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Objective: Investigation of serum bile acid profiles in pregnancies complicated by gestational diabetes mellitus (GDM) in a multi‐ethnic cohort of women who are lean or obese. Design: Prospective cohort study. Setting: UK multicentre study. Population: Fasting serum from participants of European or South Asian self‐reported ethnicity from the PRiDE study, between 23 and 31 weeks of gestation. Methods: Bile acids were measured using ultra‐performance liquid chromatography‐tandem mass spectrometry. Log‐transformed data were analysed using linear regression in STATA/IC 15.0. Main outcome measures: Total bile acids (TBAs), C4, fasting glucose and insulin. Results: The TBAs were 1.327‐fold (1.105–1.594) increased with GDM in European women (P = 0.003). Women with GDM had 1.162‐fold (1.002–1.347) increased levels of the BA synthesis marker C4 (P = 0.047). In South Asian women, obesity (but not GDM) increased TBAs 1.522‐fold (1.193–1.942, P = 0.001). Obesity was associated with 1.420‐fold (1.185–1.702) increased primary/secondary BA ratio (P < 0.001) related to 1.355‐fold (1.140–1.611) increased primary BA concentrations (P = 0.001). TBAs were positively correlated with fasting glucose (P = 0.039) in all women, and with insulin (P = 0.001) and the Homeostatic Model Assessment for Insulin Resistance (HOMA‐IR) (P = 0.001) in women with GDM. Conclusions: Serum BA homeostasis in late gestation depends on body mass index and GDM in ethnicity‐specific ways. This suggests ethnicity‐specific aetiologies may contribute to metabolic risk in European and South Asian women, with the relationship between BAs and insulin resistance of greater importance in European women. Further studies into ethnicity‐specific precision medicine for GDM are required. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Cyclodextrins are widely used as carriers of small molecules for drug delivery owing to their remarkable host properties and excellent biocompatibility. However, cyclic oligosaccharides with different sizes and shapes are limited. Cycloglycosylation of ultra‐large bifunctional saccharide precursors is challenging due to the constrained conformational spaces. Herein we report a promoter‐controlled cycloglycosylation approach for the synthesis of cyclic α‐(1→6)‐linked mannosides up to a 32‐mer. Cycloglycosylation of the bifunctional thioglycosides and (Z)‐ynenoates was found to be highly dependent on the promoters. In particular, a sufficient amount of a gold(I) complex played a key role in the proper preorganization of the ultra‐large cyclic transition state, providing a cyclic 32‐mer polymannoside, which represents the largest synthetic cyclic polysaccharide to date. NMR experiments and a computational study revealed that the cyclic 2‐mer, 4‐mer, 8‐mer, 16‐mer, and 32‐mer mannosides adopted different conformational states and shapes. [ABSTRACT FROM AUTHOR]

We investigated two recently synthesized and characterized sialyl derivatives, bearing the Neu5Ac‐α‐(2‐6)‐Gal epitope, as promising binders for Siglec‐7, an inhibitory Siglec mainly found on natural killer cells. A variety of sialoglycan structures can be recognized by Siglec‐7 with implications in the modulation of immune responses. Notably, overexpression of sialylated glycans recognized by Siglec‐7 can be associated with the progression of several tumors, including melanoma and renal cell carcinoma. NOE‐based NMR techniques, including Saturation Transfer Difference and transferred‐NOESY NMR, together with molecular docking and dynamic simulations were combined to shed light on the molecular basis of Siglec‐7 recognition of two conformationally constrained Sialyl‐Tn antigen analogs. We, therefore, identify the ligands epitope mapping and their conformational features and propose 3D models accurately describing the protein‐ligand complexes. We found that the binding site of Siglec‐7 can accommodate both synthetic analogs, with the sialic acid mainly involved in the interaction. Moreover, the flexibility of Siglec‐7 loops allows a preferred accommodation of the more rigid compound bearing a biphenyl moiety at position 9 of the sialic acid that contributed to the interaction to a large extent. Our findings provided insights for developing potential novel high affinity ligands for Siglec‐7 to hinder tumor evasion. [ABSTRACT FROM AUTHOR]

