 |
 |
Hi Chenjun Tang, I have not followed the original discussion, so my apologies if I am repeating the device already given to you. Crystallization optimization is always a good idea - nothing beats good quality crystals. In addition, you should try collecting few images, especially in the "bad" orientation of the crystal, at ambient temperature, from the samples that have NOT been cryo-protected yet. You need to figure out if the cryo-protection and/or cryo-cooling are damaging your crystals. Best, Nukri Ruslan Sanishvili (Nukri), Ph.D. Macromolecular Crystallographer GM/CA@APS X-ray Science Division, ANL 9700 S. Cass Ave. Lemont, IL 60439 Tel: (630)252-0665 Fax: (630)252-0667 [log in to unmask] ________________________________ From: CCP4 bulletin board <[log in to unmask]> on behalf of Tang Chenjun <[log in to unmask]> Sent: Friday, July 28, 2017 2:21 AM To: [log in to unmask] Subject: Re: [ccp4bb] weird diffraction pattern Hi, Thanks to all who gave me suggestions concerning the weird diffraction pattern and I really appreciate it that Kay Diederichs help me processing my data set and answer my questions. Although the data set can be processed using HKL3000, XDS without problems, the Rwork/Rfree values are still above 0.5 after molecular replacement. There can be several reasons. 1) The structure change a lot after binding DNA, so it is not possible to find a solution using molecular replacement. 2) Strong radiation damage and 1.0 degree image widths prevent good integration results. It may be better to use 0.1 degree image widths. 3) Streaky spots appearing in certain directions because of anisotropy or lattice translocation disorder, or one very large unit cell dimension lying along the X-ray beam may also have an affect on data processing. Now I am optimizing the crystals to address these problems. Best wishes and thanks again for your help, Chenjun Tang