Glycosyl Residues Research Articles

Assembly collapsing versus heterozygosity oversizing: detection of homokaryotic and heterokaryotic Laccaria trichodermophora strains by hybrid genome assembly.

Genome assembly and annotation using short-paired reads is challenging for eukaryotic organisms due to their large size, variable ploidy and large number of repetitive elements. However, the use of single-molecule long reads improves assembly quality (completeness and contiguity), but haplotype duplications still pose assembly challenges. To address the effect of read length on genome assembly quality, gene prediction and annotation, we compared genome assemblers and sequencing technologies with four strains of the ectomycorrhizal fungus Laccaria trichodermophora. By analysing the predicted repertoire of carbohydrate enzymes, we investigated the effects of assembly quality on functional inferences. Libraries were generated using three different sequencing platforms (Illumina Next-Seq, Mi-Seq and PacBio Sequel), and genomes were assembled using single and hybrid assemblies/libraries. Long reads or hybrid assemby resolved the collapsing of repeated regions, but the nuclear heterozygous versions remained unresolved. In dikaryotic fungi, each cell includes two nuclei and each nucleus has differences not only in allelic gene version but also in gene composition and synteny. These heterokaryotic cells produce fragmentation and size overestimation of the genome assembly of each nucleus. Hybrid assembly revealed a wider functional diversity of genomes. Here, several predicted oxidizing activities on glycosyl residues of oligosaccharides and several chitooligosaccharide acetylase activities would have passed unnoticed in short-read assemblies. Also, the size and fragmentation of the genome assembly, in combination with heterozygosity analysis, allowed us to distinguish homokaryotic and heterokaryotic strains isolated from L. trichodermophora fruit bodies.

Taste of common prebiotic oligosaccharides: impact of molecular structure.

Prebiotic oligosaccharides are naturally occurring nondigestible carbohydrates with demonstrated health benefits. They are also a chemically diverse class of nutrients, offering an opportunity to investigate the impact of molecular structure on oligosaccharide taste perception. Accordingly, a relevant question is whether these compounds are detected by the human gustatory system, and if so, whether they elicit sweet or "starchy" taste. Here, in 3 psychophysical experiments, we investigated the taste perception of 3 commercially popular prebiotics [fructooligosaccharides (FOS), galactooligosaccharides (GOS), xylooligosaccharides (XOS)] in highly pure form. Each of these classes of prebiotics differs in the type of glycosyl residue, and position and type of bond between those residues. In experiments I and II, participants were asked to discriminate a total of 9 stimuli [FOS, GOS, XOS; degree of polymerization (DP) of 2, 3, 4] prepared at 75mM in the presence and absence of lactisole, a sweet receptor antagonist. We found that all 9 compounds were detectable (P < 0.05). We also found that GOS and XOS DP 4 were discriminable even with lactisole, suggesting that their detection was not via the canonical sweet receptor. Accordingly, in experiment III, the taste of GOS and XOS DP 4 were directly compared with that of MOS (maltooligosaccharides) DP 4-6, which has been reported to elicit "starchy" taste. We found that GOS and MOS were perceived similarly although narrowly discriminable, while XOS was easily discriminable from both GOS and MOS. The current findings suggest that the molecular structure of oligosaccharides impacts their taste perception in humans.

MS/MS fingerprint comparison between adjacent generations enables substructure identification: Flavonoid glycosides as cases

MS/MS spectrum matching currently serves as a favored means to identify the concerned metabolites attributing to the accessibility of several famous databases. However, the rule that takes the entire structure into account frequently leads to “0 hit” when inquiring MS/MS (usually MS2) spectrum in the databases. Conjugation plays an important role for the high-level structural diversity of metabolites in all organisms, and a given conjugate usually consists of two or more substructures. If MS3 spectra participate in database retrieval, the structural annotation potential of those databases should be dramatically expanded via identifying substructures. Attributing to the ubiquitous distribution pattern, flavonoid glycosides were deployed as the representative family to justify whether the primary fragment ion termed as Y0+, resulted from neutral loss of glycosyl residue(s), generated identical MS3 spectrum with MS2 spectrum of the aglycone cation namely [A+H]+. Because of owning unique ability to measure MS/MS spectrum with the exactly desired exciting energy, linear ion trap chamber of Qtrap-MS was responsible for generating the desired MS3 and MS2 spectra. When taking both m/z and ion intensity features into consideration, the findings included: 1) glycosides sharing identical aglycones produced the same MS3 spectra for Y0+; 2) different MS3 spectra for Y0+ occurred amongst glycosides bearing distinct, even isomeric, aglycones; 3) isomeric aglycones generated different MS2 spectra; and 4) MS3 spectra for Y0+ agreed with MS2 spectra of [A+H]+ when comparing paired glycoside and aglycone. Together, fingerprint comparison between MS3 and MS2 spectra could structurally annotate the substructures and further advance MS/MS spectrum matching towards the identification of, but not limited to, aglycones for flavonoid glycosides.