Glucans are major biomaterials on the earth, with α‐(1→4)‐glucans (i. e. amylose) and β‐(1→4)‐glucans (i. e. cellulose) being the most abundant ones, which are relevant to energy storage and structural function, respectively. Interestingly, (1→4)‐glucans with alternate α/β‐linkages, namely herewith amycellulose, have never been disclosed in nature. Here we report a robust glycosylation protocol for the stereoselective construction of the 1,2‐cis‐α‐ and 1,2‐trans‐β‐glucosidic linkages, which employs an optimal combination of glycosyl N‐phenyltrifluoroacetimidates as donors, TMSNTf2 as promoter, CH2Cl2/nitrile or CH2Cl2/THF as solvents. A broad substrate scope has been demonstrated by coupling five imidate donors with eight glycosyl acceptors, in which most of the glycosylations lead to high yield and exclusively 1,2‐cis‐α‐ or 1,2‐trans‐β‐selectivity. Applying this glycosylation protocol and with an iterative manner, the unprecedented α/β‐alternate (1→4)‐glucans up to a 16‐mer have been synthesized. Differently from amylose, that adopts a compact helicoidal arrangement, the synthetic amycellulose features an extended ribbon‐like conformation, comparable to the extended shape of cellulose. [ABSTRACT FROM AUTHOR]

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 SN2 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. [ABSTRACT FROM AUTHOR]

A collective total synthesis of eight diastereoisomers associated with NMR analysis leads to a full stereochemistry assignment of the structurally unique nucleoside antibiotic A‐94964, which features an octuronic acid uridine core decorated with an α‐D‐mannopyranosyl residue and an α‐D‐N‐acylglucosaminopyranosyl residue via a phosphodiester bridge. [ABSTRACT FROM AUTHOR]

The chemical synthesis of a fully sialylated tetraantennary N‐glycan has been achieved for the first time by using the diacetyl strategy, in which NHAc is protected as NAc2 to improve reactivity by preventing intermolecular hydrogen bonds. Another key was the glycosylation to the branched mannose in an ether solvent, which promoted the desired glycosylation by stabilizing the oxocarbenium ion intermediate. Furthermore, high α‐selectivity of these glycosylation reactions was realized by utilizing remote participation. Two asymmetrically deuterium labeled sialyl N‐glycans were also synthesized by the same strategy. The synthesized N‐glycans were used to probe the molecular basis of H1N1 neuraminidase recognition. The asymmetrically deuterated N‐glycans revealed a difference in the recognition of sialic acid on each branch. Meanwhile, the tetraantennary N‐glycan was used to evaluate the effects of multivalency and steric hinderance by forming branching structures. [ABSTRACT FROM AUTHOR]

The general perception of viruses is that they are small in terms of size and genome, and that they hijack the host machinery to glycosylate their capsid. Giant viruses subvert all these concepts: their particles are not small, and their genome is more complex than that of some bacteria. Regarding glycosylation, this concept has been already challenged by the finding that Chloroviruses have an autonomous glycosylation machinery that produces oligosaccharides similar in size to those of small viruses (6–12 units), albeit different in structure compared to the viral counterparts. We report herein that Mimivirus possesses a glycocalyx made of two different polysaccharides, now challenging the concept that all viruses coat their capsids with oligosaccharides of discrete size. This discovery contradicts the paradigm that such macromolecules are absent in viruses, blurring the boundaries between giant viruses and the cellular world and opening new avenues in the field of viral glycobiology. [ABSTRACT FROM AUTHOR]

Alcaligenes faecalis is the predominant Gram‐negative bacterium inhabiting gut‐associated lymphoid tissues, Peyer's patches. We previously reported that an A. faecalis lipopolysaccharide (LPS) acted as a weak agonist for Toll‐like receptor 4 (TLR4)/myeloid differentiation factor‐2 (MD‐2) receptor as well as a potent inducer of IgA without excessive inflammation, thus suggesting that A. faecalis LPS might be used as a safe adjuvant. In this study, we characterized the structure of both the lipooligosaccharide (LOS) and LPS from A. faecalis. We synthesized three lipid A molecules with different degrees of acylation by an efficient route involving the simultaneous introduction of 1‐ and 4′‐phosphates. Hexaacylated A. faecalis lipid A showed moderate agonistic activity towards TLR4‐mediated signaling and the ability to elicit a discrete interleukin‐6 release in human cell lines and mice. It was thus found to be the active principle of the LOS/LPS and a promising vaccine adjuvant candidate. [ABSTRACT FROM AUTHOR]

