title: Simultaneous cryo X-ray ptychographic and fluorescence microscopy of green algae.
abstract: Trace metals play important roles in normal and in disease-causing biological functions. X-ray fluorescence microscopy reveals trace elements with no dependence on binding affinities (unlike with visible light fluorophores) and with improved sensitivity relative to electron probes. However, X-ray fluorescence is not very sensitive for showing the light elements that comprise the majority of cellular material. Here we show that X-ray ptychography can be combined with fluorescence to image both cellular structure and trace element distribution in frozen-hydrated cells at cryogenic temperatures, with high structural and chemical fidelity. Ptychographic reconstruction algorithms deliver phase and absorption contrast images at a resolution beyond that of the illuminating lens or beam size. Using 5.2-keV X-rays, we have obtained sub-30-nm resolution structural images and ∼90-nm-resolution fluorescence images of several elements in frozen-hydrated green algae. This combined approach offers a way to study the role of trace elements in their structural context.
authors: Applied Physics, Northwestern University, Evanston, IL 60208;
authors: Junjing
authors: J
authors: Deng
authors: X-ray Science Division, Advanced Photon Source, Argonne National Laboratory, Argonne, IL 60439;
authors: David J
authors: DJ
authors: Vine
authors: X-ray Science Division, Advanced Photon Source, Argonne National Laboratory, Argonne, IL 60439;
authors: Si
authors: S
authors: Chen
authors: Mathematics and Computing Science Division, Argonne National Laboratory, Argonne, IL 60439;
authors: Youssef S G
authors: YS
authors: Nashed
authors: Department of Physics and Astronomy, Northwestern University, Evanston, IL 60208;
authors: Qiaoling
authors: Q
authors: Jin
authors: Australian Research Council, Centre of Excellence for Advanced Molecular Imaging, La Trobe University, Melbourne, VIC 3086, Australia; Australian Research Council, Centre of Excellence for Coherent X-ray Science, La Trobe University, Melbourne, VIC 3086, Australia; Commonwealth Scientific and Industrial Research Organization Manufacturing Flagship, Parkville, VIC 3052, Australia; and.
authors: Nicholas W
authors: NW
authors: Phillips
authors: Mathematics and Computing Science Division, Argonne National Laboratory, Argonne, IL 60439;
authors: Tom
authors: T
authors: Peterka
authors: Mathematics and Computing Science Division, Argonne National Laboratory, Argonne, IL 60439;
authors: Rob
authors: R
authors: Ross
authors: X-ray Science Division, Advanced Photon Source, Argonne National Laboratory, Argonne, IL 60439;
authors: Stefan
authors: S
authors: Vogt
authors: Applied Physics, Northwestern University, Evanston, IL 60208; Department of Physics and Astronomy, Northwestern University, Evanston, IL 60208; Chemistry of Life Processes Institute, Northwestern University, Evanston, IL 60208 cjacobsen@anl.gov.
authors: Chris J
authors: CJ
authors: Jacobsen
mesh_terms: D000460:Chlorophyta / Q000033:anatomy & histology* / Q000166:cytology; D005615:Freezing; D021621:Imaging, Three-Dimensional / Q000379:methods*; D008856:Microscopy, Fluorescence; D014961:X-Ray Diffraction / Q000379:methods*
keywords: X-ray fluorescence microscopy; cryogenic biological samples; ptychography