Accoustic Levitation of protein crystals

P. Docker, G. Leen, M. Ward, P. Aller, D. Axford
Diamond light source,
United Kingdom

Keywords: accoustic levitation, protein crystallography, X-ray diffraction, time resolved studies

Summary:

This work describes the development of the use of tractor beam levitation to present Protein crystals for X-ray diffraction experiments. To date crystals of lysozyme and inulin in their mother liquor have been presented to the beam and had their structures solved in 0.7 of a second. Early experiments looking for structural changes in lysozyme when ligands are added are also under way with promising early results. This latter experiment is what is termed time resolved as we are looking at nature as it changes in real time. By building dished arrays of sonic sounders you can create areas of high and low pressure and sample preferentially will sit at the sights of low pressure. The work to date is described in our recent publications including one in Nature Scientific Reports. Its the Author's intention to describe the body of work to investigate the proven methodology from more of a physics perspective. These dished arrays can indeed be placed in flat grids and using delays to them sounding to cause the areas of low pressure. This would facilitate moving sample around and carrying out mixing possibly prior to X-ray diffraction data being collected. By gaining a greater understanding of the physics of the system functions the levitating drops can be manipulated and smaller drops can be supported. Work with a UK company called Poly Pico who have developed an injection system that allows for drops as small as 10 picolitres to be ejected at up to 50KHz on demand will also be investigated to add reactants to already supported crystals. In deed if two of their ejection systems were used truly homogenous mixing can be carried out by building the mixed drop from two Pico systems until the unit required for x-ray interrogation is deposited in the levitating trap. Already this technology is demonstrating great promise and has facilitated data on two Synchrotron beam lines and soon will be tested at a neutron source as well as an XFEL.