IMAGING ADHESION FORCES AND ELASTICITY OF LYSOZYME ADSORBED ON MICA WITH THE ATOMIC-FORCE MICROSCOPE

We have investigated the adsorption of lysozyme molecules on mica subs trates in buffer by atomic force microscopy (AFM). The stability of th e adsorbate is influenced by buffer conditions. At pH 4 single molecul es can be imaged stably, while at pH 6.4 only aggregates of molecules are observed. Maps of the tip-sample interaction were obtained by reco rding laterally resolved force curves. These force curves showed that the adhesion of the tip on the lysozyme is smaller than on the mica. T he intrinsic viscoelastic properties of lysozyme could be calculated b y analyzing these force curves.