Blood cells in action

In experiments and computer simulations, researchers repeatedly deformed red blood cells, let them "wriggle" and then analysed their behaviour. Three tiny spheres hold the cells in place during the process, while the movements of the cell membrane are measured with the help of a fourth sphere. The "wrapper" of the blood cell consists of a lipid double layer and a cytoskeleton; active forces, produced for example by an ion pump, move the membrane (red arrows) and fluids (green arrows) locally in opposite directions. For the first time, and using physical methods, scientists have demonstrated how red blood cells move. There had been real fights between academics over the question of whether these cells are moved by external forces or whether they actively "wriggle". An international team of biophysicists from Münster, Paris and Jülich have now proven that both opinions are correct. Linking physical principles and biological reality, they recognized that fast molecules in the vicinity make the cell membrane of the blood cells wriggle - but that the cells themselves also become active when they have enough reaction time.