Figure 1.

Combined x-ray fluorescence and ptychographic imaging of a frozen hydrated Chlamydomonoas reinhardtii alga. The x-ray microscope²⁷ is shown schematically in (a)⁴⁵, where an energy-dispersive detector was used to record x-ray fluorescence and a pixelated area detector was used to record coherent diffraction patterns for ptychographic image reconstruction. The x-ray fluorescence maps of the elements S, P, K, and Ca shown in (b) have a spatial resolution that is consistent with the ~85 nm theoretical Rayleigh resolution of the focused x-ray beam, while the phase contrast ptychographic image (c) shows considerably more detail due to the reconstruction of x-ray scattering at an angle well beyond the numerical aperture of the Fresnel zone plate used. This image shows a single cup-shaped chloroplast (Ch), as well as a number of other organelles: pyrenoid (Py), nucleus (N), starch granule (Sg), and polyphosphate bodies (Ph). We also note the presence of granules (labeled Ca) with high calcium and phosphorus content, but low sulfur and potassium content.