The lipopolysaccharide (LPS) O‐antigen structure of the plant pathogen Rhizobium radiobacter strain TT9 and its possible role in a plant‐microbe interaction was investigated. The analyses disclosed the presence of two O‐antigens, named Poly1 and Poly2. The repetitive unit of Poly2 constitutes a 4‐α‐l‐rhamnose linked to a 3‐α‐d‐fucose residue. Surprisingly, Poly1 turned out to be a novel type of biopolymer in which the repeating unit is formed by a monosaccharide and an amino‐acid derivative, so that the polymer has alternating glycosidic and amidic bonds joining the two units: 4‐amino‐4‐deoxy‐3‐O‐methyl‐d‐fucose and (2′R,3′R,4′S)‐N‐methyl‐3′,4′‐dihydroxy‐3′‐methyl‐5′‐oxoproline). Differently from the O‐antigens of LPSs from other pathogenic Gram‐negative bacteria, these two O‐antigens do not activate the oxidative burst, an early innate immune response in the model plant Arabidopsis thaliana, explaining at least in part the ability of this R. radiobacter strain to avoid host defenses during a plant infection process. [ABSTRACT FROM AUTHOR]

The core fucose, a major modification of N‐glycans, is implicated in immune regulation, such as the attenuation of the antibody‐dependent cell‐mediated cytotoxicity of antibody drugs and the inhibition of anti‐tumor responses via the promotion of PD‐1 expression on T cells. Although the core fucose regulates many biological processes, no core fucose recognition molecule has been identified in mammals. Herein, we report that Dectin‐1, a known anti‐β‐glucan lectin, recognizes the core fucose on IgG antibodies. A combination of biophysical experiments further suggested that Dectin‐1 recognizes aromatic amino acids adjacent to the N‐terminal asparagine at the glycosylation site as well as the core fucose. Thus, Dectin‐1 appears to be the first lectin‐like molecule involved in the heterovalent and specific recognition of characteristic N‐glycans on antibodies. [ABSTRACT FROM AUTHOR]

Summary: Background: Non‐alcoholic fatty liver disease (NAFLD) has become the most common chronic liver condition. A major current research effort is ongoing to find potential strategies to treat NAFLD‐non‐alcoholic steatohepatitis (NASH), with special attention to the gut microbiota. Multiple animal studies and pilot clinical trials are assessing different gut microbiota modulating strategies such as faecal microbiota transplantation, antibiotics, probiotics, prebiotics and synbiotics. Aim: To review the role of microbiota in NAFLD‐NASH and determine whether pro‐ and prebiotics have potential as treatment Methods: Information was obtained from critically reviewing literature on PubMed on targeting the gut microbiota in NAFLD. Search terms included NAFLD, NASH, non‐alcoholic fatty liver disease, steatohepatitis; combined with microbiome, microbiota, gut bacteria, probiotics and prebiotics. Results: Animal studies and the first emerging studies in humans show promising results for both the common probiotics Lactobacillus, Bifidobacterium and Streptococci as for short chain fatty acid (SCFA) butyrate‐producing bacteria. Also, prebiotics have positive effects on different mechanisms underlying NAFLD‐NASH. Conclusions: The most promising strategies thus far developed to alter the microbiome in NAFLD‐NASH are probiotics and prebiotics. However, pre‐ and probiotic treatment of NAFLD‐NASH is relatively new and still under development. Actual understanding of the involved mechanisms is lacking and changes in the intestinal microbiota composition after treatment are rarely measured. Furthermore, large clinical trials with comparative endpoints are unavailable. Personalised treatment based on metagenomics gut microbiota analysis will probably be part of the future diagnosis and treatment of NAFLD‐NASH. [ABSTRACT FROM AUTHOR]

In their Research Article (e202307851), Peng Xu, Alba Silipo, You Yang et al. present a promoted-controlled cycloglycosylation approach for the synthesis of a series of cyclic mannosides up to a 32-mer. Keywords: Carbohydrates; Conformational Analysis; Cyclic Oligosaccharides; Cycloglycosylation; Glycosylation EN Carbohydrates Conformational Analysis Cyclic Oligosaccharides Cycloglycosylation Glycosylation 1 1 1 10/18/23 20231023 NES 231023 B Cyclic oligosaccharides b such as cyclodextrins are extensively employed as carriers fo drug delivery owing to their remarkable host properties and excellent biocompatibility. Carbohydrates, Conformational Analysis, Cyclic Oligosaccharides, Cycloglycosylation, Glycosylation. [Extracted from the article]

