Scanning Small-Angle-X-Ray Scattering for Imaging Biological Cells

Scanning small angle X-ray scattering (SAXS) bridges two worlds of X-ray imaging: We use highly focused beams to spatially resolve the different constituents inside biological cells. Additionally, each individual scattering pattern contains a wealth of information about the internal structure on molecular length scales. X-rays provide high resolution due to their small wave length and high penetration power, allowing for imaging of large three-dimensional objects. For these reasons, X-rays have been established as complementary probes for bio-imaging, besides well-established methods like visible light fluorescence microscopy and electron microscopy (EM). Scanning SAXS, in particular, is well suited for systems with some degree of order, such as bundles of parallel filaments, or high-density aggregates [1]. Here, we present scanning SAXS experiments that were performed at dedicated synchrotron beamlines providing a small beam between 100 nm and 2 µm diameter, high flux, high-end pixel detectors and a sample environment suitable for cell samples, e.g. ID13 at the European Synchrotron Radiation Facility (ESRF), P10 at Deutsches Elektronen-Synchrotron (DESY) or cSAXS at Swiss Light Source (SLS). We use X-ray energies between 7 and 15 keV. A schematic of a typical setup is shown in figure 1a. In the following, we will summarize the most important results we recently obtained on different biological systems, such as components of the cytoskeleton and the DNA in the nucleus.