Chemical Synthesis and Antigenicity Evaluation of an Aminoglycoside Trisaccharide Repeating Unit of Pseudomonas aeruginosa Serotype O5 O-Antigen Containing a Rare Dimeric-ManpN3NA.

Pseudomonas aeruginosa bacteria are becoming increasingly resistant against multiple antibiotics. Therefore, the development of vaccines to prevent infections with these bacteria is an urgent medical need. While the immunological activity of lipopolysaccharide O-antigens in P. aeruginosa is well-known, the specific protective epitopes remain unidentified. Herein, we present the first chemical synthesis of highly functionalized aminoglycoside trisaccharide 1 and its acetamido derivative 2 found in the P. aeruginosa serotype O5 O-antigen. The synthesis of the trisaccharide targets is based on balancing the reactivity of disaccharide acceptors and monosaccharide donors. Glycosylations were analyzed by quantifying the reactivity of the hydroxyl group of the disaccharide acceptor using the orbital-weighted Fukui function and dual descriptor. The stereoselective formation of 1,2-cis-α-fucosylamine linkages was achieved through a combination of remote acyl participation and reagent modulation. The simultaneous SN2 substitution of azide groups at C2' and C2″ enabled the efficient synthesis of 1,2-cis-ß-linkages for both 2,3-diamino-D-mannuronic acids. Through a strategic orthogonal modification, the five amino groups on target trisaccharide 1 were equipped with a rare acetamidino (Am) and four acetyl (Ac) groups. Glycan microarray analyses of sera from patients infected with P. aeruginosa indicated that trisaccharides 1 and 2 are key antigenic epitopes of the serotype O5 O-antigen. The acetamidino group is not an essential determinant of antibody binding. The ß-D-ManpNAc3NAcA residue is a key motif for the antigenicity of serotype O5 O-antigen. These findings serve as a foundation for the development of glycoconjugate vaccines targeting P. aeruginosa serotype O5.

Glycerol-driven adaptive evolution for the production of low-molecular-weight Welan gum: Characterization and activity evaluation.

Through adaptive laboratory evolution (ALE) of Sphingomonas sp. ATCC 31555, fermentation for production of low-molecular-weight welan gum (LMW-WG) was performed using glycerol as sole carbon source. During ALE, GPC-MALS analysis revealed a gradual decrease in WG molecular weight with the increase of adaptation cycles, accompanied by changes in solution conformation. LMW-WG was purified and structurally analyzed using GPC-MALS, monosaccharide composition analysis, infrared spectroscopy, NMR analysis, atomic force microscopy, and scanning electron microscopy. Subsequently, LMW-WG obtains hydration, transparency, antioxidant activity, and rheological properties. Finally, an in vitro simulation colon reactor was used to evaluate potential prebiotic properties of LMW-WG as dietary fiber. Compared with WG produced using sucrose as substrate, LMW-WG exhibited a fourfold reduction in molecular weight while maintaining moderate viscosity. Structurally, L-Rha nearly completely replaced L-Man. Furthermore, LMW-WG demonstrated excellent hydration, antioxidant activity, and high transparency. It also exhibited resistance to saliva and gastrointestinal digestion, showcasing a favorable colonization effect on Bifidobacterium, making it a promising symbiotic agent.

New Horizons in Probiotics: Unraveling the Potential of Edible Microbial Polysaccharides through In Vitro Digestion Models.

In vitro digestion models, as innovative assessment tools, possess advantages such as speed, high throughput, low cost, and high repeatability. They have been widely applied to the investigation of food digestion behavior and its potential impact on health. In recent years, research on edible polysaccharides in the field of intestinal health has been increasing. However, there is still a lack of systematic reviews on the application of microbial-derived edible polysaccharides in in vitro intestinal models. This review thoroughly discusses the limitations and challenges of static and dynamic in vitro digestion experiments, while providing an in-depth introduction to several typical in vitro digestion models. In light of this, we focus on the degradability of microbial polysaccharides and oligosaccharides, with a particular emphasis on edible microbial polysaccharides typically utilized in the food industry, such as xanthan gum and gellan gum, and their potential impacts on intestinal health. Through this review, a more comprehensive understanding of the latest developments in microbial polysaccharides, regarding probiotic delivery, immobilization, and probiotic potential, is expected, thus providing an expanded and deepened perspective for their application in functional foods.

