Dear colleagues, we have collected 200 degrees worth of oscillation data on a selenomethionine derivative (1 "non-terminal" methionyl per 120 residues) to 2A resolution. XDS provides the following output: <COLLECT.LP> LATTICE- BRAVAIS- QUALITY UNIT CELL CONSTANTS (ANGSTROEM & DEGREES) CHARACTER LATTICE OF FIT a b c alpha beta gamma
* 44 aP 0.0 47.9 47.9 171.2 90.1 90.0 119.9 * 31 aP 0.4 47.9 47.9 171.2 89.9 90.0 60.1 * 39 mC 0.8 83.0 47.9 171.2 90.0 90.1 89.9 * 14 mC 2.2 47.9 82.9 171.2 90.0 90.1 90.0 * 34 mP 2.3 47.9 171.2 47.9 90.1 119.9 90.0 * 29 mC 2.6 47.9 82.9 171.2 90.0 90.1 90.0 * 38 oC 2.8 47.9 83.0 171.2 89.9 90.0 90.1 * 10 mC 2.8 83.0 47.9 171.2 90.0 90.1 89.9 * 13 oC 2.9 47.9 82.9 171.2 90.0 90.1 90.0 * 12 hP 3.4 47.9 47.9 171.2 90.1 90.0 119.9 35 mP 249.9 47.9 47.9 171.2 90.0 90.1 119.9 33 mP 250.4 47.9 47.9 171.2 90.0 90.1 119.9 32 oP 251.8 47.9 47.9 171.2 90.1 90.0 119.9 . . . SPACE-GROUP UNIT CELL CONSTANTS UNIQUE Rmeas COMPARED LATTICE- NUMBER a b c alpha beta gamma CHARACTER 5 82.9 48.0 171.3 90.0 90.0 90.0 13033 15.3 36401 10 mC 143 47.9 47.9 171.3 90.0 90.0 120.0 8371 17.4 41063 12 hP 149 47.9 47.9 171.3 90.0 90.0 120.0 4496 17.0 44938 12 hP 150 47.9 47.9 171.3 90.0 90.0 120.0 4720 16.8 44714 12 hP 168 47.9 47.9 171.3 90.0 90.0 120.0 4255 16.9 45179 12 hP * 177 47.9 47.9 171.3 90.0 90.0 120.0 2549 16.7 46885 12 hP 21 48.0 82.9 171.3 90.0 90.0 90.0 6758 15.1 42676 13 oC 5 48.0 82.9 171.3 90.0 90.1 90.0 12751 15.8 36683 14 mC 5 48.0 82.9 171.3 90.0 90.1 90.0 12751 15.8 36683 29 mC 1 47.9 47.9 171.3 89.9 90.0 60.1 24755 9.4 24679 31 aP 21 47.9 83.0 171.3 90.0 90.0 90.0 6765 9.2 42669 38 oC 3 47.9 171.3 47.9 90.0 119.9 90.0 12671 9.6 36763 34 mP 5 83.0 47.9 171.3 90.0 90.1 90.0 13029 8.9 36405 39 mC 1 47.9 47.9 171.3 90.1 90.0 119.9 24755 9.4 24679 44 aP </COLLECT.LP> We scaled reflections, with reasonable residuals, assuming space group P622 and have a reasonable solution in P6122. Refinement does not take us past an Rfree of aprrox. 0.4. The apparent quality of the model-phased map varies across the asymmetric unit. The L-test does not indicate merohedral twinning. Translational pseudosymmetry was not detected. <Merohedral> twinning has been tentatively ruled out. Before considering Order-Disorder-type crystal defects (as reviewed by Andrey Lebedev here: http://www.ysbl.york.ac.uk/mxstat/andrey/ecm2010.pdf), we would like to rule out that we might have erroneously applied too many symmetry constraints. To that end, we have scaled data in C2. We observed anomalous difference fourier peaks corresponding to positions of 6 selenium atoms in the current model, but refinement still does not proceed, and maps look similar to P6122 treatment. To "cover all bases" we would like to extend the asymmetric unit to P1. And here is the question: Does it suffice to pursue any one of the P1-associated lattices in the XDS table or do both need to be tested? Many thanks as always, Wolfram Tempel