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Design of a liquid cell toward three-dimensional imaging of unidirectionally-aligned particles in solution using X-ray free-electron lasers

Design of a liquid cell toward three-dimensional imaging of unidirectionally-aligned particles in solution using X-ray free-electron lasers

Phys Chem Chem Phys. 2020 Feb 7;22(5):2622-2628. Epub 2019 Aug 23.
doi: 10.1039/c9cp03658j

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摘要

X-ray free-electron lasers (XFELs) opened up a possibility for molecular-scale single particle imaging (SPI) without the need for crystallization. In SPI experiments, the orientation of each particle has to be determined from the measured diffraction pattern. Preparing unidirectionally-aligned particles can facilitate the determination of the sample orientation. Here, we show the design principles of a liquid cell for three-dimensional imaging of unidirectionally-aligned particles in solution with XFELs. The liquid cell was designed so that neither incident X-rays nor diffracted X-rays are blocked by the substrate of the liquid cell even at high tilt angles. As a feasibility evaluation, we performed coherent diffraction measurements using the cells with a 1 μm focused XFEL beam. We successfully measured coherent diffraction patterns of a nano-fabricated metal pattern at 70° tilt angle and obtained the reconstructed image by applying iterative phase retrieval. The liquid cell will be usefully applied to molecular-scale SPI by using more tightly focused XFELs. In particular, imaging of membrane proteins embedded in lipid membranes is expected to have an enormous impact on life science and medicine.