ATP-dependent mechanics of red blood cells

Red blood cells are amazingly deformable structures able to re-cover their initial shape even after large deformations as when passing through tight blood capillaries. The reason for this excep-tional property is found in the composition of the membrane and the membrane-cytoskeleton interaction. We investigate the me-chanics and the dynamics of RBCs by a unique noninvasive tech-nique, using weak optical tweezers to measure membrane fluctu-ation amplitudes with!s temporal and sub nm spatial resolution. This enhanced edge detection method allows to span over>4 orders of magnitude in frequency. Hence, we can simultaneously measure red blood cell membrane mechanical properties such as bending modulus " # 2.8 $ 0.3 % 10&19J # 67.6 $ 7.2 kBT, tension ' # 6.5 $ 2.1 % 10&7N/m, and an effective viscosity (eff # 81 $ 3.7 % 10&3 Pa s that suggests unknown dissipative processes. We furthermore show that cell mechanics highly depends on th