BioCARS staff, in collaboration with Philip Anfinrud, Friedrich Schotte, and their colleagues from NIDDK/NIH, are completing infrastructure changes that aim to expand the time resolution of macromolecular diffraction experiments on the 14-ID beamline from 5ns to ~100 ps (see September 2007 news item for technical details). These enhancements are partly supported by funding from NIDDK/NIH.
The first 160ps time-resolved experiments on the newly upgraded 14-ID beamline were conducted in December 2007. The results are most promising. A single 160ps X-ray pulse in the APS hybrid mode was sufficient to generate a well-exposed Laue diffraction pattern of a hemoglobin crystal. The pattern was taken using a doubly focused X-ray beam (40 x 110 µm2 beam size at the sample) from two in-line undulators (U23 & U27), tuned to 12 keV.
With overlapping 35ps laser pulses and 160ps X-ray pulses focused on the sample, complete data sets were collected for several photosensitive crystals, at series of time delays between the laser and X-ray pulses. Resulting light-dark difference electron density maps are clearly interpretable and reveal successful partial reaction photo-initiation in the crystals. Data analysis is in progress.