The Galactosamine Residue in Mycobacterial Arabinogalactan Is α‑Linked

Previous studies have demonstrated that cell wall arabinogalactan from mycobacteria possesses a single galactosamine (GalN) residue. This moiety, which is one of the rare natural occurrences of galactosamine lacking an acetyl group on the nitrogen, has been identified as a pendant substituent attached to a highly branched arabinofuranose residue in the arabinan core. However, the stereochemistry by which the GalN residue is linked to the polysaccharide remains unknown. We report here the synthesis of two tetrasaccharides, <b>1</b> and <b>2</b>, consisting of GalN attached through either an α- or β-linkage to a trisaccharide fragment of mycobacterial arabinan. These molecules represent the first synthetic GalN-containing oligosaccharides, and the preparation of both targets was achieved from a single donor species by modulation of the reaction solvent. Comparison of the NMR spectra of <b>1</b> and <b>2</b> with those obtained from a sample derived from the natural glycan revealed that the GalN residue in the polysaccharide is attached via an α-linkage

Identification of a Novel Mycobacterial Arabinosyltransferase Activity Which Adds an Arabinosyl Residue to α‑d‑Mannosyl Residues

The arabinosyltransferases responsible for the biosynthesis of the arabinan domains of two abundant heteropolysaccharides of the cell envelope of all mycobacterial species, lipoarabinomannan and arabinogalactan, are validated drug targets. Using a cell envelope preparation from <i>Mycobacterium smegmatis</i> as the enzyme source and di- and trimannoside synthetic acceptors, we uncovered a previously undetected arabinosyltransferase activity. Thin layer chromatography, GC/MS, and LC/MS/MS analyses of the major enzymatic product are consistent with the transfer of an arabinose residue to the 6 position of the terminal mannosyl residue at the nonreducing end of the acceptors. The newly identified enzymatic activity is resistant to ethambutol and could correspond to the priming arabinosyl transfer reaction that occurs during lipoarabinomannan biosynthesis

Additional file 1: Figure S1. of Improved monitoring of clinical response in Systemic Lupus Erythematosus by longitudinal trend in soluble vascular cell adhesion molecule-1

Showing analysis of ∆sVCAM-1 levels in SLE subgroups. Plots showing correlation of A unadjusted sVCAM-1 and B ∆sVCAM-1 levels with proteinuria levels in individuals with lupus nephritis. Correlation of ∆sVCAM-1 with change in SLE disease activity measured by ∆ECLAM in C SLE individuals with negative dsDNA titres and D normocomplementaemic SLE individuals. (PDF 36 kb

Subgroup analyses to explore source of heterogeneity.

<p>CVD: cardiovascular disease; RR: relative risk; CI: confidence interval;</p><p>SBP: systolic blood pressure; DBP: diastolic blood pressure.</p

Association between prehypertension and the risk of all-cause mortality.

<p>CI: confidence interval.</p

Association between two ranges of prehypertension, low range (a) and high range (b), and the risk of all-cause mortality.

<p>Low range prehypertension: 120–129/80–84 mmHg; high range prehypertension: 130–139/85–89 mmHg. CI: confidence interval.</p

Flow chart of the study selection process.

<p>Flow chart of the study selection process.</p

Conjugation of A and B Blood Group Structures to Silica Microparticles for the Detection of Antigen-Specific B Cells

Silica microparticles were functionalized with A and B blood group carbohydrate antigens (A type I, A type II, B type I, and B type II) to enable the detection and monitoring of ABO antigen-specific B cells. Microparticles were prepared via the Stöber synthesis, labeled with an Alexafluor fluorescent dye, and characterized via TEM and fluorescence microscopy. The silica microparticles were functionalized with (3-aminopropyl)­trimethoxysilane (APTMS), followed by the use of an established fluorenylmethyloxycarbonyl (Fmoc)-protected PEG-based linker. The terminal Fmoc moiety of the PEG-based linker was then deprotected, yielding free amino groups, to which the A and B antigens were coupled. The carbohydrate antigens were synthesized with a <i>p</i>-nitrophenol ester to enable conjugation to the functionalized silica microparticles via an amide bond. The number of free amine groups available for coupling for a given mass of PEG-functionalized silica microparticles was quantified via reaction with Fmoc-glycine. The antigen-functionalized microparticles were then evaluated for their specificity in binding to A and B antigen-reactive B-cells via flow cytometry, and for blocking of naturally occurring antibodies in human serum. Selective binding of the functionalized microparticles to blood group-reactive B cells was observed by flow cytometry and fluorescence microscopy. The modular approach outlined here is applicable to the preparation of silica microparticles containing any carbohydrate antigen and alternative fluorophores or labels. This approach therefore comprises a novel, general platform for screening B cell populations for binding to carbohydrate antigens, including, in this case, the human A and B blood group antigens