SELF-ASSEMBLED CARBOHYDRATE MONOLAYERS - FORMATION AND SURFACE SELECTIVE MOLECULAR RECOGNITION

The formation of self-assembled monolayers (SAMs) of representative th iocarbohydrate derivatives onto a gold surface has been investigated t o build an artificial carbohydrate scaffold to mimic non-bonded molecu lar recognition phenomena. Three types of carbohydrate SAMs were formu lated from (i) 1-beta-D-thioglucose (1), (ii) 1-beta-D-thioglucose tet raacetate (2), and (iii) 2-mercaptoethyl alpha-D-mannopyranoside (3). Subsequently, each SAM was spectroscopically characterized by reflecti on-absorption infrared spectroscopy (RAIRS). Deprotection of the acyla ted carbohydrate SAM was achieved in situ, indicating that chemical tr ansformation may be performed without disruption of the sulfur-gold bo nd. With the mannose derivative, in which the carbohydrate moiety was separated from the gold surface by the spacer unit -OCH2CH2SH, it was possible to demonstrate that such a carbohydrate SAM was able to inter act selectively with a specific carbohydrate binding protein, i.e., co ncanavalin A (Con A). Exposure of the mannose derived SAM to a solutio n of Con A led to a specific binding interaction as measured by RAIRS and surface plasmon resonance (SPR). In contrast, on exposure of the m annose SAM to the L-fucose-specific lectin tetragonolobus purpureas, n o such binding was observed. These results suggest that highly ordered SAMs of specifically designed carbohydrate derivatives can be formula ted to mimic natural cell surface structures and used to study selecti ve molecular recognition interactions.