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See detailToward a Definition of X-ray Crystal Quality
Maes, Dominique; Evrard, Christine ULg; Gavira, Jose et al

in Crystal Growth & Design (2008), 8(12), 4284-4290

Crystal X-ray quality is usually evaluated by looking at data quality parameters such as (relative) Wilson B-factor, resolution, R-factors, signal-to-noise ratio, and others. As these parameters are ... [more ▼]

Crystal X-ray quality is usually evaluated by looking at data quality parameters such as (relative) Wilson B-factor, resolution, R-factors, signal-to-noise ratio, and others. As these parameters are correlated, most studies focus on one or two of them. As part of a study of the effects of microgravity on X-ray quality, full data sets of 35 ferritin crystals (17 PromISS-4 “space” crystals and 18 from the ground control) were collected. Sixty-three parameters commonly used as indicative of X-ray data quality taken from the output of the processing, scaling, and merging software packages were analyzed. This highly dimensional “quality parameter dataset” was reduced using a principal component analysis. About 78% of the variability in the data set could be explained with the first four principal components. A score-plot in this four-dimensional space clearly showed two tendencies, one for the crystals grown in space and one for the ground crystals. The differences between the two groups are observed irrespective of the software package. They can be attributed to the first principal component and reflect the superior quality of the space crystals. [less ▲]

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See detailCounterdiffusion protein crystallisation in microgravity and its observation with PromISS (Protein Microscope for the International Space Station)
Zegers, Ingrid; Carotenuto, Luigi; Evrard, Christine ULg et al

in Microgravity Science and Technology (2006), XVIII

The crystallisation by counterdiffusion is a very efficient technique for obtaining high-quality protein crystals. A prerequisite for the use of counterdiffusion techniques is that mass transport must be ... [more ▼]

The crystallisation by counterdiffusion is a very efficient technique for obtaining high-quality protein crystals. A prerequisite for the use of counterdiffusion techniques is that mass transport must be controlled by diffusion alone. Sedimentation and convection can be avoided by either working in gelled systems, working in systems of small dimensions, or in the absence of gravity. We present the results from experiments performed on the ISS using the Protein Microscope for the International Space Station (PromISS), using digital holography to visualise crystal growth processes. We extensively characterised three model proteins for these experiments (cablys3*lysozyme, triose phosphate isomerase, and parvalbumin) and used these to assess the ISS as an environment for crystallisation by counterdiffusion. The possibility to visualise growth and movement of crystals in different types of experiments (capillary counterdiffusion and batch-type) is important, as movement of crystals is clearly not negligible. [less ▲]

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