Ricin is a toxic lectin which presents a potential security threat. Its rapid detection is highly desirable. Here we present a colorimetric bioassay based on the aggregation of carbohydrate-stabilised gold nanoparticles which has been used to detect Ricinus communis Agglutinin 120 (RCA(120)) - a ricin surrogate. To achieve a stable and robust sensing system the anchor chain length and the density of the assembled carbohydrates on the gold particle surface has been examined to determine the optimal coverage for maximal aggregation with both RCA(120) and Concanavalin A (Con A) lectins. Gold nanoparticles were stabilised with either a thiolated galactose derivative (9-mercapto-3,6-diaoxaoctyl-beta-d-galactoside) or a thiolated mannose derivative (9-merapto-3,6-dioxaoctyl-alpha-d-mannoside), for RCA(120) and Con A respectively, diluted in each instance with varying ratios of a thiolated triethylene glycol derivative. Aggregation was induced with the respective cognate lectin with the reaction monitored by UV-visible spectrophotometry. The results obtained show that a particle surface with at least 7.5% galactose is required for aggregation with RCA(120) and 6% mannose coverage is required for aggregation with Con A. For each lectin the sensitivity of the assay could be controlled by adjustment of the carbohydrate density on the gold nanoparticles, but with differing results. Maximal aggregation with Con A was achieved with a monolayer consisting of 100% mannose, whereas for RCA(120) maximal aggregation occurred with 70% coverage of galactose. The limit of detection for RCA(120) using the optimally presented galactose-stabilised nanoparticles was 9 nM.

Enzymatic and chemo-enzymatic approaches provide straightforward access to uridine diphospho sugars irrespective of the relative and absolute configuration of the sugar, its ring size and substitution pattern.

The development of glycobiology relies on the sources of particular oligosaccharides in their purest forms. As the isolation of the oligosaccharide structures from natural sources is not a reliable option for providing samples with homogeneity, chemical means become pertinent. The growing demand for diverse oligosaccharide structures has prompted the advancement of chemical strategies to stitch sugar molecules with precise stereo‐ and regioselectivity through the formation of glycosidic bonds. This Review will focus on the key developments towards chemical O‐glycosylations in the current century. Synthesis of novel glycosyl donors and acceptors and their unique activation for successful glycosylation are discussed. This Review concludes with a summary of recent developments and comments on future prospects.

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Solvent-free per-O-acetylation of sugars with stoichiometric acetic anhydride and catalytic iodine proceeds in high yield (90-99%) to give exclusively pyranose products as anomeric mixtures. Without workup, subsequent anomeric substitution employing iodine in the presence of hexamethyldisilane (i.e., TMS-I generated in situ) gives the corresponding glycosyl iodides in 75-95% isolated yield. Alternatively, and without workup, further treatment with dimethyl disulfide or thiol (ethanethiol or thiocresol) gives anomerically pure thioglycosides in more than 75% overall yield.