Biomedical subjects
Publications and source records attributed to David Rabuka.
Fucosylated glycoproteins are involved in many cell-cell recognition events and are markers of embryonic and malignant tissue. Here we report a method for rapid profiling of fucosylated glycoproteins from human cells using 6-azido fucose as a metabolic label.
We developed a polymer coating for carbon nanotubes (CNTs) that mimics the mucin glycoprotein coating of mammalian cells. CNTs coated with these mucin mimic polymers have two novel properties: they can bind to carbohydrate receptors, providing a means for biomimetic interactions with cell surfaces, and, importantly, they are rendered nontoxic to cells.
A library of 4,5- and 4,6-linked bivalent aminoglycoside (AMG) antibiotics consisting of neamine and nebramine pharmacophores have been synthesized. We probed the effect of the linker on antibiotic activity with a series of selected synthetic analogues with varied length and substituents. A number of compounds demonstrated in vitro activity against several bacterial strains and showed activity against drug resistant strains of Pseudomonas aeruginosa. Among the compounds prepared, analogues 12a-d were novel 4,6-linked AMGs containing the nebramine pharmacophore. In addition the lead compound OPT-11 possessed an ED(50) of <or=5mg/kg in a Staphylococcus aureus ATCC 29213 mouse protection model.
Glyco-optimization (OPopS) of aminoglycosides has been performed by replacing the existing sugar moiety with a variety of sugar derivatives. Glycosylation of the 6-position of nebramine provided a library of novel 4,6-linked aminoglycosides (AMGs). Among them, compounds 8b,g,i,l, and 8u with 2"-amino, 2",3"-diamino, 2",4"-diamino, 3",4"-diamino, 3"-amino groups, respectively, showed significant antimicrobial activity against Gram-(+) and -(-) bacteria. Several were particularly potent against Pseudomonus aeruginosa with MICs in the 1-2 microg/mL range.
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All six regioisomeric monophosphates of octyl beta-D-galactopyranosyl-(1 --> 4)-2-acetamido-2-deoxy-beta-D-glucopyranoside have been chemically synthesized and characterized by high-resolution 1H, 13C and 31P NMR spectroscopy. Phosphorylation causes characteristic downfield shifts of the nucleus at the substituted site in the 1H and 13C NMR signals and resulted in a unique 31P signal for each compound.
[reaction: see text] The neuraminic acid derivative 5 is readily converted in several steps to the neuraminic acid dimer 12, linked through the hydroxyl of a 5-N-glycolyl group in an alpha-2,5 glycosidic linkage. The sequence is shown to proceed through a spirocyclic intermediate 9 by in situ NMR experiments. Similar derivatives of N-glycolylneuraminic acid (Neu5Gc), including polymers, have been identified from marine sources, including starfish and sea urchins, often as sulfated derivatives and are thought to mediate sperm-egg recognition.
New insight into the importance of carbohydrates in biological systems underscores the need for rapid synthetic and screening procedures for them. Development of an organic synthesis-compatible linker that would attach saccharides to microtiter plates was therefore undertaken to facilitate research in glycobiology. Galactosyllipids containing small, hydrophobic groups at the anomeric position were screened for noncovalent binding to microtiter plates. When the lipid component was a saturated hydrocarbon between 13 and 15 carbons in length, the monosaccharide showed complete retention after aqueous washing and could be utilized in biological assays. This alkyl chain was also successfully employed with more complex oligosaccharides in biological assays. In light of these findings, this method of attachment of oligosaccharides to microtiter plates should be highly efficacious to high-throughput synthesis and analyses of carbohydrates in biological assays.