P12 is a small angle scattering (SAXS) beamline run by the EMBL at the PETRA III storage ring (DESY, Hamburg). The beamline is dedicated to the studies of biological macromolecules in solution using a high-throughput sample delivery robot and also in-line size exclusion chromatography (SEC-SAXS) with multi-angle laser light scattering and dynamic scattering options (MALLS/DLS). Automatic data collection, reduction and analyses are performed in near-real time making it easy to collect and as interpret the SAXS data for hundreds of visiting scientists who access P12 as part of an extensive user program [1, 2, 3].
The high flux available at P12 (5*1012 photons/second with a double crystal monochromator or 4*1014 with a double multilayer monochromator) allow one to study time dependent protein reactions in a broad temporal range, from fractions of seconds to minutes or hours. Using this high beam flux, in combination with P12’s optimized low instrument background and noise-free PILATUS 6M detector, it is possible to access the sub-millisecond time regime and collect interpretable SAXS measurements from low quantities of protein solution in just 100 microseconds. A fast-rotating beam chopper has recently been installed at P12 to deliver X-ray pulses and allow for even shorter time scales and fine control over sample exposures that can be used with coordinated ‘pump-probe’ experiments, for example, using a Nd:YAG EKSPLA laser in the newly-installed P12-laser hutch.
Successful experiments have also been performed at P12 utilizing anomalous scattering to gain additional information on the distribution of specific heavy atoms in proteins. Recent results obtained at P12 using high-flux, time-resolved and anomalous scattering techniques are diversifying and advancing synchrotron SAXS into new areas of structural biology research.
[1] Blanchet et al. J.Appl.Cryst.48, 431-443. (2015).
[2] Franke D. et al. Nucl.Instruments Methods 689,52(2012)
[3] Hajizadeh N.R. et al. J. Synchrotron Radiat.25,906(2018)
