Acoustic methods for high-throughput protein crystal mounting at next-generation macromolecular crystallographic beamlines

Abstract

To take full advantage of advanced data collection techniques and high beam flux at next-generation macromolecular crystallography beamlines, rapid and reliable methods will be needed to mount and align many samples per second. One approach is to use an acoustic ejector to eject crystal-containing droplets onto a solid X-ray transparent surface, which can then be positioned and rotated for data collection. Proof-of-concept experiments were conducted at the National Synchrotron Light Source on thermolysin crystals acoustically ejected onto a polyimide `conveyor belt'. Small wedges of data were collected on each crystal, and a complete dataset was assembled from a well diffracting subset of these crystals. Future developments and implementation will focus on achieving ejection and translation of single droplets at a rate of over one hundred per second.

Keywords: X-ray diffraction; acoustic droplet ejection; conveyor belt; crystal mounting; high throughput; macromolecular crystallography.

Figure 1

Computer design of an ADE ejector and conveyor belt. A motorized two-roller conveyor belt apparatus attaches to a goniometer via an attachment plate. A 16-well magnetic base-mounted sample holder and transducer sit below the conveyor belt. A coupling tube containing water couples the transducer to the underside of the sample holder.

Figure 2

ADE ejector and conveyor belt testing at X25 at NSLS. (a) Ejection position. The conveyor belt is positioned directly over the sample well, outside of the Cryostream gas stream, ready to receive a droplet on the underside of the Kapton belt. (b) Collect position. Following droplet ejection, the conveyor belt is translated up, rotated 90°, and the belt is translated so that the droplet is in the cold gas stream and beam path.