The gene cloning, purification, properties, kinetics, and antifungal activity of chitinase from marine Streptomyces sp. DA11 associated with South China sponge Craniella australiensis were investigated. Alignment analysis of the amino acid sequence deduced from the cloned conserved 451 bp DNA sequence shows the chitinase belongs to ChiC type with 80% similarity to chitinase C precursor from Streptomyces peucetius. Through purification by 80% ammonium sulfate, affinity binding to chitin and diethylaminoethyl-cellulose anion-exchange chromatography, 6.15-fold total purification with a specific activity of 2.95 Umg(-1) was achieved. Sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) showed a molecular weight of approximately 34 kDa and antifungal activities were observed against Aspergillus niger and Candida albicans. The optimal pH, temperature, and salinity for chitinase activity were 8.0, 50 degrees C, and 45 g per thousand psu, respectively, which may contribute to special application of this marine microbe-derived chitinase compared with terrestrial chitinases. The chitinase activity was increased by Mn(2+), Cu(2+), and Mg(2+), while strongly inhibited by Fe(2+) and Ba(2+). Meanwhile, SDS, ethyleneglycoltetraacetic acid, urea, and ethylenediaminetetraacetic acid were found to have significantly inhibitory effect on chitinase activity. With colloidal chitin as substrates instead of powder chitin, higher V (max) (0.82 mg product/min.mg protein) and lower K (m) (0.019 mg/ml) values were achieved. The sponge's microbial symbiont with chitinase activity may contribute to chitin degradation and antifungal defense. To our knowledge, it was the first time to study sponge-associated microbial chitinase.
A monolayer 1T′-WTe2 film is grown on SrTiO3(001) with in-plane tensile strain. A height of ∼0.7 nm, obvious charge transfer, and incommensurate charge fluctuations in 1T′-WTe2 suggest strong coupling to the STO substrate. Scanning tunneling spectroscopy on the surface reveals that a large energy gap opens at the Fermi level with nearly zero conductance. The opened energy gap decreases with the increase in the WTe2 island size. The lack of the metallic edge state on monolayer 1T′-WTe2/SrTiO3(001) indicates the absence of the quantum spin Hall (QSH) state. Our study here demonstrates that the energy gap of monolayer 1T′-WTe2 can be tuned by lattice strain and illustrates the importance of interface coupling to realize the metallic edge state and QSH in monolayer 1T′-WTe2.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.