Nanobeam precession-assisted 3D electron diffraction reveals a new polymorph of hen egg-white lysozyme

• Published in: IUCrJ Vol. 6; no. Pt 2; pp. 178 - 188
• Main Authors: Lanza, Arianna, Margheritis, Eleonora, Mugnaioli, Enrico, Cappello, Valentina, Garau, Gianpiero, Gemmi, Mauro
• Format: Journal Article
• Language: English
• Published: England International Union of Crystallography 01-03-2019
• Subjects: Crystal growth; Crystal structure; Crystallization; Crystallography; Crystals; electron crystallography; Electron diffraction; Electrons; Lysozyme; macromolecular crystallography; Mathematical models; Microcrystals; Molecular dynamics; monoclinic lysozyme; nanobeam pressure-assisted electron diffraction; Nanocrystals; Novels; Parameters; Precession; Protein crystal growth; Proteins; Radiation (Physics); radiation damage; Radiation sources; Research Papers; Single crystals; Structural analysis; Unit cell; X-ray diffraction; monoclinic lysozyme; nanobeam pressure-assisted electron diffraction; radiation damage; macromolecular crystallography; electron crystallography
• ISSN: 2052-2525; 2052-2525
• DOI: 10.1107/S2052252518017657

Recent advances in 3D electron diffraction have allowed the structure determination of several model proteins from submicrometric crystals, the unit-cell parameters and structures of which could be immediately validated by known models previously obtained by X-ray crystallography. Here, the first new protein structure determined by 3D electron diffraction data is presented: a previously unobserved polymorph of hen egg-white lysozyme. This form, with unit-cell parameters
= 31.9,
= 54.4,
= 71.8 Å, β = 98.8°, grows as needle-shaped submicrometric crystals simply by vapor diffusion starting from previously reported crystallization conditions. Remarkably, the data were collected using a low-dose stepwise experimental setup consisting of a precession-assisted nanobeam of ∼150 nm, which has never previously been applied for solving protein structures. The crystal structure was additionally validated using X-ray synchrotron-radiation sources by both powder diffraction and single-crystal micro-diffraction. 3D electron diffraction can be used for the structural characterization of submicrometric macromolecular crystals and is able to identify novel protein polymorphs that are hardly visible in conventional X-ray diffraction experiments. Additionally, the analysis, which was performed on both nanocrystals and microcrystals from the same crystallization drop, suggests that an integrated view from 3D electron diffraction and X-ray microfocus diffraction can be applied to obtain insights into the molecular dynamics during protein crystal growth.