Liquid-state NMR spectroscopy for complex carbohydrate structural analysis: A hitchhiker's guide

Impact of glycosylation on viral vaccines

Glycosylation is the most prominent modification important for vaccines and its specific pattern depends on several factors that need to be considered when developing a new biopharmaceutical. Tailor-made glycosylation can be exploited to develop more effective and safer vaccines; for this reason, a deep understanding of both glycoengineering strategies and glycans structures and functions is required. In this review we discuss the recent advances concerning glycoprotein expression systems and the explanation of glycans immunomodulation mechanisms. Furthermore, we highlight how glycans tune the immunological properties among different vaccines platforms (whole virus, recombinant protein, nucleic acid), also comparing commercially available formulations and describing the state-of-the-art analytical technologies for glycosylation analysis. The whole review stresses the aspect of glycoprotein glycans as a potential tool to overcome nowadays medical needs in vaccine field.

Structure and in vitro antiproliferative activity against breast cancer cells of the cell-wall polysaccharide from the marine bacterium Kangiella japonica KMM 3899T

Kangiella japonica KMM 3899T is a Gram-negative bacterium isolated from a sandy sediment sample collected from the Sea of Japan. Here the results of the structure and the biological activity against breast cancer cells of the cell-wall polysaccharide from K. japonica KMM 3899T have been described. The structure of the repeating unit of the polysaccharide was elucidated using chemical analysis and NMR spectroscopy: →4)-α-L-GalpNAc3AcA-(1 → 3)-α-D-GlcpNAc-(1 → 4)-β-D-GlcpNAc3NAcAN-(1→. The cell-wall polysaccharide had an antiproliferative effect against T-47D cells. Flow cytometric and Western blot analysis revealed that the polysaccharide induced S phase arrest and mitochondrial-dependent apoptosis.

Exploring the anti-migraine effects of Tianshu capsule: chemical profile, metabolic behavior, and therapeutic mechanisms

BACKGROUND

Migraine is widely recognized as the third most prevalent medical condition globally. Tianshu capsule (TSC), derived from "Da Chuan Xiong Fang" of the Jin dynasty, is integral in the clinical treatment of migraine. However, the chemical properties and therapeutic mechanisms of TSC different portions remain unclear.

PURPOSE

This study was designed to investigate the effects of TSC different portions (including small molecular TSCP-SM and polysaccharides TSC-P) on migraine and explore the underlying mechanisms.

STUDY DESIGN AND METHODS

First of all, migraine rats were established by nitroglycerin injection and treated with TSC, TSC-P, and TSC-SM. ELISA, qPCR, and immunofluorescence were used to evaluate the pharmacological effects on migraine rats. Secondly, UPLC-Q/TOF-MS and GC--MS were employed to detect the components of TSC-SM. PMP-HPLC, NMR, FT-IR, UV-Vis, AFM, and SEM were used for the chemical profiling of polysaccharides. Thirdly, the metabolic behavior profile of TSC-P was characterized by oral administrated fluorescence-labeled TSC-P and detected by NIRF imaging. Finally, the anti-migraine mechanisms were explored by determining the composition of gut microbiota, analyzing colonic short-chain fatty acids (SCFAs), and examining serum tryptophan-related metabolites.

RESULTS

Both small molecules (45 volatiles and 114 small molecules) and polysaccharides (including Glc, Ara, Gal, and Gal A) have exhibited effectiveness in alleviating migraine, and this efficacy is associated with reduced CGRP and iNOS levels, along with increased β-EP expressions. Further mechanistic exploration revealed that small-molecules exhibited effectiveness in migraine treatment by exerting antioxidative actions, while polysaccharides demonstrated superior therapeutic effects in regulating 5-HT levels. By monitoring the metabolic behavior of polysaccharides with fluorescent labeling, it was observed that TSC-P exhibited poor absorption. Instead, TSC-P demonstrated its therapeutic effects by modulating the aberrations in gut microbiota (including Alloprevotella, Muribaculaceae_ge, and Ruminococcaceae_UCG-005), cecum short-chain fatty acids (such as isobutyric, isovaleric, and valeric acids), and serum tryptophan-related metabolites (including indole-3-acetamide, tryptophol, and indole-3-propionic acid).

CONCLUSION

This research provides innovative insights into chemical composition, metabolic behavior, and proposed anti-migraine mechanisms of TSC from a polarity-based perspective, and pioneering an exploration focused on the polysaccharide components within TSC for the first time.

An arabinoxylan (AOP70-1) isolated from Alpinia oxyphylla alleviates neuroinflammation and neurotoxicity by TLR4/MyD88/NF-κB pathway

Alpinia oxyphylla is famous for its neuroprotective and memory-improving effects. A crude polysaccharide AO70 from A. oxyphylla remarkably ameliorated neuroinflammation and cognitive dysfunction in Alzheimer's disease mice. This study aimed to explore the bioactive component of AO70 and its mechanism of action. A homogeneous polysaccharide (AOP70-1) rich in arabinose and xylose was purified from AO70, which was consisted of α-L-Araf-(1→, →5)-α-L-Araf-(1→, β-D-Xylp-(1→,→2,4)-β-D-Xylp-(1→, →2,3,4)-β-D-Xylp-(1→, α-L-Rhap-(1→, α-D-Manp-(1→, →4)-α-D-Glcp-(1→, →4)-α-D-GlcpA-(1→, β-D-Galp-(1→, →2)-α-D-Galp-(1→, →6)-α-D-Galp-(1 → and →3,6)-α-D-Manp-(1→. AOP70-1 (2.5, 5, 10 μM) significantly suppressed NO, IL-1β, and TNF-α production in a concentration-dependent manner and inhibited the migration of BV2 microglia to normal levels. AOP70-1 inhibited LPS-mediated activation of Toll-like receptor 4 (TLR4), myeloid differentiation primary response protein (MyD88), and nuclear factor kappa B (NF-κB). Moreover, AOP70-1 exerted neuroprotection on SH-SY5Y cells and primary neurons by reducing neuronal apoptosis (72 %, 44 %), alleviating ROS accumulation (63 %, 55 %), and improving mitochondrial membrane potential (63 %, 77 %). Overall, AOP70-1 is one of the major bioactive components in AO70 from A. oxyphylla, which has great potential in the prevention and treatment of neuroinflammation.

Structural characterization of a galactoglucomannan with anti-neuroinflammatory activity from Ganoderma lucidum

According to traditional Chinese medicine theory, Ganoderma lucidum (G. lucidum) presents certain effects for nourishing nerves and calming the mind. G. lucidum polysaccharides (GLPs) have various biological activities; however, the structural characterization and the structure-activity relationship in anti-neuroinflammation of GLPs needs to be further investigated. In this work, the crude polysaccharide GL70 exhibited a remarkable impact on enhancing the spatial learning and memory function, as well as reducing the anxiety symptoms of the lipopolysaccharide (LPS)-induced rat model of Alzheimer's disease (AD). A galactoglucomannan (GLP70-1-2) was isolated from GL70, and characterized by monosaccharide composition, partial acid hydrolysis, methylation, and NMR analysis. The backbone of GLP70-1-2 was →6)-α-D-glcp-(1 → 6)-β-D-galp-(1 → [6)-β-D-manp-(1]3 → 4)-α-D-Glcp-(1 → 6)-α-D-glcp-(1 → 2)-β-D-galp-(1 → [4)-α-D-glcp-(1 → 6)-β-D-manp-(1 → 2)-β-D-galp-(1]2 → 6)-β-D-glcp-(1 → 6)-β-D-glcp-(1→ with two side chains attached to O-4 of →6)-β-D-galp-(1→ and O-3 of →6)-β-D-glcp-(1→, respectively. In addition, GLP70-1-2 exhibited remarkable efficacy in decreasing the level of pro-inflammatory factors in LPS-activated BV2 cells through the TLR4/MyD88/NF-κB pathway. Collectively, GLP70-1-2 exhibited significant anti-neuroinflammatory activity and may have the potential for developing as a drug for AD.

