Rhodium-Catalyzed Oxidative Alkenylation of Anisole: Control of Regioselectivity.

We report the conversion of anisoles and olefins to alkenyl anisoles via a transition-metal-catalyzed arene C-H activation and olefin insertion mechanism. The catalyst precursor, [(η-CH)Rh(μ-OAc)], and the in situ oxidant Cu(OPiv) (OPiv = pivalate) convert anisoles and olefins (ethylene or propylene) to alkenyl anisoles. When ethylene is used as the olefin, the // ratio varies between approximately 1:3:1 (selective for 3-methoxystyrene) and 1:5:10 (selective for 4-methoxystyrene).

Inhibition of growth by masarimycin.

Despite renewed interest, development of chemical biology methods to study peptidoglycan metabolism has lagged in comparison to the glycobiology field in general. To address this, a panel of diamides were screened against the Gram-positive bacterium to identify inhibitors of bacterial growth. The screen identified the diamide masarimycin as a bacteriostatic inhibitor of growth with an MIC of 8 µM.

Synthesis of Masarimycin, a Small Molecule Inhibitor of Gram-Positive Bacterial Growth.

Peptidoglycan (PG) in the cell wall of bacteria is a unique macromolecular structure that confers shape, and protection from the surrounding environment. Central to understanding cell growth and division is the knowledge of how PG degradation influences biosynthesis and cell wall assembly. Recently, the metabolic labeling of PG through the introduction of modified sugars or amino acids has been reported.

Trophic upgrading and mobilization of wax esters in microzooplankton.

Heterotrophic protists play pivotal roles in aquatic ecosystems by transferring matter and energy, including lipids, from primary producers to higher trophic predators. Using as a model organism, changes to the non-saponifiable protist lipids were investigated under satiation and starvation conditions. During active feeding on the alga sp.

RNA-Seq reveals a central role for lectin, C1q and von Willebrand factor A domains in the defensive glue of a terrestrial slug.

The tough, hydrogel glue produced by the slug Arion subfuscus achieves impressive performance through metal-based, protein cross-links. The primary sequence of these proteins was determined through transcriptome sequencing and proteome analysis by tandem mass spectrometry. The main proteins that correlate with adhesive function are a group of 11 small, highly abundant lectin-like proteins.

Diamide Inhibitors of the Bacillus subtilis N-Acetylglucosaminidase LytG That Exhibit Antibacterial Activity.

N-Acetylglucosaminidases (GlcNAcases) play an important role in the remodeling and recycling of bacterial peptidoglycan by degrading the polysaccharide backbone. Genetic deletions of autolysins can impair cell division and growth, suggesting an opportunity for using small molecule autolysin inhibitors both as tools for studying the chemical biology of autolysins and also as antibacterial agents. We report here the synthesis and evaluation of a panel of diamides that inhibit the growth of Bacillus subtilis.

Small-molecule inhibitors of the pseudaminic acid biosynthetic pathway: targeting motility as a key bacterial virulence factor.

Helicobacter pylori is motile by means of polar flagella, and this motility has been shown to play a critical role in pathogenicity. The major structural flagellin proteins have been shown to be glycosylated with the nonulosonate sugar, pseudaminic acid (Pse). This glycan is unique to microorganisms, and the process of flagellin glycosylation is required for H.

The effects of fungal volatile organic compounds on bone marrow stromal cells.

Evidence has shown that individuals exposed to indoor toxic molds for extended periods of time have elevated risk of developing numerous respiratory illnesses. It is not clear at the cellular level what impact mold exposure has on the immune system. Herein, we show that 2 fungal volatiles (E)-2-octenal and oct-1-en-3-ol have cytotoxic effects on murine bone marrow stromal cells.

Functional analysis of SleC from Clostridium difficile: an essential lytic transglycosylase involved in spore germination.

Clostridium difficile is the most common cause of enteric disease and presents a major burden on healthcare systems globally due in part to the observed rapid rise in antibiotic resistance. The ability of C. difficile to form endospores is a key feature in the organism's pathogenesis and transmission, and contributes greatly to its resilient nature.

Structural characterization of surface glycans from Clostridium difficile.

Whole-cell high-resolution magic angle spinning (HR-MAS) NMR was employed to survey the surface polysaccharides of a group of clinical and environmental isolates of Clostridium difficile. Results indicated that a highly conserved surface polysaccharide profile among all strains studied. Multiple additional peaks in the anomeric region were also observed which prompted further investigation.

Never take candy from a stranger: the role of the bacterial glycome in host-pathogen interactions.

With the comprehensive study and complete sequencing of the Haemophilus influenzae genome in 1995 came the term 'genomics' and the beginning of the 'omics' era. Since this time, several analogous fields, such as transcriptomics and proteomics, have emerged. While growth and advancement in these fields have increased understanding of microbial virulence, the study of bacterial glycomes is still in its infancy and little is known concerning their role in host-pathogen interactions.

Characterization of lipid-linked oligosaccharides by mass spectrometry.

N- Glycosylation of proteins is recognized as one of the most common post-translational modifications. Until recently it was believed that N-glycosylation occurred exclusively in eukaryotes until the discovery of the general protein glycosylation pathway (Pgl) in Campylobacter jejuni. We have developed a new glycomics strategy based on lectin-affinity capture of lipid-linked oligosaccharides (LLOs) coupled to capillary electrophoresis mass spectrometry.

