Pattern of Specific Oxidation of Konjac Glucomannan with TEMPO/NaBr/NaClO system.

The TEMPO/NaBr/NaClO system was used to modify konjac glucomannan and prepare ß-1,4-linked D-mannuronic/glucuronic acid oligosaccharides. The impact of oxidant amount on the degree of oxidation, molecular weight, terminal structure and the ratio of sugar units were systematically investigated. Mannoses were transformed to mannuronic acids quantitatively, while some glucose were transformed to glucuronic acids, some degraded. The unspecific oxidation causes strong degradation of konjac glucomannan sugar chains. Multiple terminal structures were observed in the oxidized KGM products. According to those observations, the oxidation pattern of konjac glucomannan with the TEMPO/NaBr/NaClO system was speculated. It is suggested that the axial hydroxyl group at position 2 in mannose might form a hydrogen bond with the oxygen on the sugar ring. It would against the unspecific oxidation. While, both specific and unspecific oxidations were observed at glucose units with an equatorial hydroxyl group at position 2, and the degradation occurs mostly on glucose during the oxidation.

Preparation of 1,4-linked α-D-glucuronans from starch with 4-acetamide-TEMPO/NaClO2/NaClO system.

Oxidized starch (oxStarch) is a major derivative of starch. In present study, 4-acetamide-TEMPO system was firstly applied to prepare specifically oxidized starch, homogeneous 1,4-linked α-D-glucuronan. The impact of oxidant amount, 4-acetamide-TEMPO amount and reaction temperature on the properties of products were investigated. The product structures were characterized with 1H NMR for degree of oxidation (DO), SEC-MALS for MW, MS for analysis of oxidized oligosaccharides, and in-source fragmented MS for analysis of oxidized polysaccharides. The results showed that the DO of oxStarches increased, but their MWs decreased with the raise of oxidant amount; higher 4-acetamide-TEMPO amount provided higher efficiency of specific oxidation of starch, in which the product has higher DO and MW; no significant difference have been observed between the oxStarches oxidized at 4 and 25 °C, but significant degradation was observed at 50 °C. In each product, having a MW distribution, the portion with smaller size has higher DO. While some unspecific oxidation was still observed observed on the second hydroxyl groups of sugar ring in the following order of priority, position 3 > 2 > 1 > 0.

Structure characterization of a heavily fucosylated chondroitin sulfate from sea cucumber (H. leucospilota) with bottom-up strategies.

Two bottom-up strategies, disaccharide and oligosaccharide analyses, were applied to elucidate the structure of a fucosylated chondroitin sulfate (FCS). The FCS was hydrolyzed with mild acid. The remained part was digested with CS lyase for disaccharide analysis. The products from each step were analyzed and the results revealed that mild sulfuric acid mainly released sulfated fucose branches, but also affected some residues and sulfo-groups on the backbone. Over 140 oligosaccharide fragments were generated by catalytic oxidation and identified by HPSEC-MS, including sulfated fucose oligosaccharides exclusively from branches, sulfated backbone fragments, and junctional fragments. Based on the results provided by these two methods, the proposed backbone of the FCS is mainly composed of GlcA→GalNAc4S6S and GlcA→GalNAc6S, and the branch is mainly located at GalNAc. The longest branch observed is nonasaccharide, and most of the fucose on the branches are mono and/or di-sulfated. NMR results supported the conclusion.

Development of a method to analyze the complexes of enoxaparin and platelet factor 4 with size-exclusion chromatography.

Heparin, a highly sulfated glycosaminoglycan, has been used as a clinical anticoagulant over 80 years. However, heparin-induced thrombocytopenia and thrombosis (HITT) is a serious side effect of heparin therapy, resulting in relatively high risk of amputation and even death. HITT is caused by forming of complexes between heparin and platelet factor 4 (PF4). Enoxaparin, one of the most commonly used low molecular weight heparin (LMWH), were developed in 1980's. The lower molecular weight of enoxaparin reduces the risk of HITT by binding to less PF4. To detect the binding capacity between enoxaparin and PF4 could be an effect way to control this risk before it goes to patients. In this work, a size exclusion chromatography (SEC) method was developed to analyze the patterns of complexes formed between PF4 and enoxaparin. The chromatographic condition was optimized to separate PF4, enoxaparin, ultra-large complexes and small complexes. The linearity and stability of this method were confirmed. The impacts of PF4/enoxaparin mixture ratios and incubation time on the forming complexes were investigated. Four enoxaparin samples were analyzed with this method to verify its practicability. It is a robust, accurate and practicable method, and provides an easy way to monitor the capacity of enoxaparin forming complexes with PF4, suggesting the HITT related quality of enoxaparin.

Oxidation pattern of curdlan with TEMPO-mediated system.

In this study, the TEMPO-mediated (TEMPO/NaBr/NaClO) oxidation pattern of curdlan was investigated through comprehensively structural analysis of the corresponding oxidized products. During the structural analysis, infrared spectroscopy (IR), nuclear magnetic resonance (NMR) spectroscopy, gel permeation chromatography tandem multiple angle laser scattering (GPC-MALS) and ultra-high performance liquid chromatography tandem quadrupole time of flight mass spectrometry (UHPLC-Q/TOF-MS) were applied. As a result, the homogenous ß1-3 polyglucuronic acids (MW, 49.8, 29.8 and 7.0 kDa) were obtained with proper amount of oxidant (5.36 mmol NaClO) at various temperatures (4, 25, 50 °C), respectively. Compared to the oxidation of 1-4 linked glucan (starch and cellulose) with TEMPO-mediated system at same reaction conditions, higher degree of specific oxidation and less degradation were observed in that of 1-3 linked curdlan. The glycosylation at position 3 could stabilize the sugar ring, which inactivates the non-specific oxidation related hydroxyl groups on the sugar ring. Thus, the TEMPO-mediated system has higher selectivity to oxidize the primary hydroxyl groups of 1-3 linked curdlan and form polyglucuronic acid than those observed in the oxidation of starch and cellulose. In addition, same as those observed in previous work about starch, higher the temperature was used in the oxidation with TEMPO system, higher the activity of oxidant (NaClO solution) was, more non-specific oxidation occurred, and more the degradation were observed.