Two-stage robotic crystal mounting of protein crystals for X-ray data collection

We present a new microrobotic system for a crystallographic task called protein crystal mounting, which is the transfer of a crystal from its growth solution onto a tool designed to hold it for X-ray data collection. The system operates autonomously using feedback from a camera looking at the workspace through a microscope. Visual tracking is employed to monitor the location of the selected crystal and control a range of actuators for successful extraction. The task is performed in two stages: First, the crystal is taken from its drop into a pipette and is transported into a cryoprotecting liquid. Second, while in the cryoprotector, it is transferred from the pipette onto a tool to be used for data collection. Key features of this approach are the increased robustness of the system and the avoidance of the damaging effect of direct exposure of the crystal to room conditions. This work is part of a larger effort we have directed at the automation of the high-throughput crystallographic pipeline.