Two of the major milestones in commissioning a beamline have been achieved on 24-ID-E at NE-CAT.  On August 9, 2024, x-rays were delivered by the APS through the Sector 24 front end. Using an ultrasensitive camera focused through a port of the monochromator, APS physicists detected the beam on the monochromator silicon crystals of both 24-ID-C and 24-ID-E. Though the focus was rough, NE-CAT was able to observe the beam.  After the September shutdown, Dr. Malcolm Capel was able to carefully steer the beam through the experimental hutches to the sample position over the next two months.

The upgraded APS now delivers an extremely small beam with almost no horizontal divergence.  As the light source has reduced in size, the flux density has increased.  However, this means that the beam is extremely sensitive to vibration from mechanical sources.  Excessive beam motion with a pinpoint source means that with small samples and fast data collection, the beam could move off the sample during data collection, resulting in a decrease in data quality.  Working with the APS, NE-CAT spent several weeks attempting to reduce beam motion.  Finally, on November 21, 2024, with the beam motion reduced to a negligible amount, we collected a complete, native thaumatin dataset to 1.3 Å in 14.4 seconds on 24-ID-E using 10 msec exposures.  Molecular Replacement produces a beautiful electron density map.

On November 23, 2024, after collecting 1440 degrees of data for over 50-fold redundancy, Dr. Igor Kourinov was able to perform sulfur-SAD phasing on thaumatin.  The electron density from the sulfur-SAD phasing clearly shows disulfide linkages in the structure. 24-ID-E is calibrated to above the Se edge with only 0.23 electrons available at this energy for anomalous phasing from sulfur.  In contrast, selenium has 3.84 electrons available at this energy.  This shows that the beam is stable enough for high-quality data collection.

Join us in celebrating these major milestones.  They indicate that we will be welcoming back users soon!