Carbohydrates, Conformational Analysis, Cyclic Oligosaccharides, Cycloglycosylation, Glycosylation Keywords: Carbohydrates; Conformational Analysis; Cyclic Oligosaccharides; Cycloglycosylation; Glycosylation EN Carbohydrates Conformational Analysis Cyclic Oligosaccharides Cycloglycosylation Glycosylation 1 1 1 10/18/23 20231023 NES 231023 B Cyclic oligosaccharides b such as cyclodextrins are extensively employed as carriers fo drug delivery owing to their remarkable host properties and excellent biocompatibility. In their Research Article (e202307851), Peng Xu, Alba Silipo, You Yang et al. present a promoted-controlled cycloglycosylation approach for the synthesis of a series of cyclic mannosides up to a 32-mer. [Extracted from the article]

Abstract: The chemical synthesis of a bisecting N‐acetylglucosamine (GlcNAc)‐containing N‐glycan was achieved by a convergent synthetic route through [4+2] and [6+2] glycosylations. This synthetic route reduced the number of reaction steps, although the key glycosylations were challenging in terms of yields and selectivities owing to steric hindrance at the glycosylation site and a lack of neighboring group participation. The yields of these glycosylations were enhanced by stabilizing the oxocarbenium ion intermediate through ether coordination. Glycosyl donor protecting groups were explored in an effort to realize perfect α selectivity by manipulating remote participation. The simultaneous glycosylations of a tetrasaccharide with two disaccharides was investigated to efficiently construct a bisecting GlcNAc‐containing N‐glycan. [ABSTRACT FROM AUTHOR]

The structural elucidation of lipopolysaccharides (LPSs) from Gram‐negative marine bacteria, along with the assessment of their immunological properties, is a fascinating and active research field. Such studies can aid understanding of adaptation phenomena that occur in the marine environment, but they can also open up new perspectives on the design and development of new immunoregulatory drugs. In this paper, we report the structural characterization of the lipid A component of the LPS isolated from the marine bacterium Cobetia pacifica KMM 3879T, which is characterized by a family of structures differing in their acylation patterns. The structural assignment was achieved through extensive chemical analysis and matrix‐assisted laser desorption/ionization (MALDI) mass spectrometry. Moreover, cellular immunology studies on the LPS highlighted its low immunostimulatory impact, as well as a very interesting and promising inhibitory activity of the toxic effects of Escherichia coli LPS. [ABSTRACT FROM AUTHOR]

Summary: Plant cell surface receptor‐like kinases (RLKs) mediate the signals from microbe‐associated molecular patterns (MAMPs) that induce immune responses. Lipopolysaccharide (LPS), the major constituent of the outer membrane of gram‐negative bacteria, is a common MAMP perceived by animals and plants; however, the plant receptors/co‐receptors are unknown except for LORE, a bulb‐type lectin S‐domain RLK (B‐lectin SD1‐RLK) in Arabidopsis. OsCERK1 is a multifunctional RLK in rice that contains lysin motifs (LysMs) and is essential for the perception of chitin, a fungal MAMP, and peptidoglycan, a bacterial MAMP. Here, we analyzed the relevance of OsCERK1 to LPS perception in rice. Using OsCERK1‐knockout mutants (oscerk1), we evaluated hydrogen peroxide (H2O2) production and gene expression after LPS treatment. We also examined the LPS response in knockout mutants for the B‐lectin SD1‐RLK genes in rice and for all LysM‐protein genes in Arabidopsis. Compared with wild‐type rice cells, LPS responses in oscerk1 cells were mostly diminished. By contrast, rice lines mutated in either of three B‐lectin SD1‐RLK genes and Arabidopsis lines mutated in the LysM‐protein genes responded normally to LPS. From these results, we conclude that OsCERK1 is an LPS receptor/co‐receptor and that the LPS perception systems of rice and Arabidopsis are significantly different. [ABSTRACT FROM AUTHOR]

The importance of the outer membrane and of its main constituent, lipopolysaccharide, in the symbiosis between rhizobia and leguminous host plants has been well studied. Here, the first complete structural characterization of the entire lipopolysaccharide from an O-chain-deficient Bradyrhizobium ORS285 rfaL mutant is achieved by a combination of chemical analysis, NMR spectroscopy, MALDI MS and MS/MS. The lipid A structure is shown to be consistent with previously reported Bradyrhizobium lipid A, that is, a heterogeneous blend of penta- to hepta-acylated species carrying a nonstoichiometric hopanoid unit and possessing very-long-chain fatty acids ranging from 26:0(25-OH) to 32:0(31-OH). The structure of the core oligosaccharide region, fully characterized for the first time here, is revealed to be a nonphosphorylated linear chain with methylated sugar residues, with a heptose residue exclusively present in the outer core region, and with the presence of two singly substituted 3-deoxy- d- manno-oct-2-ulosonic acid (Kdo) residues, one of which is located in the outer core region. The lipid A moiety is linked to the core moiety through an uncommon 4-substituted Kdo unit. [ABSTRACT FROM AUTHOR]

