Abstract The DNA nuclease gene ST2109 has been cloned from the hyperthermophilic archaeon Sulfolobus tokodaii and expressed in Escherichia coli. The recombinant protein StoNurA has been purified to homogeneity by affinity chromatography and gel filtration chromatography. Biochemical analyses demonstrated that StoNurA exhibited DNA binding and 5’–3’ exonuclease activities towards ssDNA and dsDNA. The temperature and pH optima of StoNurA were determined to be 65 °C and 8.0, respectively. The activity of StoNurA was found to be dependent of Mn2+, and its half-life of heat inactivation at 100 °C was 5 min. Gel filtration chromatography revealed that StoNurA could form dimers in solution. Pull-down assays also showed that StoNurA physically interacted with a DNA helicase (StoHerA). Our data suggest that NurA may play a key functional role in the processing of DNA recombinational repair.

In order to comprehensively screen and identify the glycoside compounds in tobacco, a simple, rapid and sensitive method of high performance liquid chromatography/electrospray ionization linear ion-trap tandem mass spectrometry (HPLC-ESI-LIT/MSn) coupled with electrospray ionization orbitrap mass spectrometry (ESI-Orbitrap-MS) was developed for the first time. As a result, twenty-two glycoside compounds, including eleven alcoholic glycosides, eight phenolic glycosides, two ester glycosides and an indole glycoside, were reliably identified from tobacco with high mass accuracy (within 5 mDa). Among them, four compounds were confirmed as novel molecules and other four compounds, as far as we know, were not reported previously in tobacco. This study provided a useful tool to identify the new structures of glycoside compounds in natural products, especially when there were no reference compounds available.

ABSTRACT The effect on different three carbon source (i.e. glucose, fructose and sucrose) on production, chemical characterization and antioxidant activity of exopolysaccharide (EPS) produced by Phellinus vaninii Ljup was investigated in this study. Amongst carbon sources examined, glucose and sucrose were favorable for the mycelia growth, while the maximum EPS yield was achieved when sucrose was employed. The predominant carbohydrate compositions in EPSs identified were gluconic acid, glucose, mannose and galactose acid. Then, FT-IR spectral analysis revealed prominent characteristic groups in EPSs. EPSs molecule exist as nearly globular shape form in aqueous solution. The variation also affects antioxidant activities by investigated by using hydroxyl and DPPH radical scavenging assay. Sucrose was best carbon source from the viewpoint of antioxidant activity due to the relatively high contents of galactose in the EPS with moderate molecular weight and polydispersity.