A b s t r a c tThe pathogenic mechanism of neurodegenerative brain disorder such as Alzheimer's disease (AD)

Herein, a simple and novel electrochemical method for the detection of potassium ions (K(+)) was developed. In the presence of potassium ions, the potassium ions aptamer will form a G-quadruplex complex. Thus, further addition of hemin in the presence of potassium ions will lead to the formation of a recombined G-quadruplex. Then the electroactive label, hemin, will give an electrochemical response. The linear range of the method covered a large variation of K(+) concentration from 0.1 nM to 0.1 μ M and the detection limit of 0.1 nM was obtained. Moreover, this assay was able to detect K(+) with high selectivity and had great potential applications.

Tannases are a family of esterases that catalyze the hydrolysis of ester and depside bonds present in hydrolyzable tannins to release gallic acid. Here, a novel tannase from Lachnospiraceae bacterium (TanALb) was characterized. The recombinant TanALb exhibited maximal activity at pH 7.0 and 50°C, and it maintained more than 70% relative activity from 30°C to 55°C. The activity of TanALb was enhanced by Mg2+ and Ca2+, and was dramatically reduced by Cu2+ and Mn2+. TanALb is capable of degrading esters of phenolic acids with long-chain alcohols, such as lauryl gallate as well as tannic acid. The Km value and catalytic efficiency (kcat /Km) of TanALb toward five substrates showed that tannic acid (TA) was the favorite substrate. Homology modeling and structural analysis indicated that TanALb contains an insertion loop (residues 341–450). Based on the moleculer docking and molecular dynamics (MD) simulation, this loop was observed as a flap-like lid to interact with bulk substrates such as tannic acid. TanALb is a novel bacterial tannase, and the characteristics of this enzyme make it potentially interesting for industrial use.

β-galactosidase is a critical exoglycosidase involved in the hydrolysis of lactose, the modi cation and degradation of glycoprotein in vivo. In this study, the β-galactosidase gene of silkworm (BmGal), whose cDNA comprises 11 exons and contains an intact ORF of 1821bp, was cloned. The protein sequence of BmGal showed high similarity with other known insect β-galactosidases. No activity of the BmGal expressed in Escherichia coli or Pichia pastoris was detected while it was successfully expressed with high enzyme activity in baculovirus-silkworm expression system, and the electrophoresis result revealed that the BmGal showed activity in oligomer mode. Enzyme activity assay showed that its optimum pH was 8.4 and its optimum temperature was 40℃. What's more, we found that iron ions can stimulate the activity of the enzyme while cobalt, nickel or lead ions can inhibit its activity signi cantly. Besides, the temporal-spatial expression pattern of the BmGal mRNA level was analyzed, which showed that BmGal was expressed at the highest level in the fth larval instar but relatively low level in the pupal and adult stage, and the highest expression level of BmGal was found in testis among all the tissues concerned.