Extremophiles are microorganisms exhibiting the fascinating capability to thrive in habitats that are considered clearly inhospitable. Extreme-loving microorganisms have acquired ever-increasing importance in the biomedical and pharmaceutical fields, with many of their bioactive products having long been used as life-saving drugs. In this context, extremophile Gram-negative bacterial lipopolysaccharides (LPSs) and their analogues offer many promising opportunities for a variety of biomedical and therapeutic applications. The structure-dependent capability to elicit and to modulate host immune responses is surely the most intriguing feature of LPSs in the context of new drug discovery and design. This review offers an overview of the chemical peculiarities of LPSs isolated from extremophile bacteria, providing the most promising results relating to their biological activity. We discuss the pharmacologically important potential of extremophile LPSs as fundamental immunomodulatory compounds from the perspective of drug synthesis and development. [ABSTRACT FROM AUTHOR]

The search for novel lipid A analogues from any biological source that can act as antagonists, displaying inhibitory activity towards the production of pro-inflammatory cytokines, or as immunomodulators in mammals, is a very topical issue. To this aim, the structure and immunological properties of the lipopolysaccharide lipid A from the purple nonsulfur bacterium Rhodopseudomonas palustris strain BisA53 have been determined. This lipid A displays a unique structural feature, with a non-phosphorylated skeleton made up of the tetrasaccharide Man p-α-(1→4)-Glc pN3N-β-1→6-Glc pN3N-α-(1→1)-α-Gal pA, and four primary amide-linked 14:0(3-OH) and, as secondary O-acyl substituents, a 16:0 and the very long-chain fatty acid 26:0(25-OAc), appended on the Glc pN3N units. This lipid A architecture is definitely rare, so far identified only in the genus Bradyrhizobium. Immunological tests on both murine bone-marrow-derived and human monocyte-derived macrophages revealed an extremely low immunostimulant capability of this LPS lipid A. [ABSTRACT FROM AUTHOR]

The unique α-(1→7)-bradyrhizoside linkages are constructed for the first time via judicious choice of the glycosylation partners and conditions, thus tetra- and penta-bradyrhizosides relevant to the peculiar O-antigen of Bradyrhizobium are synthesized, which are shown to adopt the defined right-handed helical conformations and to be unable to induce innate immune responses in plants. [ABSTRACT FROM AUTHOR]

Understanding the dynamics of protein-ligand interactions, which lie at the heart of host-pathogen recognition, represents a crucial step to clarify the molecular determinants implicated in binding events, as well as to optimize the design of new molecules with therapeutic aims. Over the last decade, advances in complementary biophysical and spectroscopic methods permitted us to deeply dissect the fine structural details of biologically relevant molecular recognition processes with high resolution. This Review focuses on the development and use of modern nuclear magnetic resonance (NMR) techniques to dissect binding events. These spectroscopic methods, complementing X-ray crystallography and molecular modeling methodologies, will be taken into account as indispensable tools to provide a complete picture of protein-glycoconjugate binding mechanisms related to biomedicine applications against infectious diseases. [ABSTRACT FROM AUTHOR]

We report the first complete structural characterization of the lipopolysaccharide (LPS) from a cystic fibrosis (CF) clinical isolate of Prevotella denticola (B003V1S1X). Chemical, spectroscopic, and spectrometric analyses revealed a unique rough-type LPS (LOS) structure. The structure has a highly negatively charged heptasaccharide core region containing hexoses, with the first two sugars, 3-deoxy- D- manno-oct-2-ulosonic acid (Kdo) and mannose, highly phosphorylated. Furthermore, the lipid A moiety has the typical structure for the genus Prevotella, and was also highly phosphorylated. [ABSTRACT FROM AUTHOR]

