Reference-enhanced x-ray single-particle imaging

Abstract

X-ray single particle imaging involves the measurement of a large number of noisy diffraction patterns of isolated objects in random orientations. The missing information about these patterns is then computationally recovered in order to obtain a three-dimensional structure of the particle. While the method has promised to deliver room temperature structures at near-atomic resolution, there have been significant experimental hurdles in collecting data of sufficient quality and quantity to achieve this goal. This paper describes two ways to modify the conventional methodology which significantly ease the experimental challenges, at the cost of additional computational complexity in the reconstruction procedure. Both these methods involve the use of holographic reference objects in close proximity to the sample of interest, whose structure can be described with only a few parameters. A reconstruction algorithm to recover the unknown degrees of freedom is also proposed and tested with toy-model simulations.

3D diffractive imaging of nanoparticle ensembles using an x-ray laser

“…Improvements could be made through optimised focussing for the targeted size distribution [16] or cryogenic injections systems [18] which additionally allow conformational selection [35]. Another approach is to keep using the larger focus and conjugate the particles with gold nanoparticles to assist hitfinding and orientation determination [36]. The effective hit rate can also be increased by using more pulses from the European XFEL (max.…”

3D diffractive imaging of nanoparticle ensembles using an X-ray laser

“…Improvements could be made through optimised focussing for the targeted size distribution [16] or cryogenic injections systems [18] which additionally allow conformational selection [35]. Another approach is to keep using the larger focus and conjugate the particles with gold nanoparticles to assist hitfinding and orientation determination [36].…”

Charge-State Distribution of Aerosolized Nanoparticles

“…6 Careful and controlled sample delivery are key to successful SPI experiments: 7 high-resolution structure reconstruction relies on a very large number of diffraction patterns of isolated, virtually identical particles. 8 Biological macromolecules, like proteins, are intrinsically flexible 9 and their structural integrity can be decreased by Coulomb repulsion between charges. 10 Therefore, excessive charging of injected biomolecules during SPI experiments must be avoided to maintain their native structure.…”

“…The resulting diffraction patterns of the randomly oriented particles are collected and can subsequently be reconstructed into an average 3D volume with nanometer resolution . Careful and controlled sample delivery are key to successful SPI experiments: high-resolution structure reconstruction relies on a very large number of diffraction patterns of isolated, virtually identical particles …”