An N-glycopeptide MS/MS data analysis workflow leveraging two complementary glycoproteomic software tools for more confident identification and assignments.

Complete coverage of all N-glycosylation sites on the SARS-CoV2 spike protein would require the use of multiple proteases in addition to trypsin. Subsequent identification of the resulting glycopeptides by searching against database often introduces assignment errors due to similar mass differences between different permutations of amino acids and glycosyl residues. By manually interpreting the individual MS2 spectra, we report here the common sources of errors in assignment, especially those introduced by the use of chymotrypsin. We show that by applying a stringent threshold of acceptance, erroneous assignment by the commonly used Byonic software can be controlled within 15%, which can be reduced further if only those also confidently identified by a different search engine, pGlyco3, were considered. A representative site-specific N-glycosylation pattern could be constructed based on quantifying only the overlapping subset of N-glycopeptides identified at higher confidence. Applying the two complimentary glycoproteomic software in a concerted data analysis workflow, we found and confirmed that glycosylation at several sites of an unstable Omicron spike protein differed significantly from those of the stable trimeric product of the parental D614G variant.

Mechanisms of interactions in pattern-recognition of common glycostructures across pectin-derived heteropolysaccharides by Toll-like receptor 4

Complex pectin, originating from terrestrial plant cell walls has been attracting research attention as a promising source of a new innate immune modulator. Numerous bioactive polysaccharides associated with pectin are newly reported every year, but the general mechanism of their immunological action remains unclear owing to the complexity and heterogeneity of pectin. Herein, we systematically investigated the interactions in pattern-recognition for common glycostructures of pectic heteropolysaccharides (HPSs) by Toll-like receptors (TLRs). The compositional similarity of glycosyl residues derived from pectic HPS was confirmed by conducting systematic reviews, leading to molecular modeling of representative pectic segments. Via structural investigation, the inner concavity of leucine-rich repeats of TLR4 was predicted to act as a binding motif for carbohydrate recognition, and subsequent simulations predicted the binding modes and conformations. We experimentally demonstrated that pectic HPS exhibits the non-canonical and multivalent binding aspects for TLR4 resulting in receptor activation. Furthermore, we showed that pectic HPSs were selectively clustered with TLR4 during endocytosis, inducing downstream signals to cause phenotypic activation of macrophages. Overall, we have presented a better explanation for the pattern recognition of pectic HPS and further proposed an approach to understand the interaction between complex carbohydrates and proteins.

Carbohydrate esterases involved in deacetylation of food components by the human gut microbiota.

Non-carbohydrate modifications such as acetylations are widespread in food stuffs as well as they play important roles in diverse biological processes. These modifications meet the gut environment and are removed from their carbohydrate substrates by the resident microbiota. Among the most abundant modifications are O-acetylations, contributing to polysaccharides physico-chemical properties such as viscosity and gelling ability, as well as reducing accessibility for glycosyl hydrolases, and thus hindering polysaccharide degradation. Of particular note, O-acetylations increase the overall complexity of a polymer, thus requiring a more advanced degrading machinery for microbes to utilize it. This minireview describes acetylesterases from the gut microbiota that deacetylate various food polysaccharides, either as natural components of food, ingredients, stabilizers of microbial origin, or as part of microbes for food and beverage preparations. These enzymes include members belonging to at least 8 families in the CAZy database, as well as a large number of biochemically characterized esterases that have not been classified yet. Despite different structural folds, most of these acetylesterases have a common acid-base mechanism and belong to the SGNH hydrolase superfamily. We highlight examples of acetylesterases that are highly specific to one substrate and to the position of the acetyl group on the glycosyl residue of the carbohydrate, while other members that have more broad substrate specificity. Current research aimed at unveiling the functions and regioselectivity of acetylesterases will help providing fundamental mechanistic understanding on how dietary components are utilized in the human gut and will aid developing applications of these enzymes to manufacture novel industrial products.

