This is continuation of the previous message, which was sent prematurely. In case of crystals with one, very long unit cell data collection strategy needs to be carefully chosen.
Ad. 2) What would be a better way to collect data in the future? First, the detector needs to be placed far back enough, so that the spots are resolved; at minimum when the longest unit cell is in the plane of the detector (perpendicular to the beam). To satisfy this condition, it is best to rotate on the axis that is parallel (or close to parallel, within 30 degrees) to the longest unit cell. However, this can be difficult to achieve in some cases. There are two types of workaround in such a situation: a) if the crystal has low mosaicity, the spots may be resolved in angular direction, if a short oscillation is used to collect images; HKL has no problems with 0.1 degree oscillation range; b) in the case of mosaic crystals, when a) doesn't work, a partial solution is increase the detector distance. There will be still a region of reciprocal lattice where the data will be lost due to overlap, but this region may be small enough for the data to be used in structure solution. There is no indication that the particular crystal presented is twinned or highly mosaic, so chances are good that this project will be solved. Zbyszek Otwinowski > Hi CCP4 folks > I have a data set which is looks twinned ( see the image-1 - I zoomed on to the image so that one can spot the twinning. Furthermore, the spots are very smeary from ~ 30 - 120 degrees of data collection, see image 2) I tried using HKL2000 and mosflm to process this data but i cannot process it. I was wondering if anyone has any ideas as to how to process this data or comments on whether this data is even useful. Also, I would really appreciate if someone could share their experiences on solving twinning issues during crystal growth > Thanks in advance ! > Mahesh[image: Inline image 2][image: Inline image 3] Zbyszek Otwinowski UT Southwestern Medical Center at Dallas 5323 Harry Hines Blvd. Dallas, TX 75390-8816 Tel. 214-645-6385 Fax. 214-645-6353 Zbyszek Otwinowski UT Southwestern Medical Center at Dallas 5323 Harry Hines Blvd. Dallas, TX 75390-8816 Tel. 214-645-6385 Fax. 214-645-6353