Chemical Synthesis and Antigenicity Evaluation of Shigella dysenteriae Serotype 10 O-Antigen Tetrasaccharide Containing a (S)-4,6-O-Pyruvyl Ketal.

Shigella is the second most common etiologic pathogen responsible for childhood acute diarrhea. An anti-Shigella vaccine is still eagerly awaited due to the increasing drug resistance of this pathogen. The Shigella O-antigen is a promising vaccine target. To identify the immune epitopes of the glycan, the first total synthesis of Shigella dysenteriae serotype 10 O-antigen tetrasaccharide containing a (S)-4,6-O-pyruvyl ketal was completed. The 1,2-trans-ß-glycosylation & C2 epimerization and conformational locking strategies facilitated the construction of two 1,2-cis-ß-glycosidic linkages. The reactivities of both the glycosyl donor and acceptor were improved by adding electron-donating benzyl groups, enabling an efficient assembly of the tetrasaccharide. The (S)-4,6-O-pyruvyl ketal was introduced at the final stage due to its influence on the glycosylation stereospecificity and efficiency. In addition, (R)-4,6-O-pyruvylated and nonpyruvylated tetrasaccharides and three further fragments were synthesized. Glycan microarray screening revealed that the tetrasaccharide repeating unit is the key antigenic epitope of the O-antigen. Moreover, the (S)-4,6-O-pyruvyl ketal is an essential structural feature of this antigen for designing carbohydrate-based vaccines against S. dysenteriae serotype 10. The comparison of the (S)-4,6-O-pyruvylated glycan and its (R)-epimer will set an example for biological evaluation of other bacterial glycans containing pyruvyl ketals.

Novel application of multispectral refraction topography in the observation of myopic control effect by orthokeratology lens in adolescents.

BACKGROUND: Myopia, as one of the common ocular diseases, often occurs in adolescence. In addition to the harm from itself, it may also lead to serious complications. Thus, prevention and control of myopia are attracting more and more attention. Previous research revealed that single-focal glasses and orthokeratology lenses (OK lenses) played an important part in slowing down myopia and preventing high myopia. AIM: To compare the clinical effects of OK lenses and frame glasses against the increase of diopter in adolescent myopia and further explore the mechanism of the OK lens. METHODS: Changes in diopter and axial length were collected among 70 adolescent myopia patients (124 eyes) wearing OK lenses for 1 year (group A) and 59 adolescent myopia patients (113 eyes) wearing frame glasses (group B). Refractive states of their retina were inspected through multispectral refraction topography. The obtained hyperopic defocus was analyzed for the mechanism of OK lenses on slowing down the increase of myopic diopter by delaying the increase of ocular axis length and reducing the near hyperopia defocus. RESULTS: Teenagers in groups A and B were divided into low myopia (0D - -3.00 D) and moderate myopia (-3.25D - -6.00 D), without statistical differences among gender and age. After 1-year treatment, the increase of diopter and axis length and changes of retinal hyperopic defocus amount of group A were significantly less than those of group B. According to the multiple linear analysis, the retinal defocus in the upper, lower, nasal, and temporal directions had almost the same effect on the total defocus. The amount of peripheral retinal defocus (15°-53°) in group A was significantly lower than that in group B. CONCLUSION: Multispectral refraction topography is progressive and instructive in clinical prevention and control of myopia.

The role of Se content in improving anti-tumor activities and its potential mechanism for selenized Artemisia sphaerocephala polysaccharides.