Surface imprinted bio-nanocomposites for affinity separation of a cellular DNA repair protein.

Apurinic/apyrimidinic endonuclease 1 (APE1) is a multifunctional DNA repair protein localized in different subcellular compartments. The mechanisms responsible for the highly regulated subcellular localization and "interactomes" of this protein are not fully understood but have been closely correlated to the posttranslational modifications in different biological context. In this work, we attempted to develop a bio-nanocomposite with antibody-like properties that could capture APE1 from cellular matrices to enable the comprehensive study of this protein. By fixing the template APE1 on the avidin-modified surface of silica-coated magnetic nanoparticles, we first added 3-aminophenylboronic acid to react with the glycosyl residues of avidin, followed by addition of 2-acrylamido-2-methylpropane sulfonic acid as the second functional monomer to perform the first step imprinting reaction. To further enhance the affinity and selectivity of the binding sites, we carried out the second step imprinting reaction with dopamine as the functional monomer. After the polymerization, we modified the nonimprinted sites with methoxypoly (ethylene glycol) amine (mPEG-NH2 ). The resulting molecularly imprinted polymer-based bio-nanocomposite showed high affinity, specificity, and capacity for template APE1. It allowed for the extraction of APE1 from the cell lysates with high recovery and purity. Moreover, the bound protein could be effectively released from the bio-nanocomposite with high activity. The bio-nanocomposite offers a very useful tool for the separation of APE1 from various complex biological samples.

Most of the rhamnogalacturonan-I from cultured Arabidopsis cell walls is covalently linked to arabinogalactan-protein

To characterize a purified rhamnogalacturonan-I (RG-I) containing both RG-I and arabinogalactan-protein (AGP) types of glycosyl residues, an AGP-specific β-1,3-galactanase that can cleave the AG backbone and release the AG sidechain was applied to this material. Carbohydrate analysis and NMR spectroscopy verified that the galactanase-released carbohydrate consists of RG-I covalently attached to the AG sidechain, proving a covalent linkage between RG-I and AGP. Size exclusion chromatography-multiangle light scattering-refractive index detection revealed that the galactanase-released RG-I has an average molecular weight of 41.6 kDa, which, together with the percentage of pectic sugars suggests an RG-I-AGP comprising one AGP covalently linked to two RG-I glycans. Carbohydrate analysis and NMR results of the RG-I-AGP, the galactanase-released glycans, and the RG lyase-released glycans demonstrated that the attached RG-I glycans are decorated with α-1,5-arabinan, β-1,4-galactan, xylose, and 4-O-Me-xylose sidechains. Our measurement suggests that the covalently linked RG-I-AGP is the major component of the traditionally prepared RG-I.

Glycome Profiling and Bioprospecting Potential of the Himalayan Buddhist Handmade Paper of Tawang Region of Arunachal Pradesh.

The paper and pulp industry (PPI) is one of the largest industries that contribute to the growing economy of the world. While wood remains the primary raw material of the PPIs, the demand for paper has also grown alongside the expanding global population, leading to deforestation and ecological imbalance. Wood-based paper production is associated with enormous utilization of water resources and the release of different wastes and untreated sludge that degrades the quality of the environment and makes it unsafe for living creatures. In line with this, the indigenous handmade paper making from the bark of Daphne papyracea, Wall. ex G. Don by the Monpa tribe of Arunachal Pradesh, India is considered as a potential alternative to non-wood fiber. This study discusses the species distribution modeling of D. papyracea, community-based production of the paper, and glycome profiling of the paper by plant cell wall glycan-directed monoclonal antibodies. The algorithms used for ecological and geographical modeling indicated the maximum predictive distribution of the plant toward the western parts of Arunachal Pradesh. It was also found that the suitable distribution of D. papyracea was largely affected by the precipitation and temperature variables. Plant cell walls are primarily made up of cellulose, hemicellulose, lignin, pectin, and glycoproteins. Non-cellulosic cell wall glycans contribute significantly to various physical properties such as density, crystallinity, and tensile strength of plant cell walls. Therefore, a detailed analysis of non-cellulosic cell wall glycan through glycome profiling and glycosyl residue composition analysis is important for the polymeric composition and commercial processing of D. papyracea paper. ELISA-based glycome profiling results demonstrated that major classes of cell wall glycans such as xylan, arabinogalactans, and rhamnogalacturonan-I were present on D. papyracea paper. The presence of these polymers in the Himalayan Buddhist handmade paper of Arunachal Pradesh is correlated with its high tensile strength. The results of this study imply that non-cellulosic cell wall glycans are required for the production of high-quality paper. To summarize, immediate action is required to strengthen the centuries-old practice of handmade paper, which can be achieved through education, workshops, technical know-how, and effective marketing aid to entrepreneurs.

