Sample manipulation and data assembly for robust microcrystal synchrotron crystallography

Abstract

Micro-sized polyimide well-mounts for the manipulation of microcrystals and a data-assembly method for rotation data sets from many microcrystals are described.

Crystallography on a chip – without the chip: sheet-on-sheet sandwich

“…Indeed, polyimide (commercialized as Kapton) supports are available commercially (MiTeGen) in various forms and shapes and are used as micromounts. Recently, the well established micromesh mount was extended to a micro-sized well mount (Guo et al, 2018). Its small size (diameter 250 mm) is advantageous for cryocooling and rotation data collection at synchrotron sources but is a disadvantage for room-temperature SFX data collection at XFELs.…”

“…'Crystallography on a chip' has attracted significant attention in recent years (Zarrine-Afsar et al, 2012;Hunter et al, 2014;Cohen et al, 2014;Mueller et al, 2015;Murray et al, 2015;Roedig et al, 2015Roedig et al, , 2016Oghbaey et al, 2016;Baxter et al, 2016;Owen et al, 2017;Guo et al, 2018). 'Chip' in this context refers to a micro-patterned support consisting of a film (for example Kapton) or a wafer (for example silicon) fabricated using semiconductor-processing techniques.…”

“…In the case of through-holes, mild suction can be applied to the back of the chip as the crystal solution is spread on the front to pull the crystals gently into the holes (Oghbaey et al, 2016). Trapping can be improved by tapering through-holes to form funnels from front to back (Mueller et al, 2015) or by adding small through-holes in the well (Guo et al, 2018). In lieu of suction, filter paper can be lightly pressed against the back of the chip to wick away the solvent (Guo et al, 2018).…”

“…Trapping can be improved by tapering through-holes to form funnels from front to back (Mueller et al, 2015) or by adding small through-holes in the well (Guo et al, 2018). In lieu of suction, filter paper can be lightly pressed against the back of the chip to wick away the solvent (Guo et al, 2018). Throughholes must obviously be matched in size to the crystals or the crystals will be pulled through the holes and lost.…”

Making a difference in multi-data-set crystallography: simple and deterministic data-scaling/selection methods

“…The anomalous correlation between a single data set and a reference data set of all merged data sets, the relative anomalous correlation coefficient (RACC), was employed by Liu et al (2012) and was further combined with cluster analysis dependent on both unit-cell parameters and intensity correlations. Yet another selection procedure combines frame rejection based on relative correlation coefficients (RCC) and CC 1/2 , crystal rejection based on SmR merge (smoothed-frame R merge , as reported in AIMLESS; Evans & Murshudov, 2013) and further subset selection based on anomalous correlation coefficients (ACCs; Guo et al, 2018Guo et al, , 2019. As the existence of a Bijvoet partner in the data set is required for the calculation of an anomalous difference of a reflection, few (if any) reflections per data set are included in the calculation if the data sets are partial.…”