Structural elucidation and immunomodulatory activities in vitro of type I and II arabinogalactans from different origins of Astragalus membranaceus

Astragalus membranaceus polysaccharide (APS) possesses excellent immunomodulatory activity. However, there are several studies on the structural characterization of APS. Here, we aimed to elucidate the repeating units of polysaccharides (APS1, 106.5 kDa; APS2, 114.5 kDa) obtained from different Astragalus membranaceus origins and further investigated their immunomodulatory activities. Based on structural analysis, types of the two polysaccharides were identified as arabinogalactan-I (AG-I) and arabinogalactan-II (AG-II), and co-elution of arabinogalactans (AGs) and α-glucan was observed. The backbone of AG-I was 1,4-linked β-Galp occasionally substituted by α-Araf at O-2 and/or O-3. AG-II was a highly branched polysaccharide with long branches of α-Araf, which were attached to the O-3 of 1,6-linked β-Galp of the backbone. The presence of AGs in A. membranaceus was confirmed for the first time. The two polysaccharides could promote the expression of IL-6, IL-1β and TNF-α in RAW264.7 cells via MAPKs and NF-κB signaling pathways. The constants for APS1 and APS2 binding to Toll-like receptor 4 (TLR4) were 1.83 × 10-5 and 2.08 × 10-6, respectively. Notably, APS2 showed better immunomodulatory activity than APS1, possibly because APS2 contained more AGs. Hence, the results suggested that AGs were the vital components of APS in the immunomodulatory effect.

Structural clarification of mannoglucan GSBP-2 from Ganoderma sinense and its effects on triple-negative breast cancer migration and invasion

Ganoderma sinense, known as Lingzhi in China, is a medicinal fungus with anti-tumor properties. Herein, crude polysaccharides (GSB) extracted from G. sinense fruiting bodies were used to selectively inhibit triple-negative breast cancer (TNBC) cells. GSBP-2 was purified from GSB, with a molecular weight of 11.5 kDa and a composition of α-l-Fucp-(1→, β-d-Glcp-(1→, β-d-GlcpA-(1→, →3)-β-d-Glcp-(1→, →3)-β-d-GlcpA-(1→, →4)-α-d-Galp-(1→,→6)-β-d-Manp-(1→, and →3,6)-β-d-Glcp-(1→ at a ratio of 1.0:6.3:1.7:5.5:1.5:4.3:8.0:7.9. The anti-MDA-MB-231 cell activity of GSBP-2 was determined by methyl thiazolyl tetrazolium, colony formation, scratch wound healing, and transwell migration assays. The results showed that GSBP-2 could selectively inhibit the proliferation, migration, and invasion of MDA-MB-231 cells through the regulation of genes targeting epithelial-mesenchymal transition (i.e., Snail1, ZEB1, VIM, CDH1, CDH2, and MMP9) in the MDA-MB-231 cells. Furthermore, Western blotting results indicated that GSBP-2 could restrict epithelial-mesenchymal transition by increasing E-cadherin and decreasing N-cadherin expression through the PI3K/Akt pathway. GSBP-2 also suppressed the angiogenesis of human umbilical vein endothelial cells. In conclusion, GSBP-2 could inhibit the proliferation, migration, and invasion of MDA-MB-231 cells and showed significant anti-angiogenic ability. These findings indicate that GSBP-2 is a promising therapeutic adjuvant for TNBC.

The structures of two polysaccharides from Lepidium meyenii and their immunomodulatory effects via activating NF-κB signaling pathway

Lepidium meyenii Walp., also known as the "Peruvian national treasure", is a popular functional food in the daily lives of Peruvian people due to its bioactive with main polysaccharides. However, studies on polysaccharides isolated from Lepidium meyenii were few. Two new highly heterogeneous polysaccharides, MCP-1a and MCP-2b, were isolated and purified from the tuber of Lepidium meyenii. The structure characterization revealed that MCP-1a primarily consisted of D-Glc and had a molecular weight of 6.6 kDa. Its backbone was composed of 1,4,6-α-D-Glc, while branches feature T-α-L-Ara, 1,5-α-L-Ara, and T-α-D-Glc attached to the O-6 positions. MCP-2b was a rare arabinogalactan with a molecular weight of 49.4 kDa. Interestingly, the backbone of MCP-2b was composed of 1,6-β-D-Gal, 1,3,6-β-D-Gal with a few 1,3-β-D-GlcpA-4-OMe units inserted. Side chains of MCP-2b were mainly composed of 1,3-β-D-Gal, T-β-D-Gal, T-α-L-Ara, 1,5-α-L-Ara, with trace amounts of 1,4-β-D-Glc and T-β-D-Glc. The bioactivity assay results revealed that MCP-1a and MCP-2b increased the release of NO, IL-1β, TNF-α, and IL-6 from RAW 264.7 cells at concentrations ranging from 50 μg/mL to 400 μg/mL. Furthermore, MCP-1a and MCP-2b could promote the expression of key transcription factors (IκB-α, p-IκB-α, p65, and p-p65) in the NF-κB pathway, indicating that MCP-1a and MCP-2b had potential immunomodulatory activities.

A glucuronogalactomannan isolated from Tetrastigma hemsleyanum Diels et Gilg: Structure and immunomodulatory activity

A novel acidic glucuronogalactomannan (STHP-5) was isolated from the aboveground part of Tetrastigma hemsleyanum Diels et Gilg with a molecular weight of 3.225 × 105 kDa. Analysis of chain conformation showed STHP-5 was approximately a random coil chain. STHP-5 was composed mainly of galactose, mannose, and glucuronic acid. Linkages of glycosides were measured via methylation analysis and verified by NMR. In vitro, STHP-5 induced the production of nitric oxide (NO) and secretion of IL-6, MCP-1, and TNF-α in RAW264.7 cells, indicating STHP-5 had stimulatory activity on macrophages. STHP-5 was proven to function as a TLR4 agonist by inducing the secretion of secreted embryonic alkaline phosphatase (SEAP) in HEK-Blue™-hTLR4 cells. The TLR4 activation capacity was quantitatively measured via EC50, and it showed purified polysaccharides had stronger effects (lower EC50) on activating TLR4 compared with crude polysaccharides. In conclusion, our findings suggest STHP-5 may be a novel immunomodulator.

Genomic and functional evaluation of exopolysaccharide produced by Liquorilactobacillus mali t6-52: technological implications

BACKGROUND

This study explores the biosynthesis, characteristics, and functional properties of exopolysaccharide produced by the strain Liquorilactobacillus mali T6-52. The strain demonstrated significant EPS production with a non-ropy phenotype.

RESULTS

The genomic analysis unveiled genes associated with EPS biosynthesis, shedding light on the mechanism behind EPS production. These genes suggest a robust EPS production mechanism, providing insights into the strain's adaptability and ecological niche. Chemical composition analysis identified the EPS as a homopolysaccharide primarily composed of glucose, confirming its dextran nature. Furthermore, it demonstrated notable functional properties, including antioxidant activity, fat absorption capacity, and emulsifying activity. Moreover, the EPS displayed promising cryoprotective activities, showing notable performance comparable to standard cryoprotective agents. The EPS concentration also demonstrated significant freeze-drying protective effects, presenting it as a potential alternative cryoprotectant for bacterial storage.

CONCLUSIONS

The functional properties of L. mali T6-52 EPS reveal promising opportunities across various industrial domains. The strain's safety profile, antioxidant prowess, and exceptional cryoprotective and freeze-drying characteristics position it as an asset in food processing and pharmaceuticals.

Nanopore-based glycan sequencing: state of the art and future prospects

Sequencing of biomacromolecules is a crucial cornerstone in life sciences. Glycans, one of the fundamental biomolecules, derive their physiological and pathological functions from their structures. Glycan sequencing faces challenges due to its structural complexity and current detection technology limitations. As a highly sensitive sensor, nanopores can directly convert nucleic acid sequence information into electrical signals, spearheading the revolution of third-generation nucleic acid sequencing technologies. However, their potential for deciphering complex glycans remains untapped. Initial attempts demonstrated the significant sensitivity of nanopores in glycan sensing, which provided the theoretical basis and insights for the realization of nanopore-based glycan sequencing. Here, we present three potential technical routes to employ nanopore technology in glycan sequencing for the first time. The three novel technical routes include: strand sequencing, capturing glycan chains as they translocate through nanopores; sequential hydrolysis sequencing, capturing released monosaccharides one by one; splicing sequencing, mapping signals from hydrolyzed glycan fragments to an oligosaccharide database/library. Designing suitable nanopores, enzymes, and motors, and extracting characteristic signals pose major challenges, potentially aided by artificial intelligence. It would be highly desirable to design an all-in-one high-throughput glycan sequencer instrument by integrating a sample processing unit, nanopore array, and signal acquisition system into a microfluidic device. The nanopore sequencer invention calls for intensive multidisciplinary cooperation including electrochemistry, glycochemistry, engineering, materials, enzymology, etc. Advancing glycan sequencing will promote the development of basic research and facilitate the discovery of glycan-based drugs and disease markers, fostering progress in glycoscience and even life sciences.

