Torque-generating malaria-infected red blood cells in an optical trap.

We have used optical tweezers to trap normal and Plasmodiuminfected red blood cells (iRBCs). Two different facets of the behavior of RBCs in infrared light fields emerge from our experiments. Firstly, while the optical field modifies both types of RBCs in the same fashion, by folding the original biconcave disk into a rod-like shape, iRBCs rotate with linearly polarized light whereas normal RBCs do not. Secondly, and in the context of known molecular motors, our measurements indicate that the torque of rotating iRBCs is up to three orders of magnitude larger.