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At least 253 records · Page 14Linked to original sources
PubMed1990

Anomalous Zemplén deacylation reactions of 2-O-acyl-3-O-alkyl or -3-O-glycosyl derivatives of D-galactose and D-glucose: synthesis of O-alpha-D-mannopyranosyl-(1----4)-O-alpha-L-rhamnopyranosyl-(1----3)-D- galactose and an intermediate for the preparation of 2-O-glycosyl-3-O-(alpha-D-mannopyranosyl)-D-glucoses.

Treatment of 2-O-benzoyl (1) and 2-O-acetyl (5) derivatives of benzyl 4,6-benzylidene-3-O-(2,3,4-tri-O-acetyl-alpha-L-rhamnopyranosyl)-beta-D- galactopyranoside under Zemplén conditions (catalytic amount of sodium methoxide in methanol) gave partially deacylated disaccharides in which the 2-O-acyl groups were retained. Likewise, a similar result was obtained with the beta-L-rhamnopyranosyl analogue (3) of 1. This anomalous reaction was used in a synthesis of the title trisaccharide (17) and of methyl 4,6-O-benzylidene-3-O-(2,3:4,6-di-O-isopropylidene-alpha-D-mannopyranosy l)- alpha-D-glucopyranoside, an intermediate for the synthesis of 2-O-glycosyl-3-O-(alpha-D-mannopyranosyl)-D-glucoses.

Acetylation↗
PubMed1989

Purification of Shiga toxin by alpha-D-galactose-(1----4)-beta-D-galactose-(1----4)-beta-D-glucose-(1- ---) receptor ligand-based chromatography.

A simple and rapid method for Shiga toxin purification based on specific binding to the Gal alpha 1----4Gal beta 1----4Glc globotrioside trisaccharide covalently linked to polyacryl/polyvinyl (Fractogel) has been developed. A cell-free sonicate-filtrate of Shigella dysenteriae type 1, strain 114Sd was passed over the globotrioside-Fractogel column, and bound toxin eluted with 6 M guanidine-HCl. A yield of 36 mg pure toxin/1 sonicate-filtrate was obtained, i.e. a one step 1224-fold purification. The recovery of biologically active toxin was 87%. The toxin was purified to homogeneity as shown by native PAGE and SDS-PAGE.

Animals↗
PubMed1995

Biochemical studies of pig xenoantigens detected by naturally occurring human antibodies and the galactose alpha(1-3)galactose reactive lectin.

The xenotransplantation of pig organs to humans is now receiving serious consideration because of the shortage of human donors for organ transplants. However, such xenografts would be hyperacutely rejected due to naturally occurring antibodies, present in all human sera, that react with pig antigens on the surface of endothelial cells, leading to complement fixation and the rapid onset of intravascular coagulation. A major target of these human natural antibodies is the terminal nonreducing disaccharide Gal alpha (1,3)Gal, and we now report on the array of molecules that are galactosylated by the alpha 1,3-galactosyltransferase. Pig lymphocytes and endothelial cells (both of which bear Gal alpha(1,3)Gal epitopes) were surface iodinated and the 125I-labeled molecules were precipitated with either human antibodies or the lectin from Griffonia simplicifolia (IB4, which binds to Gal alpha(1,3)Gal epitopes). The precipitated molecules were analyzed by gel electrophoresis and autoradiography. Five major groups of molecules were identified by one-dimensional SDS/PAGE (alpha 220 kDa, beta 160-180 kDa, gamma 120 kDa, delta 64 kDa, epsilon 40 kDa); the beta molecule was different in the 2 cell types (beta 1 of lymphocytes and beta 2 of endothelial cells). Two-dimensional SDS/PAGE analysis revealed that each of these groups of molecules resolved into further species of different charge (presumably due to different glycosylation) and also different molecular mass to give at least 20 different Gal alpha(1,3)Gal+ surface molecules. None of these molecules appeared to be present as disulfide-associated dimers. It is clear that there are many galactosylated molecules on the cell surface; indeed, using longer exposures of the autoradiographs, at least 40 different Gal alpha (1,3)Gal+ molecules could be identified. Several of these molecules are likely to have been identified by others, e.g., the 115-kDa, 125-kDa, and 135-kDa triad identified by Platt. Strategies to overcome hyperacute rejection could include modification or deletion of the alpha 1,3-galactosyltransferase gene, which would simultaneously delete all the Gal alpha(1,3)Gal epitopes on these molecules.

Animals↗
PubMed2002

Analysis of the control of the anti-gal immune response in a non-human primate by galactose alpha1-3 galactose trisaccharide-polyethylene glycol conjugate.

BACKGROUND: The current limitation to the clinical application of xenotransplantation using pig organs is a rejection process that has been termed delayed xenograft rejection or acute vascular rejection. It is thought that acute vascular rejection may be mediated at least in part by both the continued synthesis, of preexisting, and the induction, posttransplantation, of antibodies against the carbohydrate moiety galalpha1-3gal that is present on glycoproteins and glycolipids of the pig endothelium. The synthesis of these antibodies has proven difficult to control with currently available immunosuppressive agents. METHODS: We have synthesized galalpha1-3gal conjugated polyethylene glycol polymers that can bind to anti-galalpha1-3gal antibodies and tested their activity in non-human primates. RESULTS: These conjugates when administered to non-human primates can substantially reduce the levels of preexisting and control the induction of anti-galalpha1-3gal antibodies. The level of circulating antibody-secreting cells that make anti-galalpha1-3gal antibodies is also reduced. CONCLUSION: These alpha-gal polyethylene glycol conjugates may have the potential to control the anti-gal antibody response in a pig to primate organ transplant setting and may be a useful therapeutic agent in prolonging graft survival.

Animals↗