Diffraction before destruction

Nanometer-sized biological molecules are difficult to resolve because they are fragile: they come apart when they are imaged with energetic x-rays or electrons. Fortunately, ultra-short x-ray laser pulses billions of times brighter than previous x-ray sources can now illuminate single biomolecules to produce faint but meaningful signals. These signals are then statistically combined to yield structural information. Because these x-ray pulses are so short, they flee from biomolecules before the latter get a chance to move or show damage. This property permits so-called “diffraction before destruction”, where scientists can image unsuspecting and unperturbed nanoscale objects in their native environment.

Hundreds of experimental parameters modify how x-ray free-electron lasers are generated, focused, made to interact with biomolecules, then detected, and analysed. The combinatorial complexity of such imaging experiments is staggering, which makes designing such experiments tricky, tedious and frustratingly uncertain. Dr Duane LOH from the Centre for Bio-imaging Sciences, together with four other groups of scientists from CFEL and the European XFEL (Hamburg, Germany), has created a comprehensive multi-physics framework that realistically simulates for the first time, how specimen damage in single-particle imaging can be mitigated by instrument and algorithm design.

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Reference: Chun Hong Yoon, Mikhail V Yurkov, Evgeny A Schneidmiller, Liubov Samoylova, Alexey Buzmakov, Zoltan Jurek, Beata Ziaja, Robin Santra, N Duane Loh, Thomas Tschentscher, Adrian P Mancuso.

Scientific reports 6, 2016