title: A Medipix quantum area detector allows rotation electron diffraction data collection from submicrometre three-dimensional protein crystals.
abstract: When protein crystals are submicrometre-sized, X-ray radiation damage precludes conventional diffraction data collection. For crystals that are of the order of 100 nm in size, at best only single-shot diffraction patterns can be collected and rotation data collection has not been possible, irrespective of the diffraction technique used. Here, it is shown that at a very low electron dose (at most 0.1 e(-) Å(-2)), a Medipix2 quantum area detector is sufficiently sensitive to allow the collection of a 30-frame rotation series of 200 keV electron-diffraction data from a single ∼100 nm thick protein crystal. A highly parallel 200 keV electron beam (λ = 0.025 Å) allowed observation of the curvature of the Ewald sphere at low resolution, indicating a combined mosaic spread/beam divergence of at most 0.4°. This result shows that volumes of crystal with low mosaicity can be pinpointed in electron diffraction. It is also shown that strategies and data-analysis software (MOSFLM and SCALA) from X-ray protein crystallography can be used in principle for analysing electron-diffraction data from three-dimensional nanocrystals of proteins.
authors.affiliation: Biophysical Structural Chemistry, Leiden University, Einsteinweg 55, 2333 CC Leiden, The Netherlands.
authors.forename: Igor
authors.initials: I
authors.lastname: Nederlof
authors.forename: Eric
authors.initials: E
authors.lastname: van Genderen
authors.forename: Yao Wang
authors.initials: YW
authors.lastname: Li
authors.forename: Jan Pieter
authors.initials: JP
authors.lastname: Abrahams
mesh_terms: D000465:Algorithms; D018360:Crystallography, X-Ray; D003625:Data Collection; D003627:Data Interpretation, Statistical; D004583:Electrons; D006801:Humans; D008958:Models, Molecular; D009113:Muramidase / Q000737:chemistry*; D053758:Nanoparticles / Q000737:chemistry*; D011487:Protein Conformation; D011856:Radiographic Image Enhancement / Q000295:instrumentation* / Q000379:methods; D012984:Software
chemical_list: D009113:Muramidase
keywords: MOSFLM; Medipix2; electron diffraction; electron microscopy; nanocrystals