Structural Characterization and Anti-breast Cancer Activity in vitro of a Novel Polysaccharide From Cymbopogon citratus.

Cymbopogon citratus is an important functional food, widely used for flavoring in Africa and South America. In this study, a novel high-molecular-weight polysaccharide (CCP) from C. citratus was extracted, and its structural characteristics and anti-breast cancer activity in vitro were investigated. CCP contained both α and β configurations and mainly composed of galactose (36.89%), arabinose (23.97%), glucose (18.35%) and rhamnose (9.36%) with an average molecular weight of 1.98 × 106 Da. The main glycosyl residues of CCP detected by methylation analysis were 1,3,6-linked Galp, 1,3-linked Glcp, 1,5-linked Araf , T-Araf , and T-Rhap. In vitro experiments suggested that CCP significantly inhibited the proliferation of MDA-MB-231 cells, decreased the expressions of cyclin D1 and CDK4 and stocked cells at G0/G1 phase. Meanwhile, the typical morphological features of apoptotic cells were also observed. Combining with the consequences of Annexin V-FITC/PI staining, Hoechst 33258 staining and western blot analysis, CCP induced apoptosis of MDA-MB-231 cells by triggering the Fas/FasL-mediated death receptor pathway. Overall, these results provide a theoretical basis for the application of C. citratus polysaccharide as a potential anti-breast cancer agent in functional food and medicine.

Structure analysis and Pb2+-resistant activity of novel oligosaccharide from Trichoderma asperellum

This study was to investigate the structure and activity of extracellular carbohydrate from Trichoderma asperellum. First, the carbohydrate termed TES was extracted from Trichoderma asperellum fermentation broth through the water extraction method. And the extracted carbohydrate were separated and purified by Sephadex G-15 column to produce only one oligosaccharides fraction termed TES–I. Afterward the structural feature of TES–I was investigated by a complication of chemical and instrumental analysis. The average molecular weight of TES–I was 312 Da, and it was mainly composed of arabinose and glucose in the mole ratios of 1:1.0382. The result showed that TES–I was a disaccharide, and the glycosyl residues of TES–I were mainly composed of Glucose (4→1) Arabinose. The experimental results showed that TES–I could adsorb 63.46 % of Pb2+ in sewage, indicating that TES–I has the activity of adsorbing Pb2+. With the preferable absorption capacity, TES–I was considered to have good prospects in bioremediation.

Selective xyloglucan oligosaccharide hydrolysis by a GH31 α-xylosidase from Escherichia coli

Xyloglucan is ubiquitous in the cell walls of land plants and is also an essential storage polymer in seeds of many species. We studied the hydrolysis of the non-reducing end xylosyl residue of xyloglucan oligosaccharides (XGOs) by the Escherichia coli α-xylosidase (YicI). Electrospray Ionization Tandem Mass Spectrometry (ESI-MS/MS) and ion fragmentation analysis together with high performance anion exchange chromatography with pulsed amperometric detection revealed that YicI preferentially removes the xylosyl residue from the glycosyl residue of non-galactosylated oligosaccharides. The YicI shows decreasing activity against the galactosylated oligosaccharides XXXG>XXLG≥XLXG. Studies of the XGOs interaction with active site residues by molecular dynamics simulations suggested that hydrogen bond interactions between the D49 and galactosylated oligosaccharides play an important role in enzyme-XGO interactions. This was confirmed by site-directed mutagenesis, where the D49A mutant affected catalytic efficiency against galactosylated XGOs. Our findings advance xyloglucan disassembly models and highlight the importance of YicI for biotechnology applications.