Structural identification and anti-neuroinflammatory effects of a pectin-arabinoglucuronogalactan complex, AOPB-1-1, isolated from Asparagus officinalis

Asparagus officinalis L. is a horticultural crop that contains a variety of bioactive compounds with anti-inflammatory effects. Aqueous extracts of A. officinalis can noticeably improve the learning and memory function of model mice. Herein, a pectin-arabinoglucuronogalactan complex (AOPB-1-1) with a relative molecular weight of 90.8 kDa was isolated from A. officinalis. The repeating structural unit of AOPB-1-1 was identified through monosaccharide composition, methylation analysis, uronic acid reduction, partial acid hydrolysis, and nuclear magnetic resonance spectroscopy. AOPB-1-1 contains the rhamnogalacturonan-I (RG-I) domain of pectin polysaccharides (PPs) and arabinoglucuronogalactan (AGG) regions. The backbone of the AGG region is composed of →3,6)-β-D-Galp-(1→ and →4)-β-D-Glcp-(1→ residues substituted at the 4-position to the →4)-α-D-GalAp-(1→ residues of the RG-I main chain. The anti-neuroinflammatory activity of AOPB-1-1 suggests that it can significantly reduce the content of inflammatory cytokines, including nitric oxide (NO), tumor necrosis factor-α (TNF-α), and interleukin-6 (IL-6) and inhibit the expression of inflammatory genes including cyclooxygenase-2 (COX2), nitric oxide synthase (iNOS), TNF-α, IL-6, and interleukin-1β (IL-1β) in LPS-stimulated BV2 cells. Furthermore, its inhibitory effects on TNF-α and IL-6 levels were even better than those of minocycline. The significant anti-neuroinflammatory activity of AOPB-1-1 suggests its applicability as a therapeutic option for the treatment of Alzheimer's disease.

Structural identification and anti-neuroinflammatory effect of a heteropolysaccharide ATP50-3 from Acorus tatarinowii rhizome

Acorus tatarinowii, a famous traditional Chinese medicine, is used for the clinical treatment of memory impairment and dementia. In this research, AT50, the crude polysaccharide extracted from A. tatarinowii rhizome, significantly improved the memory and learning ability of mice with Alzheimer's disease (AD) and exerted excellent anti-neuroinflammatory effects. More importantly, AT50 returned the levels of NO, TNF-α, IL-1β, PGE-2, and IL-6 in AD mouse brains to normal levels. To identify the active ingredients in AT50, a heteropolysaccharide ATP50-3 was obtained from AT50. Structural analysis indicated ATP50-3 consisted of α-L-Araf-(1→, →2)-α-L-Araf-(1→, →3)-α-L-Araf-(1→, →5)-α-L-Araf-(1→, α-D-Xylp-(1→, →3,4)-β-D-Xylp-(1→, →3)-α-D-Galp-(1→, →3,6)-α-D-Galp-(1→, →6)-4-OAc-α-D-Galp-(1→, →3,4,6)-α-D-Galp-(1→, →4)-α-D-Glcp-(1→, →2,3,6)-β-D-Glcp-(1→, →4,6)-α-D-Manp-(1→, →3,4)-α-L-Rhap-(1→, →4)-α-D-GalpA-(1→, and →4)-α-D-GlcpA-(1 → residues and terminated with Xyl and Ara. Additionally, ATP50-3 significantly inhibited the release of proinflammatory factors in lipopolysaccharide-stimulated BV2 cells. ATP50-3 may be an active constituent of AT50, responsible for its anti-neuroinflammatory effects, with great potential to treat AD.

Deciphering the Chemical Language of the Immunomodulatory Properties of Veillonella parvula Lipopolysaccharide

Veillonella parvula, prototypical member of the oral and gut microbiota, is at times commensal yet also potentially pathogenic. The definition of the molecular basis tailoring this contrasting behavior is key for broadening our understanding of the microbiota-driven pathogenic and/or tolerogenic mechanisms that take place within our body. In this study, we focused on the chemistry of the main constituent of the outer membrane of V. parvula, the lipopolysaccharide (LPS). LPS molecules indeed elicit pro-inflammatory and immunomodulatory responses depending on their chemical structures. Herein we report the structural elucidation of the LPS from two strains of V. parvula and show important and unprecedented differences in both the lipid and carbohydrate moieties, including the identification of a novel galactofuranose and mannitol-containing O-antigen repeating unit for one of the two strains. Furthermore, by harnessing computational studies, in vitro human cell models, as well as lectin binding solid-phase assays, we discovered that the two chemically diverse LPS immunologically behave differently and have attempted to identify the molecular determinant(s) governing this phenomenon. Whereas pro-inflammatory potential has been evidenced for the lipid A moiety, by contrast a plausible "immune modulating" action has been proposed for the peculiar O-antigen portion.

Identification of a capsular polysaccharide from Enterococcus faecium U0317 using a targeted approach to discover immunogenic carbohydrates for vaccine development

Enterococcus faecium, a gram-positive opportunistic pathogen, has become a major concern for nosocomial infections due to its resistance to several antibiotics, including vancomycin. Finding novel alternatives for treatment prevention, such as vaccines, is therefore crucial. In this study, we used various techniques to discover a novel capsular polysaccharide. Firstly, we identified an encapsulated E. faecium strain by evaluating the opsonophagocytic activity of fifteen strains with antibodies targeting the well-known lipoteichoic acid antigen. This activity was attributed to an unknown polysaccharide. We then prepared a crude cell wall glycopolymer and fractionated it, guided by immunodot-blot analysis. The most immunoreactive fractions were used for opsonophagocytic inhibition assays. The fraction containing the inhibitory polysaccharide underwent structural characterization using NMR and chemical analyses. The elucidated structure presents a branched repeating unit, with the linear part being: →)-β-d-Gal-(1 → 4)-β-d-Glc-(1 → 4)-β-d-Gal-(1 → 4)-β-d-GlcNAc-(1→, further decorated with a terminal α-d-Glc and a d-phosphoglycerol moiety, attached to O-2 and O-3 of the 4-linked Gal unit, respectively. This polysaccharide was conjugated to BSA and the synthetic glycoprotein used to immunize mice. The resulting sera exhibited good opsonic activity, suggesting its potential as a vaccine antigen. In conclusion, our effector-function-based approach successfully identified an immunogenic capsular polysaccharide with promising applications in immunotherapy.

Functional redundancy revealed by the deletion of the mimivirus GMC-oxidoreductase genes

The mimivirus 1.2 Mb genome was shown to be organized into a nucleocapsid-like genomic fiber encased in the nucleoid compartment inside the icosahedral capsid. The genomic fiber protein shell is composed of a mixture of two GMC-oxidoreductase paralogs, one of them being the main component of the glycosylated layer of fibrils at the surface of the virion. In this study, we determined the effect of the deletion of each of the corresponding genes on the genomic fiber and the layer of surface fibrils. First, we deleted the GMC-oxidoreductase, the most abundant in the genomic fiber, and determined its structure and composition in the mutant. As expected, it was composed of the second GMC-oxidoreductase and contained 5- and 6-start helices similar to the wild-type fiber. This result led us to propose a model explaining their coexistence. Then we deleted the GMC-oxidoreductase, the most abundant in the layer of fibrils, to analyze its protein composition in the mutant. Second, we showed that the fitness of single mutants and the double mutant were not decreased compared with the wild-type viruses under laboratory conditions. Third, we determined that deleting the GMC-oxidoreductase genes did not impact the glycosylation or the glycan composition of the layer of surface fibrils, despite modifying their protein composition. Because the glycosylation machinery and glycan composition of members of different clades are different, we expanded the analysis of the protein composition of the layer of fibrils to members of the B and C clades and showed that it was different among the three clades and even among isolates within the same clade. Taken together, the results obtained on two distinct central processes (genome packaging and virion coating) illustrate an unexpected functional redundancy in members of the family Mimiviridae, suggesting this may be the major evolutionary force behind their giant genomes.

