Total Synthesis of the Repeating Units of Highly Functionalized O-Antigens of Pseudomonas aeruginosa ATCC 27577, O10, and O19.

The first total synthesis of the repeating units of the O-antigens of Pseudomonas aeruginosa ATCC 27577, O10, and O19 was achieved via a linear glycosylation strategy. This also represents the first synthesis of an oligosaccharide containing an α-linked N-acetyl-l-galactosaminuronic acid (l-GalpNAcA) unit. All of the glycosyl linkages, including three challenging 1,2-cis-glycosidic bonds of amino sugars, were effectively constructed with high to exclusive stereoselectivity, while orthogonal protection tactics were employed to facilitate regioselective glycosylations and the introduction of a variety of functionalities. An acetyl group migration phenomenon was found during the synthesis of the O-acylated repeating unit of the P. aeruginosa ATCC 27577 antigen. All synthetic targets carried an amino functional group in the linker at the reducing end, thus facilitating further regioselective elaboration and biological studies. The synthetic strategy established here should be useful for the preparation of other similar oligosaccharides.

Distribution characteristics of mercury concentration and estimation of mercury pools in different age groups of Larix gmelinii forests of Daxing'an Mountain.

Forests are important sinks of atmospheric mercury. Quantifying mercury pools in forest ecosystem tissues are essential for understanding the global mercury cycle. To reveal the characteristics of Hg concentration and Hg pool distribution in natural forests at different ages, samples from the vegetation layer, organic horizons, coarse wood debris, and mineral soil layers were collected in young forest, middle forest, near-mature forest, and mature forest of Larix gmelinii forests at the Daxing'an Mountain. The results showed that there were differences in the absorption and accumulation of Hg by different tree species and tissues. In Larix gmelinii, the concentration of Hg followed the order of bark > branch > leaf > root > core, whereas in Betula platyphylla, the order was bark > leaf > branch > root > core. The mercury concentration in the organic horizons increased gradually with the decomposition process. There were no obvious regular patterns in the mercury concentrations of each tissue in different age groups Larix gmelinii forests. Furthermore, total biomass mercury pools (overstory, shrub layer, herb layer, moss layer, and coarse woody debris （CWD）) in the young, middle, near-mature, and mature forests of Larix gmelinii forests at Daxing'an Mountain were estimated to be 99.0 µg m-2，207 µg m-2，207 µg m-2 and 194 µg m-2, respectively. On ecosystem scale, total mercury pools were 16.9 mg m-2 (young), 27.5 mg m-2 (middle), 17.0 mg m-2 (near-mature), and 11.8 mg m-2(mature). The mineral soil mercury pool accounts for 94.0%-98.1% of the total ecosystem mercury pool, and its mercury pool proportion gradually decreased with the increase in forest age. These obtained results are quite valuable for further assessing the role of forest ecosystems in the atmospheric mercury cycle and estimating potential mercury emissions from biomass burning during forest wildfires.

Surgical treatment of the lower cervical brucellosis with osteoporosis in the northwest region of China: review of 22 cases.

OBJECTIVE: To analyze the surgical treatment of patients with cervical brucellosis with osteoporosis over a 4-year period in Northwest China. METHODS: From 2013 to 2018, 22 patients (12 males and 10 females) with lower cervical spine brucellosis (C3-C7) underwent anterior lesion debridement, decompression, bone grafting and internal fixation combined with posterior bone graft fusion and internal fixation (ADDF+PIF). The follow-up period averaged 37.4 months (ranging from 24 to 57 months). RESULTS: Involvement of 1 vertebra was observed in 3 patients, involvement of 3 vertebrae was observed in 9 patients, and involvement of 3 vertebrae was observed in 10 patients. Before surgery, 1 patient had Frankel grade B, 2 had grade C, 9 had grade D, and 10 had grade E. In the final follow-up, 12 patients had neurological deficits, 10 patients improved by one grade, 6 patients improved by two grades, and the neurological status of 6 patients remained unchanged. In all cases, it was observed that bone fusion required 6.8 months on average. The kyphosis Cobb angle was enhanced from an average of 11.5° preoperatively (range 0°-24°) to 0.13° postoperatively (range 1°-5°), and there was no vital loss of correction in the follow-up. CONCLUSIONS: ADDF+PIF is an effective and safe treatment for patients with lower cervical brucellosis with osteoporosis.

Total Synthesis of the Tetrasaccharide Haptens of Vibrio vulnificus MO6-24 and BO62316 and Immunological Evaluation of Their Protein Conjugates.

Vibrio vulnificus is a human pathogen that can cause fatal septicemia and necrotizing infections with a high lethal rate exceeding 50%. V. vulnificus MO6-24 and BO62316 are two predominant virulent strains associated with approximately one-third of the clinical infections. The capsular polysaccharides (CPSs) of V. vulnificus consist of several structurally unique sugars and are excellent targets for developing effective glycoconjugate vaccines. This article describes the first total synthesis of the challenging tetrasaccharide repeating units of V. vulnificus MO6-24 and BO62316 CPSs. A key feature of this synthesis was the assembly of the tetrasaccharide skeleton using a 3,4-branched trisaccharide as the glycosyl donor. A modified TEMPO/BAIB oxidation protocol was developed to directly convert α-d-GalN into α-d-GalAN in not only disaccharides but also tri- and tetrasaccharides. The synthetic haptens were covalently coupled with CRM197 carrier protein via a bifunctional linker. Preliminary immunological studies of the resultant glycoconjugates in mice revealed their high efficacy to induce robust T-cell-dependent immune responses, and the IgG antibodies elicited by each glycoconjugate showed weak cross-reactivity with the other synthetic tetrasaccharide.

Stereoselective synthesis of a branched α-decaglucan.

The first and convergent synthesis of a branched Arca subcrenata Lischke α-decaglucan containing all of the α-(1 → 3), α-(1 → 4), and α-(1 → 6) glycosyl linkages was efficiently achieved. The tri- and tetrasaccharide fragments and fully protected decasaccharide were assembled in a one-pot manner with excellent α-stereoselectivity, which was secured by the synergistic α-directing effects of the TolSCl/AgOTf catalysis system and the remote participation effect or steric ß-shielding of functionalized groups at the donor 6-O-position. Low substrate concentration was revealed to favor the α-stereochemical outcome of glycosylations between bulkier building blocks. The synthetic approach established here would be very useful for the preparation of more complex α-glucans containing different types of glycosidic linkages and branched architectures.