Abstract
Automated sample changers are now standard equipment for modern macromolecular crystallography synchrotron beamlines. Nevertheless, most are only compatible with a single type of sample holder and puck. Recent work aimed at reducing sample-handling efforts and crystal-alignment times at beamlines has resulted in a new generation of compact and precise sample holders for cryocrystallography: miniSPINE and NewPin [see the companion paper by Papp et al. (2017, Acta Cryst., D73, 829-840)]. With full data collection now possible within seconds at most advanced beamlines, and future fourth-generation synchrotron sources promising to extract data in a few tens of milliseconds, the time taken to mount and centre a sample is rate-limiting. In this context, a versatile and fast sample changer, FlexED8, has been developed that is compatible with the highly successful SPINE sample holder and with the miniSPINE and NewPin sample holders. Based on a six-axis industrial robot, FlexED8 is equipped with a tool changer and includes a novel open sample-storage dewar with a built-in ice-filtering system. With seven versatile puck slots, it can hold up to 112 SPINE sample holders in uni-pucks, or 252 miniSPINE or NewPin sample holders, with 36 samples per puck. Additionally, a double gripper, compatible with the SPINE sample holders and uni-pucks, allows a reduction in the sample-exchange time from 40 s, the typical time with a standard single gripper, to less than 5 s. Computer vision-based sample-transfer monitoring, sophisticated error handling and automatic error-recovery procedures ensure high reliability. The FlexED8 sample changer has been successfully tested under real conditions on a beamline.
Highlights
Some of the existing sample changers are equipped with tool changers that are able to switch between standard data collection and in situ data collection (Jacquamet et al, 2004), but most are only compatible with a single sample holder and puck model currently used in cryocrystallography
This paper focuses on the FlexED8 sample-changer model (Fig. 2), the first member of a family of sample-handling devices based on the Flex robotics that can be adapted to different dewars and experimental environments but retains the same core robotics and control software
The tip of the cryo-jet head was adjusted to a distance of 5 mm from the nominal position of the crystals and a 3 mm retraction was systematically applied during the gripper approach to avoid collision, this is only necessary when transferring SPINE/SPINEplus sample holders
Summary
Following the pioneering developments in automating sample transfer at macromolecular crystallography (MX) beamlines, and the standardization of sample holders used in cryocrystallography at the turn of the century (Cipriani et al, 2006; Cohen et al, 2002; Jacquamet et al, 2004, 2009; Ohana et al, 2004; Pohl et al, 2004), sample changers continue to develop to match the ever-increasing demand for storage capacity, transfer speed and fully automated data collection (Nurizzo et al, 2016; Russi et al, 2016; Ferrer et al, 2013). EEPROM chip using a 1-Wire communication protocol for gripper identification; (iv) a pneumatic jack to actuate the sample-holder locking mechanism of the gripper; (v) a heating resistor and a thermocouple to keep the base of the gripper at room temperature when its tip is parked in liquid nitrogen and (vi) a pneumatic port for deicing the inner part of the gripper tips with dry air or nitrogen gas The use of a tool changer in combination with gripper IDs, puck IDs and the puck-type detection system allows safe transfer between different sample holder models and minimizes the risk of collision owing to gripper and puck mismatch
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