Using sound pulses to solve the crystal-harvesting bottleneck.

Yasmin N Samara,Ludmila Leroy,Mary T Bollard,Denise Laspina,Haley M Brennan,Sean Mcsweeney,Alexei S Soares,Kazimierz Gofron,Stefanie L Campos,Jakub M Wlodek,Liam Mccarthy,Ramya Natarajan

doi:10.1107/s2059798318011506

Abstract

Crystal harvesting has proven to be difficult to automate and remains the rate-limiting step for many structure-determination and high-throughput screening projects. This has resulted in crystals being prepared more rapidly than they can be harvested for X-ray data collection. Fourth-generation synchrotrons will support extraordinarily rapid rates of data acquisition, putting further pressure on the crystal-harvesting bottleneck. Here, a simple solution is reported in which crystals can be acoustically harvested from slightly modified MiTeGen In Situ-1 crystallization plates. This technique uses an acoustic pulse to eject each crystal out of its crystallization well, through a short air column and onto a micro-mesh (improving on previous work, which required separately grown crystals to be transferred before harvesting). Crystals can be individually harvested or can be serially combined with a chemical library such as a fragment library.

Highlights

Acoustic droplet ejection (ADE) is an automated, keyboarddriven technology that can be used for growing protein crystals (Wu et al, 2016), improving the quality of protein crystals (Villasenor et al, 2010) and transferring protein crystals onto data-collection media (Soares et al, 2011) such as MiTeGen MicroMesh sample holders
We found that MiTeGen In Situ-1 crystallization plates are suitable for acoustic crystal harvesting with minimal modification that is readily achievable by lightly abrading the edge pedestal using sandpaper
Advances in automated protein production (Banci et al, 2006), automated crystallization (Bolanos-Garcia & Chayen, 2009) and end-station automation (Snell et al, 2004) have potentiated the goal of full automation, but crystal harvesting remains a stubborn bottleneck that prevents the output of crystallization facilities from matching the data-collection speeds available at next-generation synchrotrons (Berman et al, 2011)

Summary

Introduction

Acoustic droplet ejection (ADE) is an automated, keyboarddriven technology that can be used for growing protein crystals (Wu et al, 2016), improving the quality of protein crystals (Villasenor et al, 2010) and transferring protein crystals onto data-collection media (Soares et al, 2011) such as MiTeGen MicroMesh sample holders (hereafter referred to as ‘micromeshes’). ADE can be used to screen chemical libraries (Collins et al, 2017) using either cryocooled crystals (Yin et al, 2014) or room-temperature crystals (Teplitsky et al, 2015). All of these methods use momentum from a sound pulse to move liquids and/or suspended crystals from the source location through a short air column to the destination with high precision (Fig. 1). Acoustic crystal transfer using commercially available acoustic liquid handlers is gentle (no hand tools are required) and fast (2.33 Æ 0.04 harvests per second; Cuttitta et al, 2015).

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Conclusion