Abstract
The installation of multi-axis goniometers such as the ESRF/EMBL miniKappa goniometer system has allowed the increased use of sample reorientation in macromolecular crystallography. Old and newly appearing data collection methods require precision and accuracy in crystal reorientation. The proper use of such multi-axis systems has necessitated the development of rapid and easy to perform methods for establishing and evaluating device calibration. A new diffraction-based method meeting these criteria has been developed for the calibration of the motors responsible for rotational motion. This method takes advantage of crystal symmetry by comparing the orientations of a sample rotated about a given axis and checking that the magnitude of the real rotation fits the calculated angle between these two orientations. Hence, the accuracy and precision of rotational motion can be assessed. This rotation calibration procedure has been performed on several beamlines at the ESRF and other synchrotrons. Some resulting data are presented here for reference.
Highlights
50 years after the kappa patent granted to Nonius (Poot, 1968), we can state that, multi-axis goniometers have long been exploited in the realm of smallmolecule crystallography, their size as well as implementation challenges at user-oriented facilities has limited their adoption by the macromolecular crystallography (MX) community
A major problem in MX continues to be radiation damage (Hendrickson, 1991; Zeldin et al, 2013), and it has been a major driving factor behind a great deal of innovation owing to its role in undermining MAD or SAD phasing experiments (Ravelli et al, 2005)
In the case of room-temperature data collection, where the amount of collectable isomorphous data from a single crystal is strongly limited by radiation damage, such a frequent and rapid acceleration can cause the sample to move relative to the original
Summary
50 years after the kappa patent granted to Nonius (Poot, 1968), we can state that, multi-axis goniometers have long been exploited in the realm of smallmolecule crystallography, their size as well as implementation challenges at user-oriented facilities has limited their adoption by the macromolecular crystallography (MX) community. A major problem in MX continues to be radiation damage (Hendrickson, 1991; Zeldin et al, 2013), and it has been a major driving factor behind a great deal of innovation owing to its role in undermining MAD (multi-wavelength anomalous dispersion) or SAD (single-wavelegth anomalous dispersion) phasing experiments (Ravelli et al, 2005). In the case of room-temperature data collection, where the amount of collectable isomorphous data from a single crystal is strongly limited by radiation damage, such a frequent and rapid acceleration can cause the sample to move relative to the original. In all such cases, the resulting data will be more susceptible to errors related to crystal misalignment or poor spindle synchronization
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