3 research outputs found
X‑rays Reveal the Internal Structure of Keratin Bundles in Whole Cells
In recent years, X-ray imaging of
biological cells has emerged
as a complementary alternative to fluorescence and electron microscopy.
Different techniques were established and successfully applied to
macromolecular assemblies and structures in cells. However, while
the resolution is reaching the nanometer scale, the dose is increasing.
It is essential to develop strategies to overcome or reduce radiation
damage. Here we approach this intrinsic problem by combing two different
X-ray techniques, namely ptychography and nanodiffraction, in one
experiment and on the same sample. We acquire low dose ptychography
overview images of whole cells at a resolution of 65 nm. We subsequently
record high-resolution nanodiffraction data from regions of interest.
By comparing images from the two modalities, we can exclude strong
effects of radiation damage on the specimen. From the diffraction
data we retrieve quantitative structural information from intracellular
bundles of keratin intermediate filaments such as a filament radius
of 5 nm, hexagonal geometric arrangement with an interfilament distance
of 14 nm and bundle diameters on the order of 70 nm. Thus, we present
an appealing combined approach to answer a broad range of questions
in soft-matter physics, biophysics and biology
Visualization 1: MHz frame rate hard X-ray phase-contrast imaging using synchrotron radiation
Electric arc ignition Originally published in Optics Express on 12 June 2017 (oe-25-12-13857
Megahertz pulse trains enable multi-hit serial femtosecond crystallography experiments at X-ray free electron lasers
The European X-ray Free Electron Laser (XFEL) and Linac Coherent Light Source (LCLS) II are extremely intense sources of X-rays capable of generating Serial Femtosecond Crystallography (SFX) data at megahertz (MHz) repetition rates. Previous work has shown that it is possible to use consecutive X-ray pulses to collect diffraction patterns from individual crystals. Here, we exploit the MHz pulse structure of the European XFEL to obtain two complete datasets from the same lysozyme crystal, first hit and the second hit, before it exits the beam. The two datasets, separated by <1 µs, yield up to 2.1 Å resolution structures. Comparisons between the two structures reveal no indications of radiation damage or significant changes within the active site, consistent with the calculated dose estimates. This demonstrates MHz SFX can be used as a tool for tracking sub-microsecond structural changes in individual single crystals, a technique we refer to as multi-hit SFX