Protein crystal presentation for synchrotron methods:acoustic techniques

Abstract

This thesis describes the design, development and testing of novel acoustic mounting methods for the diffraction of protein crystals for structural biology. Sample environment and presentation is a challenging field set within the larger subject of protein crystallography. The needs of researchers to achieve the highest resolution data collection from difficult to fabricate samples, sits alongside the need for complex experimental conditions, where temperature, hydration and chemistry must be altered and controlled. A movement within the structural biology field away from obtaining structures at cryogenic temperatures, towards high resolution structures at room temperature, where proteins may still function, has been the driver to search for novel solutions. To approach this ‘solution space’ the following work draws on acoustic manipulation techniques, looking for self-assembly and non-contact manipulation. Thus for the first time acoustic standing wave crystal trapping and also acoustically induced rotation have been shown in situ to be viable for use with protein crystallography, a fundamental proof paving the way for new time resolved and high throughput methods. The methods investigated included both surface acoustic and bulk acoustic waves, looking at self-assembly and flow induced rotation. Each demonstration addresses a fundamental need within the automation of room temperature crystallography, demonstrating both the technique and quantifying the diffraction resolution for the first time. Through the completion of these novel experiments acoustic sample presentation has been proven viable. The demonstrated method does not require crystals be removed from crystallisation fluid before mounting (using the acoustic trapping method), thus enabling the application of secondary fluids and paving the way for a fully continuous and microfluidic technology. Moreover acoustic goniometry lends itself to the automated mounting and collection of small batch crystal data by removing the need for delicate spine mounting. Both methods constitute a significant extension in the ability of researchers to utilise non-contact methods to control and interact with their proteins and crystals at room temperature.