating chemiluminescence reaction in the luminol-H2O2-KSCN-CuSO4-NaOH system

We conducted a simultaneous measurement of the potential of Cu²⁺, oxidation-reduction potential (ORP), and the chemiluminescence intensity in the luminol-H₂O₂-KSCN-CuSO₄-NaOH system. Two types of chemiluminescence were identified: a very faint continuous chemiluminescence and a strong oscillating chemiluminescence. The correlation between the potential of Cu²⁺ and ORP was measured experimentally for the first time. The effect of the initial concentrations of Cu²⁺ and H₂O₂ on the overall chemiluminescence intensity and the oscillation frequency was investigated in detail. Time-dependent concentration variation of the chemical species existing in the reaction system was calculated using a Runge-Kutta method. Two elementary chemical reactions not considered previously were taken into consideration. The overall experimental behavior was well explainable with our simulation. Based upon the comparison of our simulation with the experiment, we proposed that the strong oscillating chemiluminescence was induced by the reaction of luminol with ·OS(O)CN.     

Constitution of two coloring matters in the flower petals of CarthamusTinctorius L.

Structures of the safflower red pigment carthamin and the yellow pigment safflor yellow A are shown to be expressed by 3 and 4 respectively, mainly on the basis of spectroscopic evidence.     

Development of the new IC decapsulation technology

An IC is generally decapsulated with wet etching technology. The influences of environment and worker's health in usage and waste of the chemicals are seen as problems. Improvement of processing time is also needed. In order to overcome them, the laser processing technology is applied to IC decapsulation. In this paper, the relationship between processing condition and the processed surface quality is reported to select a suitable laser source. In addition, the new IC decapsulation technology, which is the combination of laser and wet etching, is proposed. To achieve the complex machining, firstly, the method of measuring the reflection light intensity of the laser is proposed to estimate the residual molding thickness. Secondly, the relationship between intensity of reflected laser and mold thickness to IC is shown to construct a mold thickness monitoring system. Finally, processing time and the volume of chemical solution used a process are compared with a conventional wet etching process.     

Boron cluster-based development of potent nonsecosteroidal vitamin D receptor ligands: direct observation of hydrophobic interaction between protein surface and carborane

We report here the design and synthesis of a novel vitamin D receptor (VDR) agonist whose hydrophobic core structure is p-carborane (1,12-dicarba-closo-dodecaborane, an icosahedral carbon-containing boron cluster having remarkable thermal and chemical stability and a characteristically hydrophobic B-H surface). This carborane-based VDR ligand exhibited moderate vitamin D activity, comparable to that of the natural hormone, despite its simple and flexible structure. X-ray structure analysis provided direct evidence that the carborane cage binds to the hydrophobic surface of the ligand-binding pocket of the receptor, promoting transition to the active conformation. These results indicate that the spherical B-H surface of carborane can function efficiently as a hydrophobic anchor in binding to the receptor surface, thereby allowing induced fitting of the three essential hydroxyl groups on the alkyl chains to the appropriate positions for interaction with the VDR binding site, despite the entropic disadvantage of the flexible structure. We suggest that carborane structure is a promising option in the design of novel drug candidates.     

Retention Behavior of Purine-Like Compounds on Titania and the Effect of Organic Modifiers Content in the Mobile Phase

The retention behavior of purine and purine-like compounds on titania was investigated in order to elucidate the strong retention of purine on titania. It was verified that, as expected, the strong retention stemmed from the formation of a chelate ring using the two nitrogen atoms N3 and N9 with titania. Purine has two possible tautometric forms because of proton tautomerism between N7 and N9. Hence, the lone pair of either of the two nitrogen atoms could be located immediately in an sp² orbital. Therefore, it was found that the lone pairs of N3 and N9 must be located in an sp² orbital, and the location is essential to forming the chelate with titania. Moreover, the effect of the presence of methanol and acetonitrile in the mobile phase on retention was also investigated. The retention strength increased with their content, but the tendency of this increase was different for the two organic solvents. It was concluded that the difference stems from the differing degrees of strength of the ligands, which includes the analytes and the solvents, as a result of competing with each other. Water and methanol acted as ligands strong enough to compete with the analytes, but acetonitrile did not, probably because it lacks hydroxy groups, which have a strong affinity for titania.     

Differences of fluorine in cements determined by photometric methods after distillation and pyrolysis.

Using a spectrophotometric method after distillation separation is a standard test method widely employed for the determination of fluorine (F) in cement. Using a flow injection (FI) method after pyrolysis separation for quantification of fluorine in cement has recently been developed. Differences between the fluorine content values obtained by each method have been noted. This paper documents the differences between fluorine content (distillation F) measured spectrophotometrically after distillation and that (pyrolysis F) determined using the FI method after pyrolysis for fourteen commercial Portland cements and identifies a factor contributing to the differences between distillation F and pyrolysis F values. A highly significant relationship existed between distillation F and pyrolysis F values for fourteen cements (r(2) = 0.998, p < 0.001).     

An improved synthesis of 3-(1-imidazolyl)-2-alkenoic acid derivatives and related compounds

The preparative method of 3-(1-imidazolyl)-2-alkenoic acid derivatives and the related compounds was improved by the use of strong bases such as sodium hydride in DMF. By this improved method, the preparation of 2-substituted 3-(1-imidazolyl)-2-alkenoic acid derivatives was accomplished in good yields.     

Determination of trace amounts of cobalt(II) by flow injection-solid phase spectrometry (FI-SPS) with 5-Br-PADAB.

Flow injection-solid phase spectrometry (FI-SPS) has been applied to the determination of cobalt(II) in water samples. The complex formed between cobalt and 5-Br-PADAB was on-line protonated and concentrated on an AG 50W-X2 cation-exchanger in a flow-through cell. The increase in absorbance caused by the accumulation of the complex in the resin was continuously measured. The interference by copper could be effectively eliminated by using EDDP as a masking agent. The detection limit was 40 ng dm(-3) with a 4.0 cm3 sample solution.