Abstract
Automation of the mounting of cryocooled samples is now a feature of the majority of beamlines dedicated to macromolecular crystallography (MX). Robotic sample changers have been developed over many years, with the latest designs increasing capacity, reliability and speed. Here, the development of a new sample changer deployed at the ESRF beamline MASSIF-1 (ID30A-1), based on an industrial six-axis robot, is described. The device, named RoboDiff, includes a high-capacity dewar, acts as both a sample changer and a high-accuracy goniometer, and has been designed for completely unattended sample mounting and diffraction data collection. This aim has been achieved using a high level of diagnostics at all steps of the process from mounting and characterization to data collection. The RoboDiff has been in service on the fully automated endstation MASSIF-1 at the ESRF since September 2014 and, at the time of writing, has processed more than 20 000 samples completely automatically.
Highlights
The automation of macromolecular crystallography (MX) experiments on synchrotron beamlines is aimed at increasing throughput and at simplifying data-collection and beamalignment protocols in what can be a complicated and stressful environment for novice users
It is the result of the blending of a wide variety of different software developments including graphical user interfaces (GUIs) for beamline control (Gabadinho et al, 2010; McPhillips et al, 2002; Stepanov et al, 2011; Fodje et al, 2012), online data analysis (Dauter, 1999; Holton & Alber, 2004; Incardona et al, 2009; Leslie et al, 2002; Sauter et al, 2004) and laboratory information-management systems (LIMS; Delageniere et al, 2011; Fodje et al, 2012) with hardware advancements such as the standardization of sample holders and the development of robotic sample changers (Cipriani et al, 2006; Cohen et al, 2002; Jacquamet et al, 2009; Ohana et al, 2004; Pohl et al, 2004) that automate the transfer of cryocooled protein crystals to a goniometer prior to data collection
Until recently the small capacity of the sample-containing dewar associated with robotic sample changers and the need for manual interventions to recover from sample-changer errors has made this possibility unworkable
Summary
The automation of macromolecular crystallography (MX) experiments on synchrotron beamlines is aimed at increasing throughput and at simplifying data-collection and beamalignment protocols in what can be a complicated and stressful environment for novice users. The G-Rob suffered from several disadvantages, the most important being the dynamic correction required to reduce the sphere of confusion (SOC) during a complete rotation of the goniometer This prevented the use of pixel-array detectors in continuous readout mode and significantly reduces potential beamline throughput (Hulsen et al, 2006; Ferrer et al, 2013). A complete absence of diagnostics (such as detection of the presence or absence of a sample) made the autonomous operation of the G-Rob problematic Taking this knowledge into account, the ESRF launched a project to build a sample changer coupled to a built-in goniometer with the specifications required to be able to fully exploit high-brilliance undulator beamlines equipped with pixel-array detectors. Vertical and horizontal translations (X/Y) are performed using the table mounted below the robot
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