Unique fucosylated glycosaminoglycans (FG) have attracted increasing attention for various bioactivities. However, the precise structures of FGs usually vary in a species-specific manner. In this study, HfFG was isolated from Holothuria floridana and purified by anion exchange chromatography with the yield of ~0.9%. HfFG was composed of GlcA, GalNAc and Fuc, its molecular weight was 47.3 kDa, and the -OSO3−/-COO− molar ratio was 3.756. HfFG was depolymerized by a partial deacetylation–deaminative cleavage method to obtain the low-molecular-weight HfFG (dHfFG). Three oligosaccharide fragments (Fr-1, Fr-2, Fr-3) with different molecular weights were isolated from the dHfFG, and their structures were revealed by 1D and 2D NMR spectroscopy. HfFG should be composed of repeating trisaccharide units -{(L-FucS-α1,3-)d-GlcA-β1,3-d-GalNAc4S6S-β1,4-}-, in which sulfated fucose (FucS) includes Fuc2S4S, Fuc3S4S and Fuc4S residues linked to O-3 of GlcA in a ratio of 45:35:20. Furthermore, the heparanase inhibitory activities of native HfFG and oligosaccharide fragments (Fr-1, Fr-2, Fr-3) were evaluated. The native HfFG and its oligosaccharides exhibited heparanase inhibitory activities, and the activities increased with the increase of molecular weight. Additionally, structural characteristics such as sulfation patterns, the terminal structure of oligosaccharides and the presence of fucosyl branches may be important factors affecting heparanase inhibiting activity.
Earth's ionosphere disturbances triggered by the geomagnetic storm usually affect the propagation of radio electromagnetic wave. The mid-geomagnetic storm occurred in March 2013 with Dst index of up to -132 nT, which may disturb signal tracking and positioning results of Global Navigation Satellite Systems (GNSS). Unfortunately, LOS TEC series derived from GPS observations contain the ionospheric horizontal gradient information due to the satellites' movement. Geosynchronous Earth orbit (GEO) satellites of BeiDou navigation satellite system (BDS) give us an opportunity to detect ionospheric variations without horizontal gradient of electron density affection. In this paper, the Beidou stations' data provided by multi-GNSS experiments (MGEX) from IGS are the first time used to analyze the geomagnetic storm effects on Beidou navigation system (BDS) and ionospheric anomalous behaviors during 15-21 March 2013. The total electron content (TEC) variations are investigated during this geomagnetic storm using carrier phase measurements from BeiDou GEO satellites in B1 and B2. Dramatic TEC decrease is observed at the main storm and then increases gradually. Hourly TEC scintillation enhances greatly in the next hours of Storm Sudden Commencements (SSC). Although geomagnetic storm effect is global and regional, anomalies difference also can be detected by BDS-GEO TEC observations.
A fucan sulfate (HfFS) was isolated from the sea cucumber Holothuriafloridana after proteolysis-alkaline treatment and purified with anion-exchange chromatography. The molecular weight (Mw) of HfFS was determined to be 443.4 kDa, and the sulfate content of HfFS was 30.4%. The structural analysis of the peroxidative depolymerized product (dHfFS-1) showed that the primary structure of HfFS was mainly composed of a distinct pentasaccharide repeating unit -[l-Fuc2S4S-α(1,3)-l-Fuc-α(1,3)-Fuc-α(1,3)-l-Fuc2S-α(1,3)-l-Fuc2S-α(1,3)-]n-. Then, the “bottom-up” strategy was employed to confirm the structure of HfFS, and a series of fucooligosaccharides (disaccharides, trisaccharides, and tetrasaccharides) were purified from the mild acid-hydrolyzed HfFS. The structures identified through 1D/2D NMR spectra showed that these fucooligosaccharides could be derivates from the pentasaccharide units, while the irregular sulfate substituent also exists in the units. Anticoagulant activity assays of native HfFS and its depolymerized products (dHf-1~dHf-6) in vitro suggested that HfFS exhibits potent APTT-prolonging activity and the potencies decreased with the reduction in molecular weights, and HfFS fragments (dHf-4~dHf-6) with Mw less than 11.5 kDa showed no significant anticoagulant effect. Overall, our study enriched the knowledge about the structural diversity of FSs in different sea cucumber species and their biological activities.
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.