Structural and in vivo-in vitro myocardial injury protection features of two novel polysaccharides from Allium macrostemon Bunge and Allium chinense G. Don

This study aimed to investigate the structural characteristics, in vivo antiatherosclerosis activity, and in vitro myocardial injury protection effects of polysaccharides from Allium macrostemon Bunge and Allium chinense G. Don. Thus, crude polysaccharides of Allium macrostemon Bunge and Allium chinense G. Don significantly reduced serum lipid levels, improved cardiac myocyte morphology and arrangement, and relieved the development of myocardial fibrosis. Meanwhile, the lesion areas of the aorta and aortic valve had evident visual improvements. Furthermore, two main novel purified polysaccharides, namely, AMB-1 and ACGD-1, were isolated and characterized from crude Allium macrostemon Bunge and Allium chinense G. Don fractions, respectively. The purified polysaccharides mainly consisted of fructose and glucose and had molecular weights of 25.22 and 19.53 kDa, respectively. In addition, Fourier transform infrared spectroscopy, methylation, and nuclear magnetic resonance data revealed the primary structures of the AMB1 (or ACGD1) backbone with branched side chains. Scanning electron microscope analysis showed that the purified polysaccharides were both piled together in a lamellar or clastic form with a smooth surface along with linear or irregular bulges. Moreover, the purified polysaccharides both showed nontoxicity on H9c2 cells and effectively dropped hypoxia/reoxygenation-induced apoptosis by the BCL-2/BAX pathway. Overall, the characterization of the structural properties and in vivo and in vitro myocardial injury protection effects of Allium macrostemon Bunge and Allium chinense G. Don polysaccharides enriched our understanding of their nutritional and medicinal values. To the best of our knowledge, this is the first study on the structural characteristics and bioactivities of Allium chinense G. Don polysaccharides.

Characterisation of a capsular polysaccharide from Moraxella nonliquefaciens CCUG 348T

Moraxella nonliquefaciens is a commensal of the human upper respiratory tract (URT) but on rare occasions is recovered in cases of ocular, septic and pulmonary infections. Hence there is interest in the pathogenic determinants of M. nonliquefaciens, of which outer membrane (OM) structures such as fimbriae and two capsular polysaccharide (CPS) structures, →3)-β-D-GalpNAc-(1→5)-β-Kdop-(2→ and →8)-α-NeuAc-(2→, have been reported in the literature. To further characterise its surface virulence factors, we isolated a novel CPS from M. nonliquefaciens type strain CCUG 348T. This structure was elucidated using NMR data obtained from CPS samples that were subjected to various degrees of mild acid hydrolysis. Together with GLC-MS data, the structure was resolved as a linear polymer composed of two GalfNAc residues consecutively added to Kdo, →3)-β-D-GalfNAc-(1→3)-α-D-GalfNAc-(1→5)-α-(8-OAc)Kdop-(2→. Supporting evidence for this material being CPS was drawn from the proposed CPS biosynthetic locus which encoded a potential GalfNAc transferase, a UDP-GalpNAc mutase for UDP-GalfNAc production and a putative CPS polymerase with predicted GalfNAc and Kdo transferase domains. This study describes a unique CPS composition reported in Moraxella spp. and offers genetic insights into the synthesis and expression of GalfNAc residues, which are rare in bacterial OM glycans.

Nuclear magnetic resonance-based structural elucidation of novel marine glycans and derived oligosaccharides

Marine glycans of defined structures are unique representatives among all kinds of structurally complex glycans endowed with important biological actions. Besides their unique biological properties, these marine sugars also enable advanced structure-activity relationship (SAR) studies given their distinct and defined structures. However, the natural high molecular weights (MWs) of these marine polysaccharides, sometimes even bigger than 100 kDa, pose a problem in many biophysical and analytical studies. Hence, the preparation of low MW oligosaccharides becomes a strategy to overcome the problem. Regardless of the polymeric or oligomeric lengths of these molecules, structural elucidation is mandatory for SAR studies. For this, nuclear magnetic resonance (NMR) spectroscopy plays a pivotal role. Here, we revisit the NMR-based structural elucidation of a series of marine sulfated poly/oligosaccharides discovered in our laboratory within the last 2 years. This set of structures includes the α-glucan extracted from the bivalve Marcia hiantina; the two sulfated galactans extracted from the red alga Botryocladia occidentalis; the fucosylated chondroitin sulfate isolated from the sea cucumber Pentacta pygmaea; the oligosaccharides produced from the fucosylated chondroitin sulfates from this sea cucumber species and from another species, Holothuria floridana; and the sulfated fucan from this later species. Specific 1H and 13C chemical shifts, generated by various 1D and 2D homonuclear and heteronuclear NMR spectra, are exploited as the primary source of information in the structural elucidation of these marine glycans.

MA'AT Analysis: Unbiased Multi-State Conformational Modeling of Exocyclic Hydroxymethyl Group Conformation in Methyl Aldohexopyranosides

MA'AT analysis (J. Chem. Inf. Model. 2022, 62, 3135-3141) has been applied to model exocyclic hydroxymethyl group conformation in methyl β-D-glucopyranoside (βGlcOMe), methyl β-D-galactopyranoside (βGalOMe), and methyl β-D-mannopyranoside (βManOMe) in an unbiased manner. Using up to eight NMR J-couplings sensitive to rotation about the C5-C6 bond (torsion angle ω), two-state models of ω were obtained that are qualitatively consistent with the relative populations of the gg, gt, and tg rotamers reported previously. MA'AT analysis gave consistent unbiased gt ⇌ tg models of ω in βGalOMe, with gt more populated than tg and mean values of ω for each population similar to those obtained from aqueous 1-μs MD simulation. Using different combinations of J-couplings had little effect on the βGalOMe model in terms of the mean values of ω and circular standard deviations (CSDs). In contrast, MA'AT analysis of ω in βGlcOMe and βManOMe produced more than one two-state model independent of the ensemble of J-values used in the analyses. These models were characterized by gg ⇌ gt conformer exchange as expected, but the mean values of ω in both conformers varied significantly in the different fits, especially for the gg rotamer. Constrained (biased) MA'AT analyses in which only staggered geometries about ω were allowed gave RMSDs slightly larger than those obtained from the unbiased fits, precluding an assignment of an unbiased model. It is unclear why MA'AT analysis gives consistent and predictable unbiased models of ω in βGalOMe but not in βGlcOMe and βManOMe. One possibility is that the distribution of ω in one or both of the gg and gt conformers in the latter does not conform to a von Mises function (i.e., is not Gaussian-like), but rather to a broad and/or flat distribution that cannot be fit by the current version of MA'AT. Nevertheless, the results of this study provide new evidence of the ability of MA'AT analysis to treat multi-state conformational exchange using only experimental NMR data, extending recent MA'AT applications to furanosyl ring pseudorotation (Biochemistry 2022, 61, 239-251).

Multi-step semi-synthesis, structural characterization and growth factor interaction study of regiochemically sulfated diabolican polysaccharides

Diabolican is an exopolysaccharide (EPS) produced by Vibrio diabolicus HE800, a mesophilic bacterium firstly isolated from a deep-sea hydrothermal field. Its glycosaminoglycan (GAG)-like structure, consisting of a tetrasaccharide repeating unit composed of two aminosugars (N-acetyl-glucosamine and N-acetyl-galactosamine) and two glucuronic acid units, suggested to subject it to regioselective sulfation processes, in order to obtain some sulfated derivatives potentially acting as GAG mimics. To this aim, a multi-step semi-synthetic approach, relying upon tailored sequence of regioselective protection, sulfation and deprotection steps, was employed in this work. The chemical structure of the obtained sulfated diabolican derivatives was characterized by a multi-technique analytic approach, in order to define both degree of sulfation (DS) and sulfation pattern within the polysaccharide repeating unit, above all. Finally, binding affinity for some growth factors relevant for biomedical applications was measured for both starting diabolican and sulfated derivatives thereof. Collected data suggested that sulfation pattern could be a key structural element for the selective interaction with signaling proteins not only in the case of native GAGs, as already known, but also for GAG-like structures obtained by regioselective sulfation of naturally unsulfated polysaccharides.

Machine learning-based correction for spin-orbit coupling effects in NMR chemical shift calculations

As one of the most powerful analytical methods for molecular and solid-state structure elucidation, NMR spectroscopy is an integral part of chemical laboratories associated with a great research interest in its computational simulation. Particularly when heavy atoms are present, a relativistic treatment is essential in the calculations as these influence also the nearby light atoms. In this work, we present a Δ-machine learning method that approximates the contribution to 13C and 1H NMR chemical shifts that stems from spin-orbit (SO) coupling effects. It is built on computed reference data at the spin-orbit zeroth-order regular approximation (ZORA) DFT level for a set of 6388 structures with 38 740 13C and 64 436 1H NMR chemical shifts. The scope of the methods covers the 17 most important heavy p-block elements that exhibit heavy atom on the light atom (HALA) effects to covalently bound carbon or hydrogen atoms. Evaluated on the test data set, the approach is able to recover roughly 85% of the SO contribution for 13C and 70% for 1H from a scalar-relativistic PBE0/ZORA-def2-TZVP calculation at virtually no extra computational costs. Moreover, the method is transferable to other baseline DFT methods even without retraining the model and performs well for realistic organotin and -lead compounds. Finally, we show that using a combination of the new approach with our previous Δ-ML method for correlation contributions to NMR chemical shifts, the mean absolute NMR shift deviations from non-relativistic DFT calculations to experimental values can be halved.

