This subproject is one of many research subprojects utilizing theresources provided by a Center grant funded by NIH/NCRR. The subproject andinvestigator (PI) may have received primary funding from another NIH source,and thus could be represented in other CRISP entries. The institution listed isfor the Center, which is not necessarily the institution for the investigator.The development of instrumentation for an automated high throughput data collection system for solution x-ray scattering has been continued, combining a quartz capillary flow cell and a motorized sample changer under Blu-Ice control. We have developed an in-vacuum capillary cell, which eliminates two windows and minimizes background scattering level. This has benefitted a number of studies in which macromolecules of low molecular weight or at low concentrations are critical. A second cell, outside the vacuum flight path, has the advantage of ease of alignment and maintenance for the majority of solution scattering studies. Both flow cell are connected via thin Tygon tubing to a fluid Hamilton 540B dispenser, which is under Blu-Ice computer control, and a sample selector, which combines a refrigerated aluminum block accepting any of the standard micro-plates or several PCR tube strips (up to total 8x12 tubes), with three motorized miniature linear translation stages whose vertical arm holds a syringe needle for sample aliquot selection. A typical data collection sequence involves 1) selection of a sample aliquot on PCR tube strips, 2) transfer of the aliquot to the flow cell via a Tygon tube, 3) repetitive translation of sample aliquot within the quartz capillary at around 1 microliter per second, immediately followed by the initiation of a series of scattering data acquisition, 4) sample recovery to a PCR tube, 5) cleaning of the capillary and Tygon tubing. The automated sequence eliminates manual sample change, and has led to more efficient use of beam time. Future goals include improved reliability of sample loading, including the elimination of bubble formation.
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