Experimental strategies for imaging bioparticles with femtosecond hard X-ray pulses

Abstract

This study explores the capabilities of the Coherent X-ray Imaging Instrument at the Linac Coherent Light Source to image small biological samples. The weak signal from small samples puts a significant demand on the experiment. Aerosolized Omono River virus particles of $40 nm in diameter were injected into the submicrometre X-ray focus at a reduced pressure. Diffraction patterns were recorded on two area detectors. The statistical nature of the measurements from many individual particles provided information about the intensity profile of the X-ray beam, phase variations in the wavefront and the size distribution of the injected particles. The results point to a wider than expected size distribution (from $35 to $300 nm in diameter). This is likely to be owing to nonvolatile contaminants from larger droplets during aerosolization and droplet evaporation. The results suggest that the concentration of nonvolatile contaminants and the ratio between the volumes of the initial droplet and the sample particles is critical in such studies. The maximum beam intensity in the focus was found to be 1.9 Â 10 12 photons per mm 2 per pulse. The full-width of the focus at halfmaximum was estimated to be 500 nm (assuming 20% beamline transmission), and this width is larger than expected. Under these conditions, the diffraction signal from a sample-sized particle remained above the average background to a resolution of 4.25 nm. The results suggest that reducing the size of the initial droplets during aerosolization is necessary to bring small particles into the scope of detailed structural studies with X-ray lasers.

Electrospray sample injection for single-particle imaging with X-ray lasers

“…1b) by measuring the size of particles that are formed when injecting sucrose solution 19 . Sizes were measured by Rayleigh scattering microscopy (RSM) 8 and, in addition, by XFEL diffraction 5,12 . The droplets generated with the GDVN span a wide range of diameters (500 to 2000 nm) whereas droplets generated with the ES aerosoliser are smaller, and more monodisperse (100 to 200 nm).…”

“…The sizes of injected sucrose, carboxysome and TBSV particles were determined by fitting the diffraction image of a uniform sphere model to the measured diffraction patterns 12 . Table 2 lists the data sets that were used.…”

“…While this injector has been used for imaging biological particles with diameters between 80 nanometers 10 and 2000 nanometers 6 , imaging smaller particles has proven challenging 11,12 . Particles appeared rounder, larger, and showed a higher level of polydispersity than in solution 11,12,5 It has been suspected that large and polydisperse initial droplets may be the cause for this size and shape mismatch 12 . Non-volatile contaminants are often unavoidable components of the sample solution and the initial droplet size determines how much remains attached to the aerosolised particle after solvent evaporation.…”

Current Status of Single Particle Imaging with X-ray Lasers

“…"Open science, data sharing, software sharing is the future of science", Carly Strasser says [209]. For SPI, this concept has also been accepted and will be extended to a wider range [217][218][219][220]. At the moment, most published data has been uploaded to the Coherent X-ray Imaging Data Bank (CXIDB) [221,222].…”

Experimental 3D coherent diffractive imaging from photon-sparse random projections

“…This scheme of 'diffraction-before-destruction' is routinely used for Serial Femtosecond Crystallography a klaus.giewekemeyer@xfel.eu b present address: SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park (CA) 94025, USA c present address: Deutsches Elektronen-Synchrotron, Notkestrae 85, 22607 Hamburg, Germany d present address: NSLS-II, Brookhaven National Laboratory, P.O. Box 5000, Upton (NY) 11973, USA [3,4] and has been demonstrated for single biological particles as small as 45 nm in diameter [5].…”