Enhanced Sample Handling for Analytical Ultracentrifugation with 3D-Printed Centerpieces.

The centerpiece of the sample cell assembly in analytical ultracentrifugation holds the sample solution between windows, sealed against high vacuum, and is shaped such that macromolecular migration in centrifugal fields exceeding 200 000g can proceed undisturbed by walls or convection while concentration profiles are imaged with optical detection systems aligned perpendicular to the plane of rotation. We have recently shown that 3D printing using various materials allows inexpensive and rapid manufacturing of centerpieces. In the present work, we expand this endeavor to examine the accuracy of the measured sedimentation process, as well as short-term durability of the centerpieces. We find that 3D-printed centerpieces can be used many times and can provide data equivalent in quality to commonly used commercial epoxy resin centerpieces. Furthermore, 3D printing enables novel designs adapted to particular experimental objectives because they offer unique opportunities, for example, to create well-defined curved surfaces, narrow channels, and embossed features. We present examples of centerpiece designs exploiting these capabilities for improved AUC experiments. This includes narrow sector centerpieces that substantially reduce the required sample volume while maintaining the standard optical path length; thin centerpieces with integrated window holders to provide very short optical pathlengths that reduce optical aberrations at high macromolecular concentrations; long-column centerpieces that increase the observable distance of macromolecular migration for higher-precision sedimentation coefficients; and three-sector centerpieces that allow doubling the number of samples in a single run while reducing the sample volumes. We find each of these designs allows unimpeded macromolecular sedimentation and can provide high-quality sedimentation data.

Using sound pulses to solve the crystal-harvesting bottleneck.

Crystal harvesting has proven to be difficult to automate and remains the rate-limiting step for many structure-determination and high-throughput screening projects. This has resulted in crystals being prepared more rapidly than they can be harvested for X-ray data collection. Fourth-generation synchrotrons will support extraordinarily rapid rates of data acquisition, putting further pressure on the crystal-harvesting bottleneck. Here, a simple solution is reported in which crystals can be acoustically harvested from slightly modified MiTeGen In Situ-1 crystallization plates. This technique uses an acoustic pulse to eject each crystal out of its crystallization well, through a short air column and onto a micro-mesh (improving on previous work, which required separately grown crystals to be transferred before harvesting). Crystals can be individually harvested or can be serially combined with a chemical library such as a fragment library.

Maintaining Microclimates during Nanoliter Chemical Dispensations Using Custom-Designed Source Plate Lids.

A method is described for using custom snap-on lids to protect chemicals in microtiter plates from evaporation and contamination. The lids contain apertures (diameter 1.5, 1.0, or 0.5 mm) through which the chemical building blocks can be transferred. The lid with 0.5 mm apertures was tested using a noncontact acoustic liquid handler; the 1.0 and 1.5 mm lids were tested using two tip-based liquid handlers. All of the lids reduced the rate at which solvents evaporated to room air, and greatly reduced the rate of contamination by water and oxygen from room air. In steady-state measurements, the lids reduced the rate of evaporation of methanol, 1-hexene, and water by 33% to 248%. In cycled experiments, the contamination of aqueous solvent with oxygen was reduced below detectability and the rate at which DMSO engorged atmospheric water was reduced by 81%. Our results demonstrate that the lids preserve the integrity of air-sensitive reagents during the time needed for different types of liquid handlers to perform dispensations. Controlling degradation and evaporation of chemical building blocks exposed to the atmosphere is increasingly useful as the reagent volume is reduced by advances in liquid handling technology, such as acoustic droplet ejection.