X-ray nano-diffraction on cytoskeletal networks

The nano-scale structure of cytoskeletal biopolymers as well as sophisticated superstructures determine the versatile cellular shapes and specific mechanical properties. One example is keratin intermediate filaments in epithelial cells, which form thick bundles that can further organize in a crosslinked network. To study the native structure of keratin bundles in whole cells, high-resolution techniques are required, which do at the same time achieve high penetration depths. We employ scanning x-ray diffraction using a nano-focused x-ray beam to study the structure of keratin in freeze-dried eukaryotic cells. By scanning the sample through the beam we obtain x-ray dark-field images with a resolution of the order of the beam size, which clearly show the keratin network. Each individual diffraction pattern is further analyzed to yield insight into the local sample structure, which allows us to determine the local structure orientation. Due to the small beam size we access the structure in a small sample volume without performing the ensemble average over one complete cell. S Online supplementary data available from stacks.iop.org/NJP/14/085013/ mmedia 3 Author to whom any correspondence should be addressed. New Journal of Physics 14 (2012) 085013 1367-2630/12/085013+15$33.00 © IOP Publishing Ltd and Deutsche Physikalische Gesellschaft