Structural elucidation of novel pro-inflammatory polysaccharides from Daphne mezereum L

Daphne mezereum L., an important medicinal plant in Scandinavian folk medicine, was used to treat ailments such as diarrhea, swelling and stomach pain. A range of natural compounds have been isolated, but little attention has been given to the polysaccharides in this plant. Previous work in our group have shown that a polysaccharide enriched fraction from the bark of D. mezereum exhibited pro-inflammatory effects. To pursue this further, the aim of the present work was to isolate and characterize these polysaccharides. From the ethanol-precipitate of a water extract, one neutral (DMP-NF) and one acidic (DMP-AF) fraction was isolated by anion-exchange chromatography. GC, GC-MS and 1D- and 2D-NMR were used to characterize the polysaccharide structures. DMP-NF appeared to be a mixture of arabinan, arabinogalactan and hemicelluloses such as xyloglucan, mannan and xylan. DMP-AF contained a pectic polysaccharide mainly consisting of an unusually long homogalacturonan backbone. Enzymatic treatment by pectinase of DMP-AF yielded DMP-ED, which contained a rhamnogalacturonan-I backbone with arabinan, galactan and arabinogalactan side chains. Both DMP-NF and DMP-ED induced IFN-γ and TNF-α secretion in peripheral blood mononuclear cells (PBMCs), DMP-ED being the most potent fraction. DMP-AF was less active, which might be due to a less sterically available rhamnogalacturonan-I domain.

Covalent connectivity of glycogen in brewer's spent yeast cell walls revealed by enzymatic approaches and dynamic nuclear polarization NMR

Yeast cell walls undergo modifications during the brewing process, leading to a remodelling of their architecture. One significant change is the increased insolubility of the cell wall glycogen pool, likely due to the formation of covalent bonds between glycogen and cell wall polysaccharides. To verify this hypothesis, we extracted the brewer's spent yeast with 4 M KOH, obtaining an insoluble glucan fraction (AE.4 M) primarily composed of (α1 → 4)- and (1 → 3)-linked Glc residues. Dynamic nuclear polarization solid-state NMR of AE.4 M revealed distinct glucan resonances that helped to differentiate between α- and β glucosyl (1 → 4)-linked residues, and confirm covalent linkages between (β1 → 3)-glucans and glycogen through a (β1 → 4)-linkage. The hydrolysis with different endo-glucanases (zymolyase, cellulase, and lichenase) was used to obtain solubilized high molecular weight glycogen fractions. NMR analysis showed that covalent links between glycogen and (β1 → 6)-glucans through (α1 → 6) glycosidic linkage, with branching at the C6 position involving (β1 → 3), and (β1 → 6)-glucans. HPAEC-PAD analysis of the enzymatically released oligosaccharides confirmed covalent linkages of (β1 → 3), (β1 → 6)-, and (β1 → 4)-glucan motifs with (α1 → 4)-glucans. This combination of multiple enzymatic approaches and NMR methods shed light into the role of yeast cell wall glycogen as a structural core covalently linked to other cell wall components during the brewing process.

The Relationship between Preparation and Biological Activities of Animal-Derived Polysaccharides: A Comprehensive Review

Polysaccharides are biomolecules found in microorganisms, plants, and animals that constitute living organisms. Glycosaminoglycans, unique acidic polysaccharides in animal connective tissue, are often combined with proteins in the form of covalent bonds due to their potent biological activity, low toxicity, and minimal side effects, which have the potential to be utilized as nutrition healthcare and dietary supplements. Existing studies have demonstrated that the bioactivity of polysaccharides is closely dependent on their structure and chain conformation. The characteristic functional groups and primary structure directly determine the strength of activity. However, the relationship between structure and function is still unclear, and the target and mechanism of action are not fully understood, resulting in limited clinical applications. As a result, the clinical applications of these polysaccharides are currently limited. This review provides a comprehensive summary of the extraction methods, structures, and biological activities of animal-derived polysaccharides that have been discovered so far. The aim is to promote developments in animal active polysaccharide science and provide theoretical support for exploring other unknown natural products.

Production and characterization of starch-lignin based materials: A review

In their pristine state, starch and lignin are abundant and inexpensive natural polymers frequently considered green alternatives to oil-based and synthetic polymers. Despite their availability and owing to their physicochemical properties; starch and lignin are not often utilized in their pristine forms for high-performance applications. Generally, chemical and physical modifications transform them into starch- and lignin-based materials with broadened properties and functionality. In the last decade, the combination of starch and lignin for producing reinforced materials has gained significant attention. The reinforcing of starch matrices with lignin has received primary focus because of the enhanced water sensitivity, UV protection, and mechanical and thermal resistance that lignin introduces to starch-based materials. This review paper aims to assess starch-lignin materials' production and characterization technologies, highlighting their physicochemical properties, outcomes, challenges, and opportunities. First, this paper describes the current status, sources, and chemical modifications of lignin and starch. Next, the discussion is oriented toward starch-lignin materials and their production approaches, such as blends, composites, plasticized/crosslinked films, and coupled polymers. Special attention is given to the characterization methods of starch-lignin materials, focusing on their advantages, disadvantages, and expected outcomes. Finally, the challenges, opportunities, and future perspectives in developing starch-lignin materials, such as adhesives, coatings, films, and controlled delivery systems, are discussed.

N-glycosylation in Archaea: Unusual sugars and unique modifications

Archaea are microorganisms that comprise a distinct branch of the universal tree of life and which are best known as extremophiles, residing in a variety of environments characterized by harsh physical conditions. One seemingly universal trait of Archaea is the ability to perform N-glycosylation. At the same time, archaeal N-linked glycans present variety in terms of both composition and architecture not seen in the parallel eukaryal or bacterial processes. In this mini-review, many of the unique and unusual sugars found in archaeal N-linked glycans as identified by nuclear magnetic resonance spectroscopy are described.

Preparation, structures, and biological functions of rhamnan sulfate from green seaweed of the genus Monostroma: A review

Rhamnan sulfate, a rhamnose-rich sulfated polysaccharide, is present in the cell walls of green seaweed belonging to the genus Monostroma. This macromolecule demonstrates promising therapeutic properties, including anti-coagulant, thrombolytic, anti-viral, anti-obesity, and anti-inflammatory activities, which hold potential applications in food and medical industries. However, rhamnan sulfate has not garnered as much attention from researchers as other seaweed polysaccharides, including alginate, carrageenan, and fucoidan. This review discusses the extraction and purification techniques of rhamnan sulfate, delves into its chemical structures and related elucidation approaches, and provides an overview of its biological functions. Future research should focus on the structure-activity relationship of rhamnan sulfate and the industrial preparation of rhamnan sulfate with a specific homogeneous structure to facilitate its practical applications.

Lipopolysaccharides from Ralstonia solanacearum induce a broad metabolomic response in Solanum lycopersicum

Ralstonia solanacearum, one of the most destructive crop pathogens worldwide, causes bacterial wilt disease in a wide range of host plants. The major component of the outer membrane of Gram-negative bacteria, lipopolysaccharides (LPS), has been shown to function as elicitors of plant defense leading to the activation of signaling and defense pathways in several plant species. LPS from a R. solanacearum strain virulent on tomato (LPSR. sol.), were purified, chemically characterized, and structurally elucidated. The lipid A moiety consisted of tetra- to hexa-acylated bis-phosphorylated disaccharide backbone, also decorated by aminoarabinose residues in minor species, while the O-polysaccharide chain consisted of either linear tetrasaccharide or branched pentasaccharide repeating units containing α-L-rhamnose, N-acetyl-β-D-glucosamine, and β-L-xylose. These properties might be associated with the evasion of host surveillance, aiding the establishment of the infection. Using untargeted metabolomics, the effect of LPSR. sol. elicitation on the metabolome of Solanum lycopersicum leaves was investigated across three incubation time intervals with the application of UHPLC-MS for metabolic profiling. The results revealed the production of oxylipins, e.g., trihydroxy octadecenoic acid and trihydroxy octadecadienoic acid, as well as several hydroxycinnamic acid amide derivatives, e.g., coumaroyl tyramine and feruloyl tyramine, as phytochemicals that exhibit a positive correlation to LPSR. sol. treatment. Although the chemical properties of these metabolite classes have been studied, the functional roles of these compounds have not been fully elucidated. Overall, the results suggest that the features of the LPSR. sol. chemotype aid in limiting or attenuating the full deployment of small molecular host defenses and contribute to the understanding of the perturbation and reprogramming of host metabolism during biotic immune responses.

