Date Published: August 01, 2016
Publisher: International Union of Crystallography
Author(s): Didier Nurizzo, Matthew W. Bowler, Hugo Caserotto, Fabien Dobias, Thierry Giraud, John Surr, Nicolas Guichard, Gergely Papp, Matias Guijarro, Christoph Mueller-Dieckmann, David Flot, Sean McSweeney, Florent Cipriani, Pascal Theveneau, Gordon A. Leonard.
An industrial six-axis robot has been combined with a high-accuracy air-bearing rotation axis to create a single device with the capabilities of both transferring cryocooled protein crystals from a sample-containing dewar and collecting complete X-ray diffraction data sets.
The automation of macromolecular crystallography (MX) experiments on synchrotron beamlines is aimed at increasing throughput and at simplifying data-collection and beam-alignment 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; Delagenière 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. The automation protocols available at nearly all synchrotron-based MX beamlines now routinely allow the collection and analysis of diffraction data from several hundreds of crystals in a typical experimental session (Beteva et al., 2006 ▸; Bowler et al., 2010 ▸; Elsliger et al., 2010 ▸; Ferrer et al., 2013 ▸; Heinemann et al., 2003 ▸; Holton & Alber, 2004 ▸; Malbet-Monaco et al., 2013 ▸; Monaco et al., 2013 ▸; Nurizzo et al., 2006 ▸; Okazaki et al., 2008 ▸) and, in principle, allow their completely unattended operation. However, 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. The standard mode of operation of MX beamlines is thus that data collection is still carried out by users, either present at the beamline or remotely.
The RoboDiff consists of an HCD coupled to a six-axis robotic arm mounted with a stack comprising an air-bearing rotation axis, centring tables and an electromagnet. The device can be divided into two highly correlated entities: the sample changer that performs the transfer of samples from the HCD to the beam position, and the goniometer that performs the data collection. The main advantage of this approach is that many of the parts are used by both components. For example, the same electromagnet is used to maintain the sample pin in position during data collection and for picking the sample from the HCD. By reducing the complexity of the system and integrating all functions in a single device, error handling and troubleshooting are efficiently treated at a low level, with a net gain in reliability.
The RoboDiff has been designed for high reliability and stability. This has been achieved by integrating a number of diagnostic tools in the sample changer and goniometer. Considerable effort has been made both to transfer the experience of beamline scientists to the software and to implement the ability to recover from situations that could otherwise prevent the continuation of experiments. To date, over 20 000 user samples have been loaded, characterized and collected. The 240 samples which can be stored in the HCD increase the throughput and allow MASSIF-1 to run unattended 24 h a day. The hardware and software is all owned by ESRF, making maintenance and developments very flexible. Moreover, several collaborations based on the RoboDiff project have been set up to allow dispersion of the technology all over the world. The close links that have been designed between the RoboDiff and the ISPyB database and MXCuBE brings MASSIF-1 to the forefront of instruments for structural biology, and provide one of the missing steps in the automatic gene-to-protein pipeline.