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

The specific interaction of Concanavalin A (ConA) with glycolipid-containin g model membranes was investigated using (a) surface pressure-time (Pi-t) c urves, (b) epifluorescence microscopy connected to a film balance, (c) atom ic force microscopy (AFM) of the monofilms after Langmuir-Blodgett (LB) tra nsfer and (d) quartz crystal microbalance (QCMB) weight-quantification of t he adhered protein on the glycolipid model membrane. The adsorption of ConA on a model membrane was mannose-specific and concentration-dependent in th e range 1-50% (1% was the lower detection limit, whereas above 30% saturati on began). Adsorption kinetics was followed by QCMB and Pi-t measurements. Saturation was reached after 1 h. Hydrophilic spacers were introduced betwe en the alkyl chain and the mannose headgroup of the ConA ligands. The quant ity of specific ConA-adhesion increased with spacer length and also the adh esion kinetics was accelerated using protruding ligands. With AFM it was po ssible 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.