Development of Conjugated Kefiran-Chondroitin Sulphate Cryogels with Enhanced Properties for Biomedical Applications

Hydrogels based on natural polysaccharides can have unique properties and be tailored for several applications, which may be mainly limited by the fragile structure and weak mechanical properties of this type of system. We successfully prepared cryogels made of newly synthesized kefiran exopolysaccharide-chondroitin sulfate (CS) conjugate via carbodiimide-mediated coupling to overcome these drawbacks. The freeze-thawing procedure of cryogel preparation followed by lyophilization is a promising route to fabricate polymer-based scaffolds with countless and valuable biomedical applications. The novel graft macromolecular compound (kefiran-CS conjugate) was characterized through ¹H-NMR and FTIR spectroscopy-which confirmed the structure of the conjugate, differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA)-which mirrored good thermal stability (degradation temperature of about 215 °C) and, finally, gel permeation chromatography-size exclusion chromatography (GPC-SEC)-which proved an increased molecular weight due to chemical coupling of kefiran with CS. At the same time, the corresponding cryogels physically crosslinked after the freeze-thawing procedure were investigated by scanning electron microscopy (SEM), Micro-CT, and dynamic rheology. The results revealed a prevalent contribution of elastic/storage component to the viscoelastic behavior of cryogels in swollen state, a micromorphology with micrometer-sized open pores fully interconnected, and high porosity (ca. 90%) observed for freeze-dried cryogels. Furthermore, the metabolic activity and proliferation of human adipose stem cells (hASCs), when cultured onto the developed kefiran-CS cryogel, was maintained at a satisfactory level over 72 h. Based on the results obtained, it can be inferred that the newly freeze-dried kefiran-CS cryogels possess a host of unique properties that render them highly suitable for use in tissue engineering, regenerative medicine, drug delivery, and other biomedical applications where robust mechanical properties and biocompatibility are crucial.

Ensemble determination by NMR data deconvolution

Nuclear magnetic resonance (NMR) is the spectroscopic technique of choice for determining molecular conformations in solution at atomic resolution. As solution NMR spectra are rich in structural and dynamic information, the way in which the data should be acquired and handled to deliver accurate ensembles is not trivial. This Review provides a guide to the NMR experiment selection and parametrization process, the generation of viable theoretical conformer pools and the deconvolution of time-averaged NMR data into a conformer ensemble that accurately represents a flexible molecule in solution. In addition to reviewing the key elements of solution ensemble determination of flexible mid-sized molecules, the feasibility and pitfalls of data deconvolution are discussed with a comparison of the performance of representative algorithms.

Structural Determination and Chemical Synthesis of the N-Glycan from the Hyperthermophilic Archaeon Thermococcus kodakarensis

Asparagine-linked protein glycosylations (N-glycosylations) are one of the most abundant post-translational modifications and are essential for various biological phenomena. Herein, we describe the isolation, structural determination, and chemical synthesis of the N-glycan from the hyperthermophilic archaeon Thermococcus kodakarensis. The N-glycan from the organism possesses a unique structure including myo-inositol, which has not been found in previously characterized N-glycans. In this structure, myo-inositol is highly glycosylated and linked with a disaccharide unit through a phosphodiester. The straightforward synthesis of this glycan was accomplished through diastereoselective phosphorylation and phosphodiester construction by S_N 2 coupling. Considering the early divergence of hyperthermophilic organisms in evolution, this study can be expected to open the door to approaching the primitive function of glycan modification at the molecular level.

Structure characterization of pectin from the pollen of Typha angustifolia L. and the inhibition activity of lipid accumulation in oleic acid induced L02 cells

The pollen of Typha angustifolia L. decoction was clinically used to treat hyperlipidemia in China. A pectin polysaccharide (PTPS-2-2) was obtained from T. angustifolia pollen through water extraction, ion-exchange chromatography, and gel chromatography. Structural characterization showed that PTPS-2-2 had a molecular weight of 54 kDa and was composed of rhamnose, arabinose, xylose, galactose, and galacturonic acid with a molar ratio of 11.5: 36.5: 4.1: 36.7: 11.2. PTPS-2-2 consisted of rhamnogalacturonan I (RG-I) and arabinogalactan II (AG-II) domains. Its backbone was predominantly composed of →4-α-D-GalpA-(1 → 2)-α-L-Rhap-(1→, with branches of 1,3-Galp, 1,6-Galp, 1,3,6-Galp, T-Araf, 1.5-Araf and T-Xylp, connected to the 4-position of 1,2-Rhap and the 3-position of 1,4-GalpA. The inhibitory effect of PTPS-2-2 on lipid accumulation was studied in vitro, using L02 cells induced by oleic acid. This experiment shows that PTPS-2-2 treatment at 100-400 μg/mL dose-dependently reduce cellular triglycerides (TG), cholesterol (TC), aspartate aminotransferase (AST), alanine aminotransferase (ALT) and malondialdehyde (MDA) levels, while elevated superoxide dismutase (SOD) levels. This indicated that PTPS-2-2 potentially ameliorated oleic acid-induced hepatic steatosis by inhibiting lipid accumulation and oxidative stress.

Recent advances in microfluidics-based bioNMR analysis

Nuclear magnetic resonance (NMR) has been used in a variety of fields due to its powerful analytical capability. To facilitate biochemical NMR (bioNMR) analysis for samples with a limited mass, a number of integrated systems have been developed by coupling microfluidics and NMR. However, there are few review papers that summarize the recent advances in the development of microfluidics-based NMR (μNMR) systems. Herein, we review the advancements in μNMR systems built on high-field commercial instruments and low-field compact platforms. Specifically, μNMR platforms with three types of typical microcoils settled in the high-field NMR instruments will be discussed, followed by summarizing compact NMR systems and their applications in biomedical point-of-care testing. Finally, a conclusion and future prospects in the field of μNMR were given.

Structural characterization and immunomodulatory activity of an exopolysaccharide from marine-derived Aspergillus versicolor SCAU141

Until now, relatively little is known about marine-derived fungal polysaccharides and their activities. Exopolysaccharide AVP141-A was isolated from the broth of marine-derived fungus Aspergillus versicolor SCAU141 and purified by Diethylaminoethyl-Sepharose Fast Flow and Sephadex G-100. The structural characteristics of AVP141-A was studied by chemical analysis together with high-performance gel permeation chromatography, ion chromatography, Fourier-transform infrared spectroscopy, gas chromatography-mass spectrometry and nuclear magnetic resonance spectroscopy. The results showed that AVP141-A with the molecular weight of 5.10 kDa was mainly composed of →4)-α-D-Glcp-(1→, branched by α-D-Glcp-(1→ and →6)-α-D-Glcp-(1→ at C-6 positions of the glucan backbone. In particular, sulfate ester (approximately 3.62 %) was found in AVP141-A, which was frequently considered to occur in marine-derived microbial polysaccharides rather than other microbial polysaccharides. Furthermore, AVP141-A significantly enhanced the activity of the inflammatory factors NO, COX-2 and TNF-α in RAW264.7 macrophages by activating the MAPK/p38 and NF-κB/p65 pathways. In addition, metabolomic analysis revealed that most of the pathways with significant changes in RAW264.7 macrophages treated with AVP141-A were amino acid-related pathways, and arginine was the characteristic metabolite. In conclusion, this study identified AVP141-A as a marine fungus-derived sulfated exopolysaccharide with potential for development as an immune activator.