Characterization of a fluorescent glucose derivative 1-NBDG and its application in the identification of natural SGLT1/2 inhibitors.

Glucose is an important energy source for cells. Glucose transport is mediated by two types of glucose transporters: the active sodium-coupled glucose cotransporters (SGLTs), and the passive glucose transporters (GLUTs). Development of an easy way to detect glucose uptake by the cell can be valuable for research. 1-(N-(7-Nitrobenz-2-oxa-1,3-diazol-4-yl) amino)-1-deoxy-d-glucose (1-NBDG) is a newly synthesized fluorescent glucose analogue. Unlike 2-NBDG, which is a good substrate of GLUTs but not SGLTs, 1-NBDG can be transported by both GLUTs and SGLTs. Thus, 1-NBDG is useful for the screening of SGLT1 and SGLT2 inhibitors. Here we further characterized 1-NBDG and compared it with 2-NBDG. The fluorescence of both 1-NBDG and 2-NBDG was quenched under alkaline conditions, but only 1-NBDG fluorescence could be restored upon neutralization. HPLC analysis revealed that 2-NBDG was decomposed leading to loss of fluorescence, whereas 1-NBDG remained intact in a NaOH solution. Thus, after cellular uptake, 1-NBDG fluorescence can be detected on a plate reader simply by cell lysis in a NaOH solution followed by neutralization with an HCl solution. The fluorescence stability of 1-NBDG was stable for up to 5 h once cells were lysed; however, similar to 2-NBDG, intracellular 1-NBDG was not stable and the fluorescence diminished substantially within one hour. 1-NBDG uptake could also be detected at the single cell level and inhibition of 1-NBDG uptake by SGLT inhibitors could be detected by flow cytometry. Furthermore, 1-NBDG was successfully used in a high-throughput cell-based method to screen for potential SGLT1 and SGLT2 inhibitors. The SGLT inhibitory activities of 67 flavonoids and flavonoid glycosides purified from plants were evaluated and several selective SGLT1, selective SGLT2, as well as dual SGLT1/2 inhibitors were identified. Structure-activity relationship analysis revealed that glycosyl residues were crucial since the aglycon showed no SGLT inhibitory activities. In addition, the sugar inter-linkage and their substitution positions to the aglycon affected not only the inhibitory activities but also the selectivity toward SGLT1 and SGLT2.

Fine Carbohydrate Structure of Dietary Resistant Glucans Governs the Structure and Function of Human Gut Microbiota.

Increased dietary fiber consumption has been shown to increase human gut microbial diversity, but the mechanisms driving this effect remain unclear. One possible explanation is that microbes are able to divide metabolic labor in consumption of complex carbohydrates, which are composed of diverse glycosidic linkages that require specific cognate enzymes for degradation. However, as naturally derived fibers vary in both sugar composition and linkage structure, it is challenging to separate out the impact of each of these variables. We hypothesized that fine differences in carbohydrate linkage structure would govern microbial community structure and function independently of variation in glycosyl residue composition. To test this hypothesis, we fermented commercially available soluble resistant glucans, which are uniformly composed of glucose linked in different structural arrangements, in vitro with fecal inocula from each of three individuals. We measured metabolic outputs (pH, gas, and short-chain fatty acid production) and community structure via 16S rRNA amplicon sequencing. We determined that community metabolic outputs from identical glucans were highly individual, emerging from divergent initial microbiome structures. However, specific operational taxonomic units (OTUs) responded similarly in growth responses across individuals’ microbiota, though in context-dependent ways; these data suggested that certain taxa were more efficient in competing for some structures than others. Together, these data support the hypothesis that variation in linkage structure, independent of sugar composition, governs compositional and functional responses of microbiota.

