Analysis of Structure and Antioxidant Activity of Polysaccharides from Aralia continentalis.

We extracted, purified, and characterized three neutral and three acidic polysaccharides from the roots, stems, and leaves of Aralia continentalis Kitigawa. The results of the analysis of monosaccharide composition indicated that the polysaccharides from the roots and stems were more similar to each other than they were to the polysaccharides from the leaves. The in vitro antioxidant results demonstrated that the acidic polysaccharides had stronger antioxidant activity than the neutral fractions. Therefore, we investigated the primary purified acidic polysaccharide fractions (WACP(R)-A-c, WACP(S)-A-c, and WACP(L)-A-d) by NMR and enzymatic analysis. The structural analytical results indicated that WACP(R)-A-c contained homogalacturonan (HG); WACP(S)-A-c contained HG and rhamnogalacturonan II (RG-II), and WACP(L)-A-d contained HG, RG-II, and rhamnogalacturonan I (RG-I) domains. Our findings offer insights into the screening of natural polysaccharide-based antioxidants and provide a theoretical basis for the application of A. continentalis.

Study on the Biochemical Characterization and Selectivity of Three ß-Glucosidases From Bifidobacterium adolescentis ATCC15703.

Three ß-glucosidases from Bifidobacterium adolescentis ATCC15703, namely, BaBgl1A, BaBgl3A, and BaBgl3B, were overexpressed in Escherichia coli. The recombinant ß-glucosidases were sufficiently purified using Ni2+ affinity chromatography, and BaBgl1A exhibited the best purification efficiency with a purification factor of 2.3-fold and specific activity of 71.2 U/mg. Three recombinant ß-glucosidases acted on p-nitrophenyl-ß-glucopyranoside (pNPßGlc) at around pH 7.0 and 30-50°C. The results of the substrate specificity assay suggested that BaBgl1A acted exclusively as ß-1,2-glucosidase, while BaBgl3A and BaBgl3B acted mostly as ß-1,3-glucosidase and ß-1,4-glucosidase, respectively. The substrate specificity of the three recombinant enzymes was further studied using the ginsenosides Rb1 and Rd as substrates. The results of thin-layer chromatography and high-performance liquid chromatography analyses showed that BaBgl1A exhibited the highest bioconversion ability on Rb1 and Rd, where it hydrolyzed the outer C-3 glucose moieties of Rb1 and Rd into the rare ginsenosides Gypenoside XVII and F2; BaBgl3A exhibited medium bioconversion ability on Rb1, where it hydrolyzed both the outer C-3 and C-20 glucose moieties of Rb1 into Gyp XVII and Rd; and BaBgl3B was not active on Rb1 and Rd. These ß-glucosidases will act as new biocatalytic tools for transforming ginsenosides and preparing active glycosides and aglycone.

Study on skylight polarization patterns over the ocean for polarized light navigation application.

Polarized skylight navigation has excellent navigation performance with no error accumulation over time and low susceptibility to interference. The skylight polarization distribution contains rich directional information, such as the solar meridian, the neutral point, and the polarization angle, which plays a key role in the polarization navigation. But up to now the polarizations of both sunlit and moonlit skies have been investigated mainly over the land. In this work, the polarization distribution patterns of the skylight over the East China Sea and the Yellow Sea were studied. The polarization patterns were captured continuously during daytime and nighttime by using a full-sky imaging polarimetry system and then compared with the simulation results using the libRadtran radiative transfer software package. The result shows that the skylight polarization distribution over the sea has almost the same pattern as that on the land. The accuracy of the angle of polarization and the degree of polarization dropped significantly under the cloudy sky. It was found that when the ship sailed on the sea, the direction of the real meridian was close to the solar azimuth during the daytime and close to the lunar azimuth during the nighttime. It was also found that the nautical twilight polarization distribution was affected by both the solar polarization and the lunar polarization, but the solar polarization was dominant. The experiments show that the skylight polarization distribution pattern over the sea can still be applied in the field of polarization navigation. Thus, it is feasible for ships and unmanned aerial vehicles to use the polarized skylight to navigate and orient on the sea.