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Industrial Liaison Group:
Tel: +44 (0) 1235 778797
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BioSAXS (or protein SAXS) has become an indispensable tool in biomedical science. Not only can researchers tell the mass and size of a biomolecule in solution, but they can reconstruct its basic shape, tell if it is rigid or flexible, and even figure out how multiple molecules fit together to form complex molecular machines. Increasingly, advances in medical research depend upon gaining a clear understanding of how biomolecules function and interact within the living cell.
BioSAXS is one of the few techniques that can yield structural information on how biomolecules behave under conditions very similar to the living cell. With the data collected during their BioSAXS experiments, researchers are able to gather a wealth of complex structural information about their sample including: determining physiological oligomeric states, validating proposed models of complexes, building complexes from monomers or known fragments, studying protein-protein interaction under different solution conditions, modelling missing loops and domains, refining homology models, categorising discrete folded and unfolded states, and finding volume fractions in mixtures.
Here at Diamond, Beamline B21 is dedicated to solution state protein SAXS that can accommodate a wide variety of aqueous-based and some limited organic solvent-based samples. B21 is a bending magnet beamline which offers users a stable, smooth energy range in which to carry out their research and it is this high intensity of X-rays that allows structural investigations of macromolecule solutions under relevant conditions, for example at different temperatures.
B21 is equipped with a highly automated BIOSAXS robot for small volume liquid handling from a 96 well plate and the small beam sizes mean that only small volumes (35µL) are required for measurements. Up until now the time taken to collect a full data set on a sample was around 3 mins. Although much faster than laboratory sources, the limited flux produced on B21 has meant that throughput has been constrained. However, users are now able make use of a recent upgrade to the beamline which has resulted in measurement times for each sample being dramatically sped up. This significant upgrade is as a result of a new monochromator.
Previously, the B21 monochromator was a double crystal monochromator (DCM), the function of which is to select and transmit the desired photon energy from the white synchrotron radiation beam. The DCM uses two parallel crystals in (+, –) configuration to produce a monochromatic exit beam and the desired energy is selected by both rotating the crystals and varying the Bragg angle whilst keeping the crystals parallel to one another. The new monochromator is a multilayer model which has a much more extensive bandwidth compared with the previous monochromator.
The main advantage of this is that it delivers many times the flux of a silicon monochromator making more efficient use of the continuous synchrotron radiation spectrum, yet preserving the narrow collimation of the incident synchrotron beam. First users of the beamline are already benefiting from the increased throughput which will only improve further (up to 60 times faster data collection) following the August shutdown and the further scheduled improvements to the beamline set up.
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So what now for beamline B21? A beamline will always have some aspect or property that limits its performance or range of applications. An upgrade that addresses this limitation will increase the performance of the beam line but will inevitably also expose the next most limiting factor.
B21 currently has an automated liquid handling platform for changing samples and this takes around 90 seconds to wash, rinse and dry the sample cell and load the next sample. Whilst the beamline has been flux limited, the sample handling time has not seemed unreasonable relative to an exposure time of around 3 minutes for an average sample. However, following the upgrade the exposure time drops to around 10 seconds. Suddenly a 90 second handling time becomes unreasonably long. Therefore a new sample cell will be the next development for the beamline team to consider.
"Our next big development project will see a new rapid sample handling platform with washing/loading times of just a few seconds. The exciting aspect of all of these upgrades is creating opportunities for science applications that are genuinely new. On B21 we are working towards developing high throughput screening of drug libraries using SAXS to measure conformational changes." Nathan Cowieson, B21 Beamline Scientist
We’re always happy to discuss any enquiries or talk about ways in which access to Diamond’s facilities may be beneficial to your business so please do give us a call on 01235 778797 or send us an e-mail. You can keep in touch with the latest development by following us on Twitter @DiamondILO or LinkedIn
Diamond Light Source is the UK's national synchrotron science facility, located at the Harwell Science and Innovation Campus in Oxfordshire.
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