Lipopolysaccharides (LPSs) are virulence factors that are expressed on the cell surface of Gram-negative bacteria. They represent one of the main traits of bacterial virulence. In this paper, we report the primary structure and the conformational features of the O-chain from the lipopolysaccharide (LPS) produced by Burkholderia gladioli pv. cocovenenans, a bacterium often associated with the mucoralean fungus Rhizopus microsporus var. oligosporus, which is traditionally used in food fermentations. With the aim of understanding the organization of bacterial cell-surface components, we isolated and characterized the following O-antigenic portions of the LPS from B. gladioli pv. cocovenenans: [→2)-α-Rha-(1→2)-α-Aco-(1→2)-α-Rha-(1→4)-β-Gal2Me-(1→] n and [→2)-α-Rha-(1→2)-α-Aco-(1→2)-α-Rha-(1→4)-β-Gal-(1→] n. A distinctive feature of the O-chain is the presence of methylated sugar residues. This contributes to the creation of a hydrophobic shield. The experimental data were confirmed by conformational studies, which showed three-dimensional shapes with different packings and extensions. Such features determine the physicochemical properties of the bacterial envelope, and might contribute to the ability to adapt the membrane surface to the host. [ABSTRACT FROM AUTHOR]

N-glycosylation is a fundamental modification of proteins and exists in the three domains of life and in some viruses, including the chloroviruses, for which a new type of core N-glycan is herein described. This N-glycan core structure, common to all chloroviruses, is a pentasaccharide with a b-glucose linked to an asparagine residue which is not located in the typical sequon N-X-T/S. The glucose is linked to a terminal xylose unit and a hyperbranched fucose, which is in turn substituted with a terminal galactose and a second xylose residue. The third position of the fucose unit is always linked to a rhamnose, which is a semiconserved element because its absolute configuration is virus-dependent. Additional decorations occur on this core N-glycan and represent a molecular signature for each chlorovirus. [ABSTRACT FROM AUTHOR]

In many Gram-negative bacteria, lipopolysaccharide (LPS) and its lipid A moiety are pivotal for bacterial survival. Depending on its structure, lipid A carries the toxic properties of the LPS and acts as a potent elicitor of the host innate immune system via the Toll-like receptor 4/myeloid differentiation factor 2 (TLR4/MD-2) receptor complex. It often causes a wide variety of biological effects ranging from a remarkable enhancement of the resistance to the infection to an uncontrolled and massive immune response resulting in sepsis and septic shock. Since the bioactivity of lipid A is strongly influenced by its primary structure, a broad range of chemical syntheses of lipid A derivatives have made an enormous contribution to the characterization of lipid A bioactivity, providing novel pharmacological targets for the development of new biomedical therapies. Here, we describe and discuss the chemical aspects regarding lipid A and its role in innate immunity, from the (bio)synthesis, isolation and characterization to the molecular recognition at the atomic level. [ABSTRACT FROM AUTHOR]

Background & Aims We analysed for the first time whether recipient perioperative serum total cholesterol ( sTC) concentration is associated with liver transplantation outcome. Methods We studied noncholestatic cirrhotics submitted to primary deceased-donor liver transplantation in a prospective group ( n = 140) from Rome and in a validation retrospective cohort ( n = 157) from Udine, Italy. Pre-ischaemia and post-reperfusion cholesterol metabolism gene mRNA was measured by RT-PCR in 74 grafts of the study group. Results At Cox regression analysis, independently from confounders including recipient MELD score, the recipient pre-operative sTC pooled quintiles 2-5, compared with the lowest quintile showed HR (95% CI) and significances for overall graft loss (GL) of 0.215 (0.104-0.444) P < 0.001 in the study group and 0.319 (0.167-0.610) P = 0.001 in the validation cohort. Analysing sTC as a continuous variable, the risk of overall GL for every 10-mg/dl decrease in pre-operative sTC increased by 13% and by 9% in the study group and in the validation cohort respectively. In the study group, independent associations at multivariate analyses were: (a) high graft pre-ischaemia expression of INSIG-1, which indicates hepatocellular cholesterol depletion, with post-reperfusion graft necrosis; (b) GL with inadequate graft post-reperfusion response to cholesterol depletion, shown by a failure to reduce the PCSK9 to LDLR expression ratio; (c) GL with a relative increase of sTC on post-operative day-7, selectively because of the LDL fraction, which indirectly suggests poor cholesterol uptake from blood. Conclusions Low recipient pre-transplant sTC concentration, its post-operative day-7 increase and a genetically determined low graft cholesterol availability predict poor liver transplant outcome. [ABSTRACT FROM AUTHOR]