Characterization of Burkholderia pseudomallei O antigens in different clinical strains

O antigen is the major component of lipopolysaccharide LPS. The chemical structure of the O antigen determines the LPS serospecificity of the bacteria, and the diversity of O antigen is the basis for serotyping Burkholderia pseudomallei. In this study, structural elucidation of type B O antigen obtained from a clinical B. pseudomallei strain was conducted, and the effects of different types of LPS on macrophage differentiation were investigated. The O antigen was found to be composed of repeating units of [→4)-α-L-Rhap(1 → 4)-α-L-Rhap(1→2)-α-L-Rhap(1 → 2)-α-L-Rhap(1 → 3)-α-L-Rhap(1 → 3)-α-L-Rhap(1 → 4)-α-L-Rhap(1 → 6)-α-D-Galp(1→]_n, where some of the →4)-α-L-Rhap(1 → units were substituted at O-3 by β-D-Xylp(1 → residues, and minor →3)-α-L-Rhap(1 → units were substituted at O-2 by β-D-Xylp(1 → residues. Meahwhile, the →6)-α-D-Galp(1 → units were substituted at O-3 by α-D-Galp(1 → residues. Furthermore, both type A and type B O antigens of B. pseudomallei could polarize macrophages toward the M1 phenotype, but the core oligosaccharides had no such activity. Therefore, we deduced that this polarization relies on the O antigen of LPS and might be related to the ability of B. pseudomallei to survive and replicate within macrophages. Thus, the characterization of different types of O antigen structural motifs is essential for further clarifying the persistence/survival mechanisms and inflammatory potential of B. pseudomallei.

Primary Structure of Glycans by NMR Spectroscopy

Glycans, carbohydrate molecules in the realm of biology, are present as biomedically important glycoconjugates and a characteristic aspect is that their structures in many instances are branched. In determining the primary structure of a glycan, the sugar components including the absolute configuration and ring form, anomeric configuration, linkage(s), sequence, and substituents should be elucidated. Solution state NMR spectroscopy offers a unique opportunity to resolve all these aspects at atomic resolution. During the last two decades, advancement of both NMR experiments and spectrometer hardware have made it possible to unravel carbohydrate structure more efficiently. These developments applicable to glycans include, inter alia, NMR experiments that reduce spectral overlap, use selective excitations, record tilted projections of multidimensional spectra, acquire spectra by multiple receivers, utilize polarization by fast-pulsing techniques, concatenate pulse-sequence modules to acquire several spectra in a single measurement, acquire pure shift correlated spectra devoid of scalar couplings, employ stable isotope labeling to efficiently obtain homo- and/or heteronuclear correlations, as well as those that rely on dipolar cross-correlated interactions for sequential information. Refined computer programs for NMR spin simulation and chemical shift prediction aid the structural elucidation of glycans, which are notorious for their limited spectral dispersion. Hardware developments include cryogenically cold probes and dynamic nuclear polarization techniques, both resulting in enhanced sensitivity as well as ultrahigh field NMR spectrometers with a ¹H NMR resonance frequency higher than 1 GHz, thus improving resolution of resonances. Taken together, the developments have made and will in the future make it possible to elucidate carbohydrate structure in great detail, thereby forming the basis for understanding of how glycans interact with other molecules.

Extraction, Purification, and Chemical Degradation of LPS from Gut Microbiota Strains

It is estimated that more than 500 different bacterial species colonize the human gut, and they are collectively known as the gut microbiota. Such a massive bacterial presence is now considered an additional organ of the human body, thus becoming the object of an intense and daily growing research activity. Gram-negative bacteria represent a large percentage of the gut microbiota strains. The main constituent of the outer membrane of Gram-negatives is the lipopolysaccharide (LPS). Since its first discovery, LPS has been extensively studied for its structure-dependent capability to elicit a potent immune inflammatory reaction when perceived by specific immune receptors present in our body. Therefore, traditionally, LPS, due to its peculiar chemistry, has been associated with pathogenic bacteria, and it has been extensively studied for its dangerous effects on human health. However, LPS is also expressed on the cell surface of harmless and beneficial bacteria that colonize our intestines. This necessarily implies that the LPS from harmless gut microbes is "chemically different" from that owned by pathogenic ones, hence enabling successful colonization of the intestinal tract without creating a threat to the host immune system. Deciphering the structural features of LPS from these gut bacteria is essential to improve our still scarce knowledge of how the human host lives in a harmonious relationship with its own microbiota. To this end, LPS extraction and purification are essential steps in this field of research. Yet working with gut bacteria is extremely complex for a number of reasons, one being related to the fact that they produce an array of other glycans and glycoconjugates, such as capsular polysaccharides and/or exopolysaccharides, which render the isolation and characterization of the sole LPS not at all trivial. Here, we provide a protocol that might help when dealing with LPS from gut microbial species. We describe the preliminary manipulations and checks, extraction, and purification approaches, as well as the necessary chemical manipulations that should be performed to enable the characterization of the structure of an LPS by means of techniques like nuclear magnetic resonance spectroscopy and mass spectrometry.

An arabinogalactan isolated from Pollen Typhae induces the apoptosis of RKO cells by promoting macrophage polarization

An arabinogalactan (PTPS-1-2) was isolated and characterized from Pollen Typhae, and its potential antitumor effects on activating macrophages to produce immunomodulatory factors and promoting apoptosis in colorectal cancer cells were investigated. Structural characterization showed that PTPS-1-2 had a molecular weight of 59 kDa and was composed of rhamnose, arabinose, glucuronic acid, galactose, and galacturonic acid with a molar ratio of 7.6: 17.1: 6.5: 61.4: 7.4. Its backbone was predominantly composed of T-β-D-Galp, 1,3-β-D-Galp, 1,6-β-D-Galp, 1,3,6-β-D-Galp, 1,4-α-D-GalpA, 1,2-α-L-Rhap, additionally, branches contained 1,5-α-L-Araf, T-α-L-Araf, T-β-D-4-OMe-GlcpA, T-β-D-GlcpA and T-α-L-Rhap. PTPS-1-2 activated RAW264.7 cell by triggering the NF-kB signaling pathway and M1 macrophage polarization. Furthermore, the conditioned medium (CM) of Mφ pretreated with PTPS-1-2 exerted marked antitumor effects by inhibiting RKO cell proliferation and suppressing cell colony formation. Collectively, our findings suggested that PTPS-1-2 might be a therapeutic option for the prevention and treatment of tumors.

Synthetic Approaches to Break the Chemical Shift Degeneracy of Glycans

NMR spectroscopy is the leading technique for determining glycans' three-dimensional structure and dynamic in solution as well as a fundamental tool to study protein-glycan interactions. To overcome the severe chemical shift degeneracy of these compounds, synthetic probes carrying NMR-active nuclei (e. g., ¹³ C or ¹⁹ F) or lanthanide tags have been proposed. These elegant strategies permitted to simplify the complex NMR analysis of unlabeled analogues, shining light on glycans' conformational aspects and interaction with proteins. Here, we highlight some key achievements in the synthesis of specifically labeled glycan probes and their contribution towards the fundamental understanding of glycans.

An anticomplement homogeneous polysaccharide from Hedyotis diffusa attenuates lipopolysaccharide-induced acute lung injury and inhibits neutrophil extracellular trap formation

BACKGROUND

Owing to the involvement of the overactivated complement system in acute lung injury (ALI) development, anticomplement components may attenuate ALI. Hedyotis diffusa is a traditional Chinese medicine for treating lung heat and its crude polysaccharides (HDP) exhibit significant anticomplement activity in vitro.

PURPOSE

To obtain an anticomplement homogeneous polysaccharide from HDP and verify its therapeutic effect and mechanism on ALI.

METHODS

Diethylaminoethyl-52 (DEAE-52) cellulose and gel permeation columns were used to isolate a homogeneous polysaccharide HD-PS-3, which was then characterized using nuclear magnetic resonance (NMR) and methylation analysis. In vitro, the anticomplement activities of HD-PS-3 through classical and alternative pathways were determined using a hemolytic test. The therapeutic effects of HDP and HD-PS-3 on ALI were evaluated in lipopolysaccharide (LPS) intratracheal instilled mice. Hematoxylin and eosin (H&E) staining, enzyme-linked immunosorbent assay (ELISA), and immunohistochemical staining were used to assess histological changes, measure cytokine levels, and evaluate the degree of complement component 3c (C3c) deposition and neutrophil infiltration, respectively. ELISA, western blotting, and immunofluorescence were used to analyze neutrophil extracellular trap (NET) formation.

