The study of proteins using X-ray diffraction either with synchrotrons or X-ray Free Electron Lasers (XFELS) has become ubiquitous. Of growing interest within the protein crystallographer community is the study of proteins as they interact with their environment. Such bodies of work are known as time resolved studies. These studies were not possible prior to the development of XFELS. These new machines have an order or magnitude higher beam power and the frequency with which it can be delivered in a comparable time scale of many of nature’s protein interactions. For many beamlines in the synchrotron community the sample is required to be cryogenically frozen to promote longevity of the sample in the beam prior to its destruction. With an XFEL such measurements can be carried out at room temperature and hence samples can be stimulated in timescales matching nature and data sets taken in both states, at rest and after turnover. Data collected at room temperature is also going to yield results more representative of the protein in its natural state. Current methods for sample delivery for such experiments are being carried out with samples being jetted through a partial vacuum environment with data collected through a Kapton window or using devices such as the tape drive that takes measurements in a helium environment with the sample delivered on a Kapton belt. Both suffer with attenuation or shadowing from the Kapton decreasing the fidelity of the data collected. For many samples of greatest interest, low volumes on the orders of microliters may require extensive production effort and represent the largest volumes available. These delivery methods for such samples are clearly not practical. An ideal delivery and containment system will present no additional material to the X-ray beamline, will allow for delivery of nanolitres or less of sample and should allow for manipulation, mixing or both of the sample in situ. Acoustic entrapment has been explored for a variety of X-ray applications as they have the potential to deliver on all of the ideal system characteristics described. For example work has been completed in which acoustics were used to position and support lysozyme crystals within an x-ray beam at a synchrotron facility. A number of beamline experiments, particularly those utilising low sample volumes, take place in a helium atmosphere, to minimise unintended environmental interactions, to minimise x-ray beam attenuation and to limit the evaporation rate. To date however, acoustic levitation for X-ray beam presentation has only been used in ambient air. In this work, we present an acoustic levitation system, assembled using commercial transducers, for sample confinement within ambient helium gas for initial testing with the VMXi and I24 at Diamond Light Source Ltd. The newly developed system will allow for the collection of x-ray diffraction data without any additional material for sample presentation and which utilises the smallest possible volume, reducing waste and opening up new application areas. 1.Nature 470.7332 (2011): 73-77. 2.Nature methods 14.4 (2017): 443-449. 3.Scientific reports 6 (2016): 25558 4.Nature 205.4968 (1965): 278-278.
Journal: TechConnect Briefs
Volume: 1, Advanced Materials: TechConnect Briefs 2018
Published: May 13, 2018
Pages: 36 - 39
Industry sector: Advanced Materials & Manufacturing
Topic: Materials Characterization & Imaging