Colicins are a diverse family of large antibacterial protein toxins, secreted by and active against E scherichia coli and must cross their target cell's outer membrane barrier to kill. To achieve this, most colicins require an abundant porin (e.g. OmpF) plus a low-copy-number, high-affinity, outer membrane protein receptor (e.g. BtuB). Recently, genetic screens have suggested that colicin N ( ColN), which has no high-affinity receptor, targets highly abundant lipopolysaccharide ( LPS) instead. Here we reveal the details of this interaction and demonstrate that the ColN receptor-binding domain ( ColN- R) binds to a specific region of LPS close to the membrane surface. Data from in vitro studies using calorimetry and both liquid- and solid-state NMR reveal the interactions behind the in vivo requirement for a defined oligosaccharide region of LPS. Delipidated LPS ( LPSΔ LIPID) shows weaker binding; and thus full affinity requires the lipid component. The site of LPS binding means that ColN will preferably bind at the interface and thus position itself close to the surface of its translocon component, OmpF. ColN is, currently, unique among colicins in requiring LPS and, combined with previous data, this implies that the ColN translocon is distinct from those of other known colicins. [ABSTRACT FROM AUTHOR]

Background & Aims Environmental and genetic factors contribute to alcoholic cirrhosis onset. In particular, age at exposure to liver stressors has been shown to be important in progression to fibrosis in hepatitis C individuals. However, no definite data on the role of age at onset of at-risk alcohol consumption are available. Moreover, patatin-like phospholipase domain-containing protein 3 ( PNPLA3) I148M (rs738409) variant has been associated with alcoholic cirrhosis, but only in cross-sectional studies. The aim of this study was to investigate the role of age at onset of at-risk alcohol consumption and PNPLA3 I148M variant on alcoholic cirrhosis incidence. Methods A total of 384 at-risk alcohol drinkers were retrospectively examined. The association among age at onset of at-risk alcohol consumption, PNPLA3 I148M variant and cirrhosis incidence was tested. Results A higher incidence of alcoholic cirrhosis was observed in individuals with an older (≥24 years) compared with a younger (<24) age at onset of at-risk alcohol consumption ( P-value < 0.001). Moreover, PNPLA3 148M allele carriers showed an increased incidence of cirrhosis ( P-value < 0.001). Both age at onset of at-risk alcohol consumption and PNPLA3 148M allele were independent risk factors for developing cirrhosis (H.R. (95% C.I.): 2.76 (2.18-3.50), P-value < 0.001; 1.53(1.07-2.19), P-value = 0.021 respectively). The 148M allele was associated with a two-fold increased risk of cirrhosis in individuals with a younger compared with an older age at onset of at-risk alcohol consumption (H.R. (95% C.I.): 3.03(1.53-6.00) vs. 1.61(1.09-2.38). Conclusions Age at onset of at-risk alcohol consumption and PNPLA3 I148M genetic variant are independently associated with alcoholic cirrhosis incidence. [ABSTRACT FROM AUTHOR]

We have defined the complete structure and assessed the biological activity of the lipopolysaccharide (LPS) from Alkalimonas delamerensis, an alkaliphilic bacterium isolated from soda lakes in China and East Africa. The structural determination, which was achieved by the use of chemical, spectroscopic and spectrometric approaches, indicates a novel Rough type lipopolysaccharide that is rich in negatively charged groups in the lipid A inner core region. The proinflammatory activity of the pure lipopolysaccharide has also been defined by testing the LPS as a stimulant in human HEK293 cells, which express the CD14/MD2/TLR4 complex (HEK293-hTLR4), and in bone marrow-derived macrophages. [ABSTRACT FROM AUTHOR]

Herbivory results in an array of physiological changes in the host that are separable from the associated physical damage. We have made the surprising observation that an Arabidopsis line [pdko3) mutated in genes encoding plasmodesmal proteins is defective in some, but not all, of the typical plant responses to herbivory. We tested the responses of plasma transmembrane potential (Vm) depolarization, voltage gated K+ channel activity, cytosolic calcium [Ca2+]cyt and reactive oxygen species (ROS) (H202 and NO) release, shoot-to-root signaling, biosynthesis of the phytohormone jasmonic acid (JA) and the elicitation of volatile organic compounds (VOCs). Following herbivory and the release of factors present in insect oral secretions (including a putative β-galactofuranose polysaccharide), both the pdko3 and wild type (WT) plants showed a increased accumulation of [Ca2+]cyt, NO and H202. In contrast, unlike WT plants, the mutant line showed an almost complete loss of voltage gated K+ channel activity and Vm depolarization, a loss of shoot-induced root-Vm depolarization, a loss of activation and regulation of gene expression of the JA defense pathway, and a much diminished release and altered profile of VOCs. The mutations in genes for plasmodesmal proteins have provided valuable genetic tools for the dissection of the complex spectrum of responses to herbivory and shown us that the responses to herbivory can be separated into a calcium-activated oxidative response and a K+-dependent Vm-activated jasmonate response associated with the release of VOCs. [ABSTRACT FROM AUTHOR]

