NSRRC Activity Report 2022

Facility Development and Status 101 The average size of crystalline samples for structure determination has decreased markedly over recent years. Some challenging projects may only lead to tiny crystals or, in some cases, microcrystals. Poor-quality bulk crystals may also benefit from small portions of the sample being exposed to a small beam in search of better-quality data. To respond to the demand from the user community, a micro-focus protein beamline was proposed in 2018. The commissioning was finished in 2021, and it was opened to users at the end of the same year. The measured flux densities and beam sizes are shown in Table 1 and Fig. 1 . Selected beam size (µm) Measured beam size (µm, H × V) Defined flux (phs/s) Flux density (phs/s/µm 2 ) Time to Henderson limit (s) 1 2.9 × 1.8 8.6 × 10 11 1.6 × 10 11 0.24 5 4.8 × 2.6 1.7 × 10 12 1.4 × 10 11 0.29 10 11.0 × 8.0 3.4 × 10 12 3.9 × 10 10 1.03 20 20.0 × 20.0 6.5 × 10 12 1.6 × 10 10 2.45 30 29.0 × 30.0 8.7 × 10 12 1.0 × 10 10 3.99 40 36.0 × 42.0 8.7 × 10 12 5.7 × 10 10 6.99 50 46.0 × 50.0 8.6 × 10 12 3.7 × 10 9 10.69 60 55.0 × 62.0 8.6 × 10 12 2.5 × 10 9 15.96 70 67.0 × 67.0 8.5 × 10 12 1.7 × 10 9 23.08 80 77.0 × 73.0 8.4 × 10 12 1.3 × 10 9 30.46 90 86.0 × 83.0 8.3 × 10 12 1.0 × 10 8 38.58 100 92.0 × 96.0 8.3 × 10 12 9.4 × 10 8 42.59 The measured stabilities of energy and beam position are shown in Fig. 2 (see next page). The data shows that the beamline is sufficiently stable during the exposure and the flux density is sufficiently high for crystals of different sizes. Unfortunately, high flux density does not guarantee good-quality data. Microcrystals deteriorate quickly, and complete data usually cannot be collected from a single crystal. To address this issue, we have implemented a multi-crystal small-wedge strategy, 1 and several structures have been determined using this method. Automatic data collection and a data processing pipeline will also be integrated into our system in the future to increase beamline efficiency and the success rate of user experiments. Fig. 1 : (a) Measured beam size versus offset. (b) Measured flux densities versus beam size. Micro-Focus Protein Beamline at the TPS Table 1 : Measured flux densities and beam sizes.