Charting electron beam-induced lattice reorientation in molecular nanocrystals

High-energy electrons induce sample damage and motion at the nanoscale to fundamentally limit determination of molecular structures by electron diffraction. Using fast event-based electron counting (EBEC) detectors, we characterize electron beam-induced crystal lattice reorientations (BIR) that appear to broadly affect molecular microcrystals. These lattice reorientations are sufficiently large to bring reflections entirely in or out of excitation, occur as early events in the decay of diffracted signal due to radiolytic damage, and coincide with beam-induced migrations of crystal bend contours within the same fluence regime and at the same illuminated location on a crystal. These effects are observed in crystals of biotin, a series of amino acid metal chelates, and a six-residue peptide, suggesting that incident electrons inevitably warp molecular lattices. The precise orientation changes experienced by a given microcrystal are unpredictable, but are measurable by indexing individual diffraction patterns during beam-induced decay. Often, reorientations can tilt a crystal lattice several degrees away from its initial position, and for an especially beam-sensitive Zn(II)-methionine chelate, are associated with dramatic crystal quakes prior to 1 e-/Å2 exposure. As BIR is coincident with the early stages of beam-induced damage, it echoes the beam-induced motion observed in single particle cryoEM. As with motion correction for cryoEM imaging experiments, correction of BIR-induced errors during data processing could improve the accuracy of MicroED data.