Drawing an instructive point on the correlation between Se content and anti-tumor effects is helpful to develop Se-polysaccharides with potential anti-tumor activities. In this work, Se content-related anti-tumor activities are assessed in vitro by multiple comparisons among Na2SeO3, Artemisia sphaerocephala polysaccharide (ASP), and selenized ASP (SeASPs, Se contents 4344-13 030 µg g-1) synthesized by a chemical modification method. The results suggest that SeASPs exhibit potent anti-proliferation activities against three kinds of tumor cells by inducing apoptosis and cell cycle arrest, which is positively correlated to Se content. Meanwhile, SeASPs display low cytotoxicity against normal cells as compared with Na2SeO3 and 5-FU. A mitochondrial membrane potential assay and western blotting analysis suggest that the SeASPs induce HepG2 cell apoptosis via mitochondrial and death receptor pathways, which is confirmed by the reduced mitochondrial membrane potential, upregulated Bax/Bcl-2 ratio, promoted Cyt C release, and increased expression level of caspase-3/-9/-8. In an in vivo anti-tumor assay, SeASP with a high Se content (13 030 µg g-1) also obviously inhibits H22 tumor growth in a dose-dependent manner, and a tumor suppression rate of 45.10% is observed. In addition, the results of ELISA analysis suggest that SeASPs obviously increase the concentration of serum NO, cytokines (IL-1ß, IL-6, TNF-α), and Ig-G in a dose-dependent manner as compared with the control and ASP group. It could be concluded that adjusting the Se content might be an effective approach to improve the anti-tumor activities of Se-polysaccharides.

Acid site-regulated solid acids for polysaccharide Se-functionalization: Structural explanations for high reactivity.

In this work, the application of acid site-regulated solid acids in Se-functionalization of polysaccharide is evaluated for the first time, which aimed to further improve reaction efficiency and realize environmentally friendly chemistry. A series prepared MxOy/HZSM-5 catalysts possesses standard crystal structure, large specific surface area, pore volume, aperture as well as strong acidity. An efficient substitution of seleno-group on polysaccharide backbone is promoted by regulating the acid site of solid acids (Se content up to 15,170.49 µg/g) compared with the conventional Se-functionalization method (1703 µg/g). Strong Lewis and Brønsted acid sites lead to the driving forces toward low molecular mass polysaccharide fragments, but the deletion of main monosaccharide components is not observed. In summary, it is proved that solid acid can be employed in acid-dependent polysaccharide Se-functionalization which will promote useful in expanding our understanding of how to further develop polysaccharide resources.

Synthesis of Se-polysaccharide mediated by selenium oxychloride: Structure features and antiproliferative activity.

Selenium oxychloride (SOC) was employed as a highly reactive selenide reagent to synthesize selenized Artemisia sphaerocephala polysaccharides (SeASP). Se content of SeASP was significantly increased (∼22,400 µg/g) as compared to HNO3/H2SeO3 selenylation method (1703 µg/g). Furthermore, selenized ASP was prepared by using microwave-assisted synthesis which obviously enhanced selenylation kinetics. FT-IR, Raman, XPS and NMR results exhibited seleno-group was substituted at C6 position in the form of selenite (Se4+). SEC-MALLS suggested SOC system could effectively avoid the degradation of polysaccharide chain. Meanwhile, MALLS calculation, MB spectrophotometric method and AFM observation showed SeASP appeared spherical and rod-shaped conformation after selenylation. Seleno-groups were more likely to affect the conformational transformation of polysaccharide chains. Moreover, SeASP could significantly enhance antiproliferative activity against three tumor cells, of which the IC50 value of HepG2 was calculated as 24.35 µg/mL. It was found that higher Se content could effectively improve the antitumor activities of Se-polysaccharides in vitro.

A comparative study of sulfated tara gum: RSM optimization and structural characterization.

Interest in galactomannans and its derivatives as a functional health supplement is growing based on physicochemical properties. In this work, the optimized conditions of sulfated tara gum (STG) with a maximum DS of 0.66 by box-behnken design (BBD) were obtained as following: ratio of chlorosulfonic acid/pyridine 3:1, reaction time 4 h and reaction temperature 40 °C. The structure features of STG such as the degree of substitution (DS), substitution position, weight average molar mass (MW), monosaccharide components and chain conformation were investigated. Decreasing of MW, the increasing of Z-average radius of gyration (〈S2〉Z1/2) and specific volume for gyration (SVg) were obtained by SEC-MALLS. In addition, the structural properties of four sulfated galactomannans were comparatively investigated and analyzed based on our earlier reports of sulfated fenugreek gum, guar gum and locust bean gum. A conclusion was drown that higher galactose branch could enhance steric hindrance, which was inferred as one of the significant factors for the derivatization efficiency, thus affecting the DS, MW and conformational transition of sulfated galactomannans. This study will provide valuable information for further research on the comparison of bioactivities and medical application of galactomannans family.