We employed force-distance measurements, carried out by Atomic Force Microscopy (AFM), to explore the local elastic properties of the membrane-skeleton of human erythrocytes. To calculate the elastic constant of the membrane-skeleton we chose that part of the withdraw region in the force-distance curve which corresponds to the stretching of the membrane-skeleton complex. In order to achieve efficient stretching of the membrane we increased the adhesion of the tip to the membrane by polysine coating of the tip.

Fig. 1 is presents the method of stretching AFM on which our measurements are based, and in Fig.2 one can see the theoretical model of the deformation of a circular plate with fixed boundaries by an external force (AFM probe ) used for recalculating the membrane's bending modulus from the experimental data.

Since we obtained different detachment patterns of tip from the membrane, we set selection criteria for the choice of appropriate curves corresponding to membrane stretching.