Matrix metalloproteinase-2 inhibition and Zn2+-chelating activities of pyoverdine-type siderophores

Pyoverdine-type siderophores from fluorescent Pseudomonas species were purified by Zn2+-chelate chromatography, and their matrix metalloproteinase-2 (MMP-2) inhibition and metal-ion-chelating activities were studied. Structurally different pyoverdines showed different MMP-2 inhibition activities, and the inhibition activity was correlated with Zn2+-chelating activity. The IC50 value of a pyoverdine ((P113A1)-2, MW 1187) for MMP-2 was 0.27 microg/ml (0.23 microM).     

Genes and Gene Networks Involved in Sodium Fluoride-Elicited Cell Death Accompanying Endoplasmic Reticulum Stress in Oral Epithelial Cells

Here, to understand the molecular mechanisms underlying cell death induced by sodium fluoride (NaF), we analyzed gene expression patterns in rat oral epithelial ROE2 cells exposed to NaF using global-scale microarrays and bioinformatics tools. A relatively high concentration of NaF (2 mM) induced cell death concomitant with decreases in mitochondrial membrane potential, chromatin condensation and caspase-3 activation. Using 980 probe sets, we identified 432 up-regulated and 548 down-regulated genes, that were differentially expressed by >2.5-fold in the cells treated with 2 mM of NaF and categorized them into 4 groups by K-means clustering. Ingenuity^® pathway analysis revealed several gene networks from gene clusters. The gene networks Up-I and Up-II included many up-regulated genes that were mainly associated with the biological function of induction or prevention of cell death, respectively, such as Atf3, Ddit3 and Fos (for Up-I) and Atf4 and Hspa5 (for Up-II). Interestingly, knockdown of Ddit3 and Hspa5 significantly increased and decreased the number of viable cells, respectively. Moreover, several endoplasmic reticulum (ER) stress-related genes including, Ddit3, Atf4 and Hapa5, were observed in these gene networks. These findings will provide further insight into the molecular mechanisms of NaF-induced cell death accompanying ER stress in oral epithelial cells.     

Cloning and sequence analysis of poly(tetramethylene succinate) depolymerase from Acidovorax delafieldii strain BS-3

A gene encoding poly(tetramethylene succinate), PBS, depolymerase, pbsA, has been cloned from Acidovorax delafieldii strain BS-3 chromosomal DNA. The clone expressed in Escherichia coli showed the ability to degrade both PBS and poly[(tetramethylene succinate)-co-adipate] that are kinds of biodegradable plastics. PBS depolymerase was considered to be a kind of lipase, since it also degrades olive oil. It had no apparent hydrophobic-amino-acid-rich region which exists in other known plastic-degrading enzymes. From the result of amino acid homology search, PbsA was found to have some similarities with lipases of Streptomyces sp. and Mollaxella sp. In the motif surrounding the active site Ser residue (Gly-X1-Ser-X2-Gly), PbsA was revealed to have a Trp residue in the X1 position instead of His which is most likely found in other bacterial lipases.     

Experimental study on heat and fluid flow in LNG tank heated from the bottom and the sidewalls

Heat and fluid flow in a layer heated from the bottom and the sidewalls simulating an underground LNG tank is experimentally studied under high Rayleigh number (7.5×10¹⁰<Ra<1.5×10¹³) conditions by electrochemical mass transfer technique. The experiment yielded the following results. When sidewalls are heated, the heat transfer along the bottom surface is reduced. Heat transfer along sidewalls is independent of bottom heating, and is modeled by an equation for laminar natural convection flow even for Ra>10⁹. Convective flow pattern in the tank is visualized by the Schlieren technique. The results, combined with local mass transfer measurement, show that Sh of the bottom surface is reduced in the area where impinging downward flow exists. It is caused by the suppression of thermal plume formation by the downward flow. © 2004 Wiley Periodicals, Inc. Heat Trans Asian Res, 33(7): 417–430, 2004; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/htj.20031     

Room-temperature Coulomb staircase in semiconducting InP nanowires modulated with light illumination

Detailed electron transport analysis is performed for an ensemble of conical indium phosphide nanowires bridging two hydrogenated n(+)-silicon electrodes. The current-voltage (I-V) characteristics exhibit a Coulomb staircase in the dark with a period of ～ 1 V at room temperature. The staircase is found to disappear under light illumination. This observation can be explained by assuming the presence of a tiny Coulomb island, and its existence is possible due to the large surface depletion region created within contributing nanowires. Electrons tunnel in and out of the Coulomb island, resulting in the Coulomb staircase I-V. Applying light illumination raises the electron quasi-Fermi level and the tunneling barriers are buried, causing the Coulomb staircase to disappear.     

Improvement of carbon monoxide analysis in fish meat

Carbon monoxide (CO) treatment of fish meat of tuna, yellowtail, tilapia etc. is not allowed in Japan, since it can maintain the red color for a longer period than the microbiological shelf life of fish meat. The official method for quantification of CO has a problem, in that a part of the CO is lost during the preparation of the fish sample. To solve this problem, we modified the official method in this study. We also applied this modified method to survey the contents of CO in tuna, yellowtail, young yellowtail, and tilapia. As a result, the modified method was found to be more suitable for CO quantification than the official method. An inter-laboratory study by 4 laboratories confirmed that the CO content of many samples of tilapia exceeded the regulation value, apparently due to the higher recovery of CO, compared to the official method. Therefore, it was suggested that the regulation value in the case of tilapia should be changed if this method is introduced as an official method.     

Raman spectroscopy of indium phosphide nanowire networks coated with gold clusters

Enhanced Raman signal of the longitudinal optical phonon mode in indium phosphide nanowire networks with gold coating of up to 5 nm thickness was observed experimentally to further study the phonon spectrum of nanowire networks. Indium phosphide nanowire networks coated with different nominal thicknesses of gold were prepared and optically studied. Scanning electron microscopy, photoluminescence spectroscopy and Raman spectroscopy were used to study the dependence of surface morphology and phonon modes of the nanowire networks on the nominal thickness of the gold coating. The Raman peak of longitudinal optical phonon mode for as grown sample was negligible, while the peak intensity for 1 and 5 nm gold coated sample reached to 1,379 and 792 a.u. respectively. Electromagnetic enhancement and extinction coefficient are discussed to qualitatively assess the role of the gold coating on indium phosphide nanowire networks.     

Optoelectronic matrix switch using heterojunction switching photodiodes

Heterojunction switching photodiodes (InGaAs/InP) were used to construct a 3×3 matrix switch. Isolation and cross-talk losses were better than 63 dB over a frequency range of 10 Hz to 400 MHz and 400 Mbit/s digital signals were switched with switching times shorter than 30 ns.