Enhanced capabilities for multi-crystal data collection based on double mesh scans.

Two-dimensional X-ray mesh (raster) scans are broadly used in macromolecular crystallography to identify positions on the sample holder at which diffraction images can be collected. Based on a single mesh scan, the commonly known method Mesh&Collect allows the collection of small angular wedges of diffraction data from multiple crystals identified in the mesh-scan area. Recently, the capabilities of the method have been extended by using two mesh scans instead of one. The scans are usually performed at orthogonal orientations of the rotation axis, or any other angular difference less than 90° can be used. This allows the more accurate determination, when compared with a single mesh scan, of the 3D centre positions of each crystal contained in the scanned area and gives better estimates of their dimensions and diffraction qualities. We present the upgraded DoubleMesh&Collect method based on the Dozor, Dozor-m2 and Resheteau software programs which automatically analyse the diffraction images of the two mesh scans. The applicability of the method is demonstrated on several cases, including room-temperature diffraction studies. The problem of cartography of large crystals is discussed.