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Lianli Chi

Publications and source records attributed to Lianli Chi.

5 recordsLinked to original sources
PubMed2006

Quantitative continuous assay for hyaluronan synthase.

A rapid, continuous, and convenient three-enzyme coupled UV absorption assay was developed to quantitate the glucuronic acid and N-acetylglucosamine transferase activities of hyaluronan synthase from Pasteurella multocida (PmHAS). Activity was measured by coupling the UDP produced from the PmHAS-catalyzed transfer of UDP-GlcNAc and UDP-GlcUA to a hyaluronic acid tetrasaccharide primer with the oxidation of NADH. Using a fluorescently labeled primer, the products were characterized by gel electrophoresis. Our results show that a truncated soluble form of recombinant PmHAS (residues 1-703) can catalyze the glycosyl transfers in a time- and concentration-dependent manner. The assay can be used to determine kinetic parameters, inhibition constants, and mechanistic aspects of this enzyme. In addition, it can be used to quantify PmHAS during purification of the enzyme from culture media.

Fluorescent Dyes↗
PubMed2006

Electron detachment dissociation of glycosaminoglycan tetrasaccharides.

The first application of electron detachment dissociation (EDD) to carbohydrates is presented. The structural characterization of glycosaminoglycan (GAG) oligosaccharides by mass spectrometry is a longstanding problem because of the lability of these acidic, polysulfated carbohydrates. Doubly-charged negative ions of four GAG tetrasaccharides are examined by EDD, collisionally activated dissociation (CAD), and infrared multiphoton dissociation (IRMPD). EDD is found to produce information-rich mass spectra with both cross ring and glycosidic cleavage product ions. In contrast, most of the product ions produced by CAD and IRMPD result from glycosidic cleavage. EDD shows great potential as a tool for locating the sites of sulfation and other modifications in glycosaminoglycan oligosaccharides.

Electrons↗
PubMed2006

Preparation and structural determination of large oligosaccharides derived from acharan sulfate.

The structures of a series of large oligosaccharides derived from acharan sulfate were characterized. Acharan sulfate is an unusual glycosaminoglycan isolated from the giant African snail, Achatina fulica. Oligosaccharides from decasaccharide to hexadecasaccharide were enzymatically prepared using heparin lyase II and purified. Capillary electrophoresis and gel electrophoresis confirmed the purity of these oligosaccharides. Their structures, determined by ESI-MS and NMR, were consistent with the major repeating sequence in acharan sulfate, -->4)-alpha-d-GlcN(p)Ac-(1-->4)-alpha-l-IdoA(p)2S-(1-->, terminated by 4-linked alpha-d-GlcN(p)Ac residue at the reducing end and by 4,5-unsaturated pyranosyluronic acid 2-sulfate at the non-reducing end.

Animals↗
PubMed2003

Isolation and characterization of raw heparin from dromedary intestine: evaluation of a new source of pharmaceutical heparin.

Heparin, a heterogeneous anionic polysaccharide, is the glycosaminoglycan (GAG) used clinically an anticoagulant. This anticoagulant activity is primarily derived from its binding to the serine protease inhibitor antithrombin III, a potent inhibitor of thrombin (factor IIa) and factor Xa. Heparin is a complex natural product and its in vitro synthesis is not yet possible due to the difficulty of organizing the many biosynthetic enzymes required for its synthesis. The principle natural sources for heparin include porcine intestine and bovine lung. These two sources pose concerns for religious and health reasons, respectively. To circumvent these concerns, GAG from the intestinal tissue of one humped camel was isolated. Chemical characterization of this newly isolated GAG and spectroscopic analysis by 1D and 2D 1H-NMR were undertaken. Unsaturated disaccharide compositional analysis was performed on the enzymatically depolymerized GAG and the molecular weight of the isolated GAG was determined by gradient polyacrylamide gel electrophoresis. Anticoagulant activity of the newly isolated GAG was tested by using an anti-factor Xa assay. The results of these studies suggest that the GAG from one humped camel intestine is a mixture of heparin and heparan sulfate and represents an alternative source of heparin.

Animals↗