Journal of Carbohydrate Chemistry最新文献

To enhance our understanding of the activation and conjugation processes, reported herein is the synthesis of oligosaccharides comprising two sequential repeating units of capsular polysaccharide S. aureus serotype 8 (CP8). As in our previous syntheses of staphylococcal oligosaccharides, the potential propagation positions are blocked with methyl groups. While protein conjugates of carbohydrate antigens based on the structure of the S. aureus capsular serotypes have the potential to contribute to a S. aureus vaccine, despite promising preclinical data, efficacy has not been detected in human populations thus far.

An efficient and practical synthetic strategy, suitable for one-pot synthesis, for novel amide-linked oligosaccharide mimetics from sugar amino acid precursors is described. Twenty substrates, including twelve amide-linked disaccharide mimetics, four amide-linked trisaccharide mimetics and four amide-linked tetrasaccharide mimetics, were synthesized based on this strategy and its optimal conditions. This potentially general method is featured by high yields, gram-scale synthesis, wide substrate scope, and mild reaction conditions.

FeCl₃/C was used as an efficient and convenient promoter for glycosylation through Ferrier-type rearrangement of 3,4,6-tri-O-benzyl-D-glucal, which is a relatively unreactive substrate for this type of reaction. The method was applicable to a wide range of alcohols, especially phenols. A series of 2,3-unsaturated-O-glucosides were prepared efficiently (47–92%) by this method under mild conditions.

D-Glucuronyl C5-epimerase (C5-epi), which converts D-glucuronic acid to L-iduronic acid, is a crucial enzyme in the preparation of bioengineered heparin, which provides an alternative way to produce safer heparins. Herein, we provided an efficient way to measure the activity of cyanogen bromide-immobilized C5-epi based on proton nuclear magnetic resonance (NMR) analysis of perdeutero N-sulfoheparosan C5-epimerization. In this method, reactions catalyzed by C5-epi could be monitored by real-time 1 D NMR according to the peak intensity change of H-5 from IdoA and GlcA residues in the ¹H NMR spectrum, which is nondestructive of sample and also serves the kinetic property evaluation of immobilized C5-epi.

Carboxymethyl xylan (CMX) was synthesized and characterized. A method based on quantitative ¹³C NMR was developed to obtain detailed structural information. The total degree of substitution (DS), partial DS at 2- and 3-O-positions, and the quantitation of each unit in CMX could be acquired simultaneously by this method without decomposing the polymer backbone, thus avoiding errors caused by polymer hydrolysis with traditional methods using HPLC and ¹H NMR spectrometry. Moreover, different from methods of direct detection of carboxyl groups, such as acidometric and potentiometric titrations, this method was not affected by probable impurity introduced during carboxymethylation.

An engineered E. coli strain BL21 (DE3, SiaB, PmST3, △lacZ, △nanZ) that simultaneously encoded CMP-Neu5Ac synthase (SiaB) and α-2-3-sialyltransferase (PmST3) was constructed to synthesize GM3 trisaccharide. The crude E. coli lysate could be readily used for biosynthesis of GM3 trisaccharide with a nearly quantitative yield under optimal conditions. In addition, this engineered E. coli strain as whole-cell catalyst could generate approximately 1 g of GM3 trisaccharide in 40 mL of medium under optimal conditions. The whole-cell catalyst could be recycled and reused for at least 3 rounds without obvious loss of enzymatic activity.

The Pasteurella multocida hyaluronic acid synthase (pmHAS) is reported to be able to solve the problem of hyaluronic acid (HA) polydispersity, while simplifying its purification process. In the present study, we tried to design a mutant pmHAS enzyme with improved functional properties. In this regard, several mutations were predicted and exerted within the active site of the enzyme. The obtained results showed that the mutant enzyme was more stable and was able to bind to its ligands with higher affinity. Given our results, the mutated enzyme could be used to produce HA more efficiently and prevent the breakdown of HA.

Previously, our group constructed several immunogens utilizing oxime linkage to conjugate a T-cell stimulatory zwitterionic polysaccharide PS A1 and tumor associated carbohydrate antigens (TACAs) in acetate buffer. Here, a semi-synthetic immunogen was synthesized using hydrazone conjugation between PS A1 and a glycopeptide hydrazide (α-D-GalNAc-L-Thr-NH-NH₂) with an excellent loading in PBS buffer. To get robust immune response, the retention of zwitterionic character of PS A1 under vaccine construction conditions is essential. In this regard, the stability of embedded pyruvate acetal moiety in tetrasaccharide repeating unit of PS A1 can validate the retention of the dual charges. Therefore, rather than utilizing this highly immunogenic PS A1 fully, stability studies were performed with synthetic 1-thiophenyl-4,6-O-pyruvate acetal-D-galactopyranose in varying acetate buffer pHs and time intervals. Furthermore, 1-propyl-D-galactofuranose was synthesized to mimick the D-Galf of PS A1 to examine regioselective hydrazone and oxime formation with α-D-GalNAc-L-Thr-NH-NH₂ and α-D-GalNAc-ONH₂ moieties respectively.

Four polysaccharides, MFPA1, MFPA2, MFPB1, and MFPB2, were isolated from Mori Fructus using DEAE-52 cellulose chromatography. MFPA1 (177 kDa) was composed of mannose, rhamnose, glucose, and xylose, and MFPB1 (165 kDa) was composed of mannose, rhamnose, galacturonic acid, glucose, and xylose, while MFPA2 (638 kDa) and MFPB2 (380 kDa) were consisted of mannose, rhamnose, glucuronic acid, galacturonic acid, glucose, xylose, and arabinose. These polysaccharides were sulfated to obtained Four sulfated polysaccharides, S-MFPA1, S-MFPA2, S-MFPB1, and S-MFPB2. The characteristic absorptive bands of purified polysaccharides and sulfated polysaccharides were determined by FT-IR. MFPA1, MFPB1, S-MFPA1, and S-MFPB1 showed excellent activities to activate alcohol dehydrogenase in vitro. Subsequently, it was found that MFPA1 had the strongest antiacute alcoholic liver injury activity through the experiments with acute alcoholic liver injury in mice. These results provide important scientific basis for Mori fructus polysaccharides as a potential therapeutic agent against acute alcoholic liver injury.

The structures and chain conformations of two polysaccharides from Liriopes radix, WPRL-DS and UPRL-DS, isolated with hot water and ultrasound, respectively, were investigated by a combination of IR, GC, GC-MS, periodate oxidation, Smith degradation, NMR, AFM, and Congo red test. The results proved that the yield of ultrasonic extraction (UPRL-DS) was higher than that of hot water extraction (WPRL-DS). UPRL-DS had the same primary structure as WPRL-DS. However, UPRL-DS was spirally shaped whereas WPRL-DS was not. Both WPRL-DS and UPRL-DS were proved to have significant antioxidant activities as evidenced by their hydroxyl radical, superoxide anion, and 1,1-diphenyl-2-picryl-hydrazyl radical scavenging activities. UPRL-DS exhibited more effective antioxidant activity than WPRL-DS in a concentration-dependent manner.