STRUCTURAL TRANSITIONS OF CONCANAVALIN-A ADSORBED ONTO BARE MICA PLATES - SURFACE FORCE MEASUREMENTS

The structure of the beta-sheet rich molecule, concanavalin A (Con A), shows complicated behaviour when mechanical stress is imposed on adsorbed Con A layers. In the pH range 3.9 to 7.4, the structural changes are dependent on the pH and ionic strength of the solution at the liquid/solid interface. Several molecular shapes are observed ranging from a highly unfolded state characterized by a 1.25 nm thickness of each expelled layer at pH 3.9 to other states with various layer thicknesses at pH 6-7.4 and at a low ionic strength (< 10(-4)). In the pH range 6 to 7.4, different molecular species appear to be present.