Brownian motion of nucleated cell envelopes impedes adhesion

We demonstrate that composite envelopes of nucleated cells exhibit pronounced short wavelength (<= 0.5 mu m) bending excitations of similar to 10 nm root mean square amplitudes at physiological temperatures, which impede strong adhesion due to entropic repulsion forces. Quantitative microinterferometric analysis of the dynamic cell surface roughness of macrophages in terms of the theory of statistical surfaces suggests that the membrane excitations are mainly thermally driven Brownian motions (although active driving forces may contribute substantially). We determine the effective bending modulus of the cell envelope (similar to 1000k(B)T), the cortical tension (similar to 10(-4) N m(-1)), and the work of adhesion (similar to 10(-5) J m(-2)).