Macromolecular crystallographers (MXers) have been mainly using single-axis goniometers, as these are simple, robust, user friendly and well accessible for automation. However, the call for more degrees of freedom to reorient the sample never faded. In fact, with the increase use of small anomalous signals collected on crystals close to an absorption edge, the old methods of collecting true redundant data are likely to become more and more important. More and more brilliant beamlines are damaging the crystals during the experiment and cause untreatable systematic errors that can only be optimally minimized by taking full advantage of the reorientation capabilities of recently developed multi-axis goniometers.
Kappa Workgroup has been established in 2004 by a few scientists with the aim of offering these advantages to the wide MX user community. The first meeting was hold at EMBL-Grenoble on 29th of September, 2004. Scientists from synchrotrons all around the world have joined the Workgroup and have formed a leading force in MX data collection methodology developments. The full potential of the collaboration has been achieved by attracting Instrument Control Engineers to guarantee the smooth integration of the new devices on the beamlines. As result, kappa goniometers are now offered on major facilities.
After 6 years, on the 20th and 21st of September 2010, EMBL-Grenoble hosted again the Meeting. Scientists and engineers coming together from 8 European Synchrotrons (Maxlab - Sweden, BESSY - Germany, Diamond - U.K., Soleil - France, SLS - Switzerland, ALBA - Spain , ESRF - France, PetraIII -Germany) and other research institutes (GlobalPhasing, EMBL) were joint remotely by colleagues at NE-CAT, APS from the U.S. The program included sessions with presentations and discussions on instrumentation (calibration, maintenance, goniometer integration with sample transfer systems), as well as on scientific applications (optimal orientations for different data collection scenarios, representation and consideration of instrument capabilities and restriction). The main goal of this meeting was to enhance the standard workflow of the MX experiments, and define a relationship between the crystallographic needs and the available extended experimental possibilities. In between the theoretical discussions, practical demonstration has been provided on the ESRF beamline, ID23-1 by the beamline scientist Alexander Popov. The figure on top shows the diffraction image captured during the workshop as the six-fold symmetry axis is aligned by the EMBL/ESRF MiniKappa Goniometer Head. This miniKappa goniometer head (see the figure on bottom) is available on all the beamlines of the ESRF MX group.