The study of the interaction of glycoside hydrolases with their substrates is fundamental to diverse applications in medicine, food and feed production, and biomass-resource utilization. Recent molecular modeling of the α-xylosidase CjXyl31A from the soil saprophyte Cellvibrio japonicus, together with protein crystallography and enzyme-kinetic analysis, has suggested that an appended PA14 protein domain, unique among glycoside hydrolase family 31 members, may confer specificity for large oligosaccharide fragments of the ubiquitous plant polysaccharide xyloglucan (J. Larsbrink, A. Izumi, F. M. Ibatullin, A. Nakhai, H. J. Gilbert, G. J. Davies, H. Brumer, Biochem. J. 2011, 436, 567-580). In the present study, a combination of NMR spectroscopic techniques, including saturation transfer difference (STD) and transfer NOE (TR-NOE) spectroscopy, was used to reveal extensive interactions between CjXyl31A active-site variants and xyloglucan hexa- and heptasaccharides. The data specifically indicate that the enzyme recognizes the entire cello-tetraosyl backbone of the substrate and product in positive enzyme subsites and makes further significant interactions with internal pendant α-(1→6)-linked xylosyl units. As such, the present analysis provides an important rationalization of previous kinetic data on CjXyl31A and unique insight into the role of the PA14 domain, which was not otherwise obtainable by protein crystallography. [ABSTRACT FROM AUTHOR]

Mannan-binding lectin (MBL) is a soluble, collagen-like C-type lectin that shows the ability to bind certain N-glycosylated carbohydrates through calcium-dependent CRDs. It is composed of three identical polypeptides that form a helical homotrimer further arranged in octadecameric and larger oligomers with a very complex quaternary structure. Several studies have revealed that this protein modulates the immune response, being able to mediate phagocytosis. Unsuitable for industrial-scale production, due to the costs and the difficulties inherent in its extremely complex quaternary structure, its potential for use in successful anti-infective therapy is limited. To produce better, less expensive therapeutic agents, less complex chimeric fusion proteins with similar ligand recognition and enhanced effector functions have been developed. In a previous study, recombinant human MBL (rhMBL) and three L-ficolin ( L-FCN) variants containing the MBL carbohydrate recognition domain and varying lengths of the collagenous domain with potential clinical application against glycosylated enveloped viruses such as Ebola and Marburg were produced. It was also demonstrated that one of these chimeras - L-FCN/MBL76 - had superior effector activity that appeared to be mediated by greater structural flexibility. In this work we have used an NMR-based approach to study, at the atomic level, the mannose-binding activities both of rhMBL and of the chimeric molecule L-FCN/MBL76. Our findings indicate that the analysis of the binding dynamics of immune effector molecules could be useful for the design and optimization of new therapeutic proteins. [ABSTRACT FROM AUTHOR]

One common mechanism of resistance against antimicrobial peptides in Gram-negative bacteria is the addition of 4-amino-4-deoxy- l-arabinose ( l-Ara4N) to the lipopolysaccharide (LPS) molecule. Burkholderia cenocepacia exhibits extraordinary intrinsic resistance to antimicrobial peptides and other antibiotics. We have previously discovered that unlike other bacteria, B. cenocepacia requires l-Ara4N for viability. Here, we describe the isolation of B. cenocepacia suppressor mutants that remain viable despite the deletion of genes required for l-Ara4N synthesis and transfer to the LPS. The absence of l-Ara4N is the only structural difference in the LPS of the mutants compared with that of the parental strain. The mutants also become highly sensitive to polymyxin B and melittin, two different classes of antimicrobial peptides. The suppressor phenotype resulted from a single amino acid replacement (aspartic acid to histidine) at position 31 of LptG, a protein component of the multi-protein pathway responsible for the export of the LPS molecule from the inner to the outer membrane. We propose that l-Ara4N modification of LPS provides a molecular signature required for LPS export and proper assembly at the outer membrane of B. cenocepacia, and is the most critical determinant for the intrinsic resistance of this bacterium to antimicrobial peptides. [ABSTRACT FROM AUTHOR]