Cilia and flagella drive the movement of many organisms from protozoa to jellyfish. The link between molecules and biomechanics remains enigmatic. Mathematical models can explain how a flagellum should beat, however, we still lack conclusive experimental proof. Why would we want to know? Many human hereditary diseases are ciliopathies.
African trypanosomes continuously swim and thereby generate directional flow fields on their cell surface. These flow forces become functional when the surface coat, which is dominated by variant surface glycoproteins (VSG), is attacked by host immunoglobulins. Antibody-VSG complexes are caught by hydrodynamic forces and dragged towards the rear of the cell, where they are endocytosed. This means that pure physical forces can sort proteins in the plane of the plasma membrane. The schematic drawing depicts rapid redistribution and endocytosis of antibody (green) bound to VSG (grey).