Analysis of bacterial lipid-linked oligosaccharide intermediates using porous graphitic carbon liquid chromatography-electrospray ionization mass spectrometry: heterogeneity in the polyisoprenyl carrier revealed.

N-glycosylation of proteins is recognized as one of the most common post-translational modifications. It was believed that N-glycosylation occurred exclusively in eukaryotes until the recent discovery of the general protein glycosylation pathway (Pgl) in Campylobacter jejuni, which has similarities to the eukaryotic system and adds proteins en bloc from a lipid carrier to a protein acceptor. In addition to N-linked glycans, a number of pathogenic bacteria such as Pseudomonas aeruginosa and Neisseria species have been shown to O-glycosylate their proteins through polyisoprene-linked intermediates.

Motility and flagellar glycosylation in Clostridium difficile.

In this study, intact flagellin proteins were purified from strains of Clostridium difficile and analyzed using quadrupole time of flight and linear ion trap mass spectrometers. Top-down studies showed the flagellin proteins to have a mass greater than that predicted from the corresponding gene sequence. These top-down studies revealed marker ions characteristic of glycan modifications.

Affinity-capture tandem mass spectrometric characterization of polyprenyl-linked oligosaccharides: tool to study protein N-glycosylation pathways.

N-glycosylation of proteins is recognized as one of the most common post-translational modifications. Until recently it was believed that N-glycosylation occurred exclusively in eukaryotes before the discovery of the general protein glycosylation pathway (Pgl) in Campylobacter jejuni. To date, most techniques to analyze lipid-linked oligosaccharides (LLOs) of these pathways involve the use of radiolabels and chromatographic separation.

Polyisoprenol specificity in the Campylobacter jejuni N-linked glycosylation pathway.

Campylobacter jejuni contains a general N-linked glycosylation pathway in which a heptasaccharide is sequentially assembled onto a polyisoprenyl diphosphate carrier and subsequently transferred to the asparagine side chain of an acceptor protein. The enzymes in the pathway function at a membrane interface and have in common amphiphilic membrane-bound polyisoprenyl-linked substrates. Herein, we examine the potential role of the polyisoprene component of the substrates by investigating the relative substrate efficiencies of polyisoprene-modified analogues in individual steps of the pathway.

Role of Ser216 in the mechanism of action of membrane-bound lytic transglycosylase B: further evidence for substrate-assisted catalysis.

Lytic transglycosylases cleave the beta-(1-->4)-glycosidic bond in the bacterial cell wall heteropolymer peptidoglycan between the N-acetylmuramic acid (MurNAc) and N-acetylglucosamine (GlcNAc) residues with the concomitant formation of a 1,6-anhydromuramoyl residue. Based on sequence alignments, Ser216 in Pseudomonas aeruginosa membrane-bound lytic transglycosylase B (MltB) was targeted for replacement with alanine to delineate its role in the enzyme's mechanism of action. The specific activity of the Ser216-->Ala MltB derivative was less than 12% of that for the wild-type enzyme, while its substrate binding affinity remained virtually unaltered.

Role of arginine residues in the active site of the membrane-bound lytic transglycosylase B from Pseudomonas aeruginosa.

Lytic transglycosylases cleave the beta-(1-->4)-glycosidic bond in the bacterial cell wall heteropolymer peptidoglycan between the N-acetylmuramic acid (MurNAc) and N-acetylglucosamine (GlcNAc) residues with the concomitant formation of a 1,6-anhydromuramoyl residue. On the basis of both sequence alignments with and structural considerations of soluble lytic transglycosylase Slt35 from Escherichia coli, four residues were predicted to be involved in substrate binding at the -1 subsite in the soluble derivative of Pseudomonas aeruginosa membrane-bound lytic transglycosylase MltB. These residues were targeted for site-specific replacement, and the effect on substrate binding and catalysis was determined.

Substrate binding affinity of Pseudomonas aeruginosa membrane-bound lytic transglycosylase B by hydrogen-deuterium exchange MALDI MS.

Lytic transglycosylases cleave the beta-(1-->4)-glycosidic bond in the bacterial cell wall heteropolymer, peptidoglycan, between the N-acetylmuramic acid (MurNAc) and N-acetylglucosamine (GlcNAc) residues with the concomitant formation of a 1,6-anhydromuramoyl residue. With 72% amino acid sequence identity between the enzymes, the theoretical structure of the membrane-bound lytic transglycosylase B (MltB) from Psuedomonas aeruginosa was modeled on the known crystal structure of Escherichia coli Slt35, the soluble derivative of its MltB. Of the twelve residues in Slt35 known to make contacts with peptidoglycan derivatives in Slt35, nine exist in the same position in the P.

The effect of NAG-thiazoline on morphology and surface hydrophobicity of Escherichia coli.

The beta-hexosaminidase inhibitor and structural analog of the putative oxazolium reaction intermediate of lytic transglycosylases, N-acetylglucosamine thiazoline (NAG-thiazoline), was synthesized in 46% overall yield and tested as an inhibitor of Escherichia coli growth. NAG-thiazoline, at concentrations up to 1 mg/ml, was not found to affect the viability of E. coli DH5alpha.