For the production of oligosaccharides from chitosan, a chitosanase-producing bacterium, S65, was isolated from soil. On the basis of phylogenetic analysis of the 16S rDNA gene sequence and phenotypic analysis, S65 was identified as a Bacillus sp. strain. This bacterium constitutively produced chitosanase in a culture medium without chitosan as an inducer. S65 chitosanase was homogeneously purified by DEAE Sepharose fast flow anion exchange followed by Superdex 75 size exclusion, and the molecular weight was 45 kDa according to SDS−PAGE. Enzyme analysis showed that the optimum pH and temperature of S65 were 6.0 and 65 °C, respectively. Catalytic activity was stable from pH 5.5−6.5 at temperatures below 40 °C, and the pI of chitosanase was about 6.0 as determined by a test tube method. S65 chitosanase degraded carboxymethyl cellulose (CMC) at the degree of about 5.3% relative to the value of soluble chitosan, but it cannot hydrolyze colloidal chitin and crystalline cellulose. Gene encoding was cloned and sequenced. The deduced amino acid sequence of the S65 exhibited the highest homology to those of family 8 glycanase, suggesting that the enzyme belonged to family 8. Keywords: Chitosan; chitosanase; purification; characterization; gene cloning

We present two approaches for studying the uniformity of a tunnel barrier. The first approach is based on measuring single-electron and two-electron tunneling in a hybrid single-electron transistor. Our measurements indicate that the effective area of a conduction channel is about one order of magnitude larger than predicted by theoretical calculations. With the second method, transmission electron microscopy, we demonstrate that variations in the barrier thickness are a plausible explanation for the larger effective area and an enhancement of higher order tunneling processes.

ABSTRACT

A black‐brown powder was synthesized from melamine (C3N6H6) at 850 °C and 4.5 GPa. There are two possibilities for the sample phase components based on the analyses of C/N/H elements and X‐ray diffraction patterns. One is that the powder is composed of 2H‐type g‐C3N4 and some intermediate phases, while the other is that it consists of some undecomposed raw material, graphite and intermediate phases. The existence of the intermediate phase with long periodicity along one direction is confirmed through transmission electron microscopy observations. Scanning electron microscopy images show many block regions, in which a few holes exist. The atomic fraction of carbon and nitrogen was checked with energy dispersive X‐ray analysis, and the chemical bond states were investigated by Fourier transform infrared spectroscopy and X‐ray photoelectron spectroscopy. Based on the general analysis of the experimental results, the second possibility is favoured. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)