Protocols for isolating and characterizing polysaccharides from plant cell walls: a case study using rhamnogalacturonan-II

BackgroundIn plants, a large diversity of polysaccharides comprise the cell wall. Each major type of plant cell wall polysaccharide, including cellulose, hemicellulose, and pectin, has distinct structures and functions that contribute to wall mechanics and influence plant morphogenesis. In recent years, pectin valorization has attracted much attention due to its expanding roles in biomass deconstruction, food and material science, and environmental remediation. However, pectin utilization has been limited by our incomplete knowledge of its structure. Herein, we present a workflow of principles relevant for the characterization of polysaccharide primary structure using nature’s most complex polysaccharide, rhamnogalacturonan-II (RG-II), as a model.ResultsWe outline how to isolate RG-II from celery and duckweed cell walls and from red wine using chemical or enzymatic treatments coupled with size-exclusion chromatography. From there, we applied mass spectrometry (MS)-based techniques to determine the glycosyl residue and linkage compositions of the intact RG-II and derived oligosaccharides including special considerations for labile monosaccharides. In doing so, we demonstrated that in the duckweed Wolffiella repanda the arabinopyranosyl (Arap) residue of side chain B is substituted at O-2 with rhamnose. We used electrospray-MS techniques to identify non-glycosyl modifications including methyl-ethers, methyl-esters, and acetyl-esters on RG-II-derived oligosaccharides. We then showed the utility of proton nuclear magnetic resonance spectroscopy (1H-NMR) to investigate the structure of intact RG-II and to complement the RG-II dimerization studies performed using size-exclusion chromatography.ConclusionsThe complexity of pectic polysaccharide structures has hampered efforts aimed at their valorization. In this work, we used RG-II as a model to demonstrate the steps necessary to isolate and characterize polysaccharides using chromatographic, MS, and NMR techniques. The principles can be applied to the characterization of other saccharide structures and will help inform researchers on how saccharide structure relates to functional properties in the future.

The Exostosin Immunohistochemical Status Differentiates Lupus Membranous Nephropathy Subsets With Different Outcomes

The Exostosin Immunohistochemical Status Differentiates Lupus Membranous Nephropathy Subsets With Different Outcomes

UDP-Glycosyltransferases from the UGT344 Family Are Involved in Sulfoxaflor Resistance in Aphis gossypii Glover.

Simple SummaryThe cotton aphid, Aphis gossypii Glover, is a notorious pest in cotton and cucurbit fields. The control of A. gossypii has typically relied on the application of chemical insecticides. Sulfoxaflor is the first commercially available sulfoximine insecticide, which exhibits great efficacy against sap-feeding insect pests and has been applied as an alternative insecticide for controlling of A. gossypii in China. Consequently, A. gossypii quickly developed resistance to this insecticide. Hence, in this study, to clarify the potential detoxifying roles of UGTs (one of the phase II detoxification enzymes) in resistance of A. gossypii against sulfoxaflor, the synergistic effects of two synergists (sulfinpyrazone and 5-nitrouracil) against sulfoxaflor were investigated using the susceptible and laboratory-established sulfoxaflor resistant strain (SulR), and the expression levels of 15 UGT genes were determined by qRT-PCR. Furthermore, the involvement of highly upregulated UGTs in sulfoxaflor-resistant strain was functionally tested by RNA interference (RNAi). Our results suggest that overexpression of UGTs contributes to sulfoxaflor resistance in A. gossypii, which should be useful for understanding sulfoxaflor resistance mechanisms.UDP-glycosyltransferases (UGTs) are major phase II detoxification enzymes that catalyze the transfer of glycosyl residues from activated nucleotide sugars to acceptor hydrophobic molecules and play very important roles in the biotransformation of various endogenous and exogenous compounds. Our previous studies demonstrated that UGTs participated in the detoxification of insecticides in Aphis gossypii. However, the potential roles of UGTs in A. gossypii resistance to sulfoxaflor are still unclear. In this study, two inhibitors of UGT enzymes, sulfinpyrazone and 5-nitrouracil, significantly increased the toxicity of sulfoxaflor to a resistant strain of A. gossypii, whereas there were no synergistic effects in the susceptible strain. Based on the transcriptome sequencing results, the expression levels of 15 UGTs were analyzed by quantitative real-time PCR, and we found that seven UGT genes were highly over-expressed in a sulfoxaflor-resistant strain compared to the susceptible strain, including UGT344B4, UGT344C5, UGT344A11, UGT344A14, and UGT344L2. Further suppressing the expression of UGT344B4, UGT344C5, and UGT344A11 by RNA interference significantly increased the sensitivity of resistant aphids to sulfoxaflor, indicating that the overexpression of UGT genes is potentially associated with sulfoxaflor resistance. These results could provide valuable information for further understanding the mechanisms of insecticide resistance.

