hello everyone, I would like to seek your opinion on my crystal hits. I am working on a helicase
of which the native structure is solved and the all solution statistics are fine. I am trying to crystallize and solve the structure of the protein/ssDNA complex. I recently got some hits from commercial screens using sitting drop vapor diffusion. After crystallization optimization, these crystals diffract weakly but to 3.2 Angstroms for the longer exposure time. However, when the crystals rotate between 120 degrees to 180 degrees, the spots become streaky (attached), no matter the crystals are hexagonal or flaky. I have tried to determine the structure by molecular replacement method, but the Rwork/Rfree values are huge (above 0.5) and can’t be