Characterization of the interactions between various hexadecylmannoside–phospholipid model membranes with the lectin Concanavalin A

Abstract

The specific interaction of Concanavalin A (ConA) with glycolipid-containing model membranes was investigated using (a) surface pressure–time (Π–t) curves, (b) epifluorescence microscopy connected to a film balance, (c) atomic force microscopy (AFM) of the monofilms after Langmuir–Blodgett (LB) transfer and (d) quartz crystal microbalance (QCMB) weight-quantification of the adhered protein on the glycolipid model membrane. The adsorption of ConA on a model membrane was mannose-specific and concentration-dependent in the range 1–50% (1% was the lower detection limit, whereas above 30% saturation began). Adsorption kinetics was followed by QCMB and Π–t measurements. Saturation was reached after 1 h. Hydrophilic spacers were introduced between the alkyl chain and the mannose headgroup of the ConA ligands. The quantity of specific ConA-adhesion increased with spacer length and also the adhesion kinetics was accelerated using protruding ligands. With AFM it was possible to detect morphological differences of mixed hexadecylmannoside–1,2-distearyl-sn-glycero-3-phosphocholine (DSPC) films in dependence on spacer length of the glycolipid before and after molecular contact with ConA.