Structure of the polysaccharide sheath from the B race of the green microalga Botryococcus braunii

The green microalga Botryococcus braunii forms a colony of cells held together by an intricate extracellular matrix. This extracellular matrix also acts as a storage location for liquid hydrocarbons initially produced inside the cells. These hydrocarbons can be used as feedstocks to produce transportation fuels. In the B race of B. braunii, the extracellular matrix is composed of several elements: a cross-linked hydrocarbon network filled with the liquid hydrocarbons, a retaining wall to hold the hydrocarbons in the extracellular matrix, an arabinogalactan polysaccharide fibrillar sheath that extends outward from the retaining wall, and a single protein known as polysaccharide associated protein is found at the base of the polysaccharide fibers where they connect to the retaining wall. During growth, colonies of the B race of B. braunii shed fragments of the retaining wall with polysaccharide fibrils attached into the media. Here we describe the isolation and structural analysis of these polysaccharides using a series of chemical degradations in combination with glycosyl residue composition and linkage analysis, as well as 2-dimensional nuclear magnetic resonance spectroscopy. The results demonstrate that the polysaccharide is highly branched, consisting of a galactan backbone with short branches comprised of d-galactopyranose, l-arabinofuranose, 4-O-methyl-d-glucopyranuronic acid, and 6-deoxy-d-altropyranose. To our knowledge, this is the first description of 6-deoxyaltrose in algae or plants.

Recent Advances in Glycosidase Probes Used in Escherichia Coli Detection

Pathogenic Escherichia coli poses a serious threat to global public health and is especially dangerous with the increase of antibiotic resistance. β-Glucuronidase (GUS) and some other glycosidases can serve as useful biomarkers or indicators for the detection of E. coli. The probes made up of a glycosyl residue (recognition group), a label or reporter group, and a linkage that is generally a direct glycosidic bond, are powerful analytical tools. Upon hydrolysis of the glycosidic linkages by the corresponding glycosidases, these probes irreversibly release detectable labels or reporter molecules. A variety of such glycosidase probes have been developed and applied for the detection of E. coli or the development of various corresponding detection methods. This paper provides an overview of recent advances in this field, covering the development and applications of chromogenic, fluorogenic, luminogenic, and electrochemical glycosidase substrates. The challenges and opportunities in the probe development for detection of E. coli are also discussed.

Effects and Mechanisms of Acylated Flavonoid on Cancer Chemopreventive Activity

Many studies have shown that flavonoids have various physiological activities such as anti-inflammatory, antibacterial, anti-cancer, and hepatoprotective activities. Meanwhile, its hydrophilic nature has led to low absorption into the body and the limitations of its bioactivity. Many acylated flavonoids and their bioactivities, including those obtained as natural compounds and those synthesized biochemically or chemically, have been reported to improve their bioavailability. This review focuses on the recent developments of the cancer chemopreventive activity of acylated flavonoids. Novel acylated flavonoids have been identified from nature since 2015, and many of them have shown high cytoprotective and anti-inflammatory effects by acylation of glycosyl residues. A large number of acylated flavonoids have been synthesized by enzyme-catalyzed and chemical methods, and their bioactivity has been evaluated. The introduction of acyl groups in the sugar residues showed higher antioxidant activity with increased lipophilicity and improved anti-inflammatory and cytoprotective effects and the ability of apoptosis induction in cancer cells. In contrast, introducing acyl groups into the hydroxy groups of aglycones resulted in less antioxidant activity but improved cancer proliferation inhibition and anti-inflammatory effects. Acylation of flavonoids tends to increase their bioactivity over the parent compound. The increased bioactivity by acylation can be attributed to increased lipophilicity and improved membrane permeability. Acylated flavonoids are one of a group of promising compounds that have cancer chemopreventive effects. However, the study of ADME (Absorption, Distribution, Metabolism, Excretion) will be essential to elucidate the relationship between acylation of flavonoids and the improvement of their bioactivity.