An approach to automated acquisition of cryoEM images from lacey carbon grids

An approach to automated acquisition of cryoEM image data from lacey carbon grids using the Leginon program is described. Automated liquid nitrogen top up of the specimen holder dewar was used as a step towards full automation, without operator intervention during the course of data collection. During cryoEM studies of actin labelled with myosin V, we have found it necessary to work with lacey grids rather than Quantifoil or C-flat grids due to interaction of myosin V with the support film. Lacey grids have irregular holes of variable shape and size, in contrast to Quantifoil or C-flat grids which have a regular array of similar circular holes on each grid square. Other laboratories also prefer to work with grids with irregular holes for a variety of reasons. Therefore, it was necessary to develop a different strategy from normal Leginon usage for working with lacey grids for targeting holes for image acquisition and suitable areas for focussing prior to image acquisition. This approach was implemented by using the extensible framework provided by Leginon and by developing a new MSI application within that framework which includes a new Leginon node (for a novel method for finding focus targets).