Coherent X-ray DIFFRACTION IMAGINg of Cyanidioschyzon merolae

Abstract

Coherent X-ray diffraction imaging (CXDI) is a lensless imaging technique for visualizing the structures of noncrystalline particles at a resolution of several tens of nanometers. The targets are particles with dimensions in the sub-micrometer to micrometer range. We carried out CXDI experiments at 66 K to investigate the internal structures of a whole frozen-hydrated cell and a chloroplast of Cyanidioschyzon merolae and a cyanobacteria cell by using coherent X-ray light sources, such as synchrotron and X-ray free-electron laser facilities. Owing to the short wavelength of the X-rays used (0.225 nm), the absorption and multiple scattering of X-rays inside the specimens were negligible. Diffraction patterns from each specimen particle adsorbed onto a thin membrane were collected at resolutions better than 50 μm -1 in reciprocal space. Therefore, structures of specimen particles can be illustrated at a resolution higher than 200 nm in real space. The most probable electron density map was retrieved from each diffraction pattern. Theinternal structures of the specimens are described here, particularly the structural correlation of the chloroplast of C. merolae and the cyanobacteria cell. Based on the experimental results, we discuss the feasibility of CXDI in the structural analyses of biological cells and cellular organelles.