RESULTS

From HDP, 1.5 g of the homogeneous polysaccharide HD-PS-3 was obtained. HD-PS-3 was an acidic heteropolysaccharide with an acetyl group, which was composed of →4,6)-α-Glcp-(1→, →3,4)-α-Glcp-(1→, →4)-α-Glcp-(1→, →4,6)-α-Galp-(1→, →5)-α-Araf-(1→, α-Rhap-(1→, α-Araf-(1→, α-GlcpA-(1→, →4)-β-Manp-(1→, β-Manp-(1→ and →3)-β-Manp-(1→. The in vitro results suggest that HD-PS-3 exhibited anticomplement activity with CH₅₀ and AP₅₀ values of 115 ± 12 μg/ml and 307 ± 11 μg/ml, respectively. After confirming the efficacy of HDP (200 mg/kg) in attenuating lung injury, the effect of HD-PS-3 on ALI was also investigated. HD-PS-3 (75 and 150 mg/kg) attenuated LPS-induced ALI as well, evidenced by lung pathology, lung injury scores, protein concentration, leukocyte counts, tumor necrosis factor-α (TNF-α), and interleukin-6 (IL-6) contents in bronchoalveolar lavage fluid (BALF). Mechanistically, HD-PS-3 inhibited complement activation, manifested in reduced pulmonary C3c deposition in lung tissue and complement component 3a (C3a) content in BALF. Neutrophil recruitment was also reduced by HD-PS-3, with significantly reduced pulmonary neutrophil infiltration and lower levels of C-X-C motif chemokine ligand 1 (CXCL1) and myeloperoxidase (MPO) in BALF. In addition, HD-PS-3 reduced the levels of MPO-DNA complex in BALF, decreased citrullinated histone H3 (Cit H3) expression and NET formation (colocalization of MPO, Cit H3, and DNA) in lung tissue.

CONCLUSION

An anticomplement homogeneous polysaccharide HD-PS-3 was isolated from H. diffusa. HD-PS-3 exhibited a therapeutic effect against ALI, and the mechanism might be related to its inhibitory effects on complement activation, neutrophil recruitment, and NET formation.

Structure of the Lipooligosaccharide from the Deep-Sea Marine Bacterium Idiomarina zobellii KMM 231T, Isolated at a Depth of 4000 Meters

The structural characterization of lipopolysaccharides has critical implications for some biomedical applications, and marine bacteria are an inimitable source of new glyco-structures potentially usable in medicinal chemistry. On the other hand, lipopolysaccharides of marine Gram-negative bacteria present certain structural features that can help the understanding of the adaptation processes. The deep-sea marine Gram-negative bacterium Idiomarina zobellii KMM 231T, isolated from a seawater sample taken at a depth of 4000 m, represents an engaging microorganism to investigate in terms of its cell wall components. Here, we report the structural study of the R-type lipopolysaccharide isolated from I. zobellii KMM 231T that was achieved through a multidisciplinary approach comprising chemical analyses, NMR spectroscopy, and MALDI mass spectrometry. The lipooligosaccharide turned out to be characterized by a novel and unique pentasaccharide skeleton containing a very short mono-phosphorylated core region and comprising terminal neuraminic acid. The lipid A was revealed to be composed of a classical disaccharide backbone decorated by two phosphate groups and acylated by i13:0(3-OH) in amide linkage, i11:0 (3-OH) as primary ester-linked fatty acids, and i11:0 as a secondary acyl chain.

Horizontal transfer and phylogenetic distribution of the immune evasion factor tarP

Methicillin-resistant Staphylococcus aureus (MRSA), a major human pathogen, uses the prophage-encoded tarP gene as an important immune evasion factor. TarP glycosylates wall teichoic acid (WTA) polymers, major S. aureus surface antigens, to impair WTA immunogenicity and impede host defence. However, tarP phages appear to be restricted to only a few MRSA clonal lineages, including clonal complexes (CC) 5 and 398, for unknown reasons. We demonstrate here that tarP-encoding prophages can be mobilized to lysogenize other S. aureus strains. However, transfer is largely restricted to closely related clones. Most of the non-transducible clones encode tarM, which generates a WTA glycosylation pattern distinct from that mediated by TarP. However, tarM does not interfere with infection by tarP phages. Clonal complex-specific Type I restriction-modification systems were the major reasons for resistance to tarP phage infection. Nevertheless, tarP phages were found also in unrelated S. aureus clones indicating that tarP has the potential to spread to distant clonal lineages and contribute to the evolution of new MRSA clones.

Molecular Characterization and Biocompatibility of Exopolysaccharide Produced by Moderately Halophilic Bacterium Virgibacillus dokdonensis from the Saltern of Kumta Coast

The use of natural polysaccharides as biomaterials is gaining importance in tissue engineering due to their inherent biocompatibility. In this direction, the present study aims to explore the structure and biocompatibility of the EPS produced by Virgibacillus dokdonensis VITP14. This marine bacterium produces 17.3 g/L of EPS at 96 h of fermentation. The EPS was purified using ion exchange and gel permeation chromatographic methods. The porous web-like structure and elemental composition (C, O, Na, Mg, P, S) of the EPS were inferred from SEM and EDX analysis. AFM analysis revealed spike-like lumps with a surface roughness of 84.85 nm. The zeta potential value of −10 mV indicates the anionic nature of the EPS. Initial molecular characterization showed that the EPS is a heteropolysaccharide composed of glucose (25.8%), ribose (18.6%), fructose (31.5%), and xylose (24%), which are the monosaccharide units in the HPLC analysis. The FTIR spectrum indicates the presence of functional groups/bonds typical of EPSs (O-H, C-H, C-O-H, C-O, S=O, and P=O). The polymer has an average molecular weight of 555 kDa. Further, NMR analysis revealed the monomer composition, the existence of two α- and six β-glycosidic linkages, and the branched repeating unit as → 1)[α-D-Xylp-(1 → 2)-α-D-Glcp-(1 → 6)-β-D-Glcp-(1 → 5)]-β-D-Frup-(2 → 2)[β-D-Xylp-(1 → 4)]-β-D-Xylp-(1 → 6)-β-D-Fruf-(2 → 4)-β-D-Ribp-(1 →. The EPS is thermally stable till 251.4 °C. X-ray diffraction analysis confirmed the semicrystalline (54.2%) nature of the EPS. Further, the EPS exhibits significant water solubility (76.5%), water-holding capacity (266.8%), emulsifying index (66.8%), hemocompatibility (erythrocyte protection > 87%), and cytocompatibility (cell viability > 80% on RAW264.7 and keratinocyte HaCaT cells) at higher concentrations and prolongs coagulation time in APTT and PT tests. Our research unveils the significant biocompatibility of VITP14 EPS for synthesizing a variety of biomaterials.

An N-linked tetrasaccharide from Halobacterium salinarum presents a novel modification, sulfation of iduronic acid at the O-3 position

Halobacterium salinarum, a halophilic archaeon that grows at near-saturating salt concentrations, provided the first example of N-glycosylation outside Eukarya. Yet, almost 50 years later, numerous aspects of such post-translational protein processing in this microorganism remain to be determined, including the architecture of glycoprotein-bound glycans. In the present report, nuclear magnetic resonance spectroscopy was used to define a tetrasaccharide N-linked to both archaellins, building blocks of the archaeal swimming device (the archaellum), and the S-layer glycoprotein that comprises the protein shell surrounding the Hbt. salinarum cell as β-GlcA(2S)-(1 → 4)-α-IdoA(3S)-(1 → 4)-β-GlcA-(1 → 4)-β-Glc-Asn. The structure of this tetrasaccharide fills gaps remaining from previous studies, including confirmation of the first known inclusion of iduronic acid in an archaeal N-linked glycan. At the same time, the sulfation of this iduronic acid at the O-3 position has not, to the best of our knowledge, been previously seen. As such, this may represent yet another unique facet of N-glycosylation in Archaea.

The Astounding World of Glycans from Giant Viruses

Viruses are a heterogeneous ensemble of entities, all sharing the need for a suitable host to replicate. They are extremely diverse, varying in morphology, size, nature, and complexity of their genomic content. Typically, viruses use host-encoded glycosyltransferases and glycosidases to add and remove sugar residues from their glycoproteins. Thus, the structure of the glycans on the viral proteins have, to date, typically been considered to mimick those of the host. However, the more recently discovered large and giant viruses differ from this paradigm. At least some of these viruses code for an (almost) autonomous glycosylation pathway. These viral genes include those that encode the production of activated sugars, glycosyltransferases, and other enzymes able to manipulate sugars at various levels. This review focuses on large and giant viruses that produce carbohydrate-processing enzymes. A brief description of those harboring these features at the genomic level will be discussed, followed by the achievements reached with regard to the elucidation of the glycan structures, the activity of the proteins able to manipulate sugars, and the organic synthesis of some of these virus-encoded glycans. During this progression, we will also comment on many of the challenging questions on this subject that remain to be addressed.