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Keywords:Gold glyconanoparticles / Carbohydrates / Surface plasmon resonance / UV/Vis spectroscopy / Transmission electron microscopyThe weak binding affinity of monomeric oligosaccharides with carbohydrate-binding proteins are hampering their use in in-vivo and in-vitro bio-assays. Gold glyconanoparticles (GNPs), prepared from synthetic oligosaccharides, have been used to overcome this weak binding affinity. In this paper, a convenient method for the preparation of GNPs from free oligosaccharides is presented. The reductive amination of saccharides with trityl-protected cysteamine, followed by detritylation, afforded cysteamine-extended saccharides that could be used for the preparation of GNPs under reducing conditions in water. The robust chemistry and facile purification of intermediate and final compounds ensure high yields and reproducible results and the, subsequent, preparation of GNPs proceeded smoothly, even with minute quantities

The relatively insensitive surface plasmon resonance (SPR) signal detection of low‐molecular‐mass analytes that bind with weak affinity to a protein—for example, carbohydrate–lectin binding—is hampering the use of biosensors in interaction studies. In this investigation, low‐molecular‐mass carbohydrates have been labeled with an organoplatinum(II) complex of the type [PtCl(NCNR)]. The attachment of this complex increased the SPR response tremendously and allowed the detection of binding events between monosaccharides and lectins at very low analyte concentrations. The platinum atom inside the organoplatinum(II) complex was shown to be essential for the SPR‐signal enhancement. The organoplatinum(II) complex did not influence the specificity of the biological interaction, but both the signal enhancement and the different binding character of labeled compounds when compared with unlabeled ones makes the method unsuitable for the direct calculation of biologically relevant kinetic parameters. However, the labeling procedure is expected to be of high relevance for qualitative binding studies and relative affinity ranking of small molecules (not restricted only to carbohydrates) to receptors, a process of immense interest in pharmaceutical research.

Three-dimensional structures are not available for polysaccharide synthases and only minimal information on the molecular basis for catalysis is known. The Pasteurella multocida hyaluronan synthase (PmHAS) catalyzes the polymerization of the alternating ␤1,3-N-acetylglucosamine-␤1,4-glucuronic acid sugar chain by the sequential addition of single monosaccharides to the non-reducing terminus. Therefore, PmHAS possesses both GlcNAc-transferase and glucuronic acid (GlcUA)-transferase activities. The recombinant Escherichia coli-derived PmHAS enzyme will elongate exogenously supplied hyaluronan chains in vitro with either a single monosaccharide or a long chain depending on the UDP-sugar availability. Competition studies using pairs of acceptors with distinct termini (where one oligosaccharide is a substrate that may be elongated, whereas the other cannot) were performed here; the lack of competition suggests that PmHAS contains at least two distinct acceptor sites. We hypothesize that the size of the acceptor binding pockets of the enzyme corresponds to the size of the smallest high efficiency substrates; thus we tested the relative activity of a series of authentic hyaluronan oligosaccharides and related structural analogs. The GlcUA-transferase site readily elongates (GlcNAcGlcUA) 2 , whereas the GlcNAc-transferase elongates GlcUA-GlcNAc-GlcUA. The minimally sized oligosaccharides, elongated with high efficiency, both contain a trisaccharide with two glucuronic acid residues that enabled the identification of a synthetic, artificial acceptor for the synthase. PmHAS behaves as a fusion of two complete glycosyltransferases, each containing a donor site and an acceptor site, in one polypeptide. Overall, this information advances the knowledge of glycosaminoglycan biosynthesis as well as assists the creation of various therapeutic sugars for medical applications in the future.Glycosaminoglycans, linear chains composed of alternating disaccharide repeats containing a hexosamine, are a class of heteropolysaccharides that includes hyaluronan (HA), 2 heparin, chondroitin, and keratan. These carbohydrates serve essential roles in vertebrates, including as intracellular adhesives, signaling molecules, anticoagulants, and structural elements. Certain pathogenic bacteria take advantage of these versatile molecules to produce extracellular glycosaminoglycan capsules, thus constructing molecular camouflage to avoid host defenses and increase virulence.The bacterial Pasteurella multocida synthases are dual action enzymes that add both sugars of the glycosaminoglycan repeat to the non-reducing terminus of the acceptor oligosaccharides (1). The P. multocida Type A hyaluronan synthase PmHAS and the P. multocida Type F chondroitin synthase PmCS have been amenable to study due to their two active center architectures (2, 3), their ability to polymerize long chains in vitro (4, 5), and their ability to elongate certain exogenously added acceptor oligosaccharides (6). The Escherichia coli K4 chondroitin polymerase KfoC (7) is ϳ60% ide...

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