We explored the ability of a novel method of nano-scale movement detection to analyze the effects of chemical crosslinking and thiol reduction on the fluctuations of the human erythrocyte membrane. The method employs line images of light intensity distribution across the red blood cell, obtained by laser scanning phase contrast microscope. The essential feature of these images is a noiseless region corresponding to edge scene. This enables- one to carry out very accurate fitting procedure between the theoretical intensity distribution and the experimental one. One of the free parameters of fitting is the edge position. Measuring line scan intensity distributions with a certain sampling rate and defining the edge positions in consequent moments of time, yields the time-dependent displacement of cell's edge with up to nanometer scale precision.

The significant feature of the suggested procedure is that it implicitly takes into account the halo effect.