Cluster-Glycoside als Bausteine für Selbstanordnende Monoschichten (SAMs) : Glyco-SAMs als Glycocalix-Mimetika
New methods to study carbohydrate-protein interactions like those, that occur between the glycocalyx and the extracellular matrix have been studied. Utilising the high affinity of sulfur to gold, long aliphatic chains with sulfur-termini were synthesised. These building blocks, that finally were successfully immobilised as SAMs on Au(111), could be equipped with biorelevant head groups very flexibly. As such in a convergent sequence linear fucosides and mannosides were synthesised as were the respective trivalent, clustered fucosides and mannosides and a biologically important mannotrioside. Besides symmetric trivalent glycoclusters, an even more sophisticated compound was build up, carrying two identical mannose residues as bio-active units as well as an alkyne terminus in the trivalent dendritic backbone. As to this particular part of the molecule a marker could be attached after SAM formation and bio-testing, using a 1,3-dipolar cycloaddition, this is a versatile option to determine the actual density of represented bio-functions upon the monolayer by fluorescence. To link the sugar unit with the linear spacer segment first classical peptide coupling was established and then the 1,3-dipolar cycloaddition of alkynes and azides according to Huisgen in the copper(I)-catalysed Sharpless modification was launched successfully. With this array of functional molecules at hand, SPR measurements were carried out to check the immobilisation of the synthesised compounds on gold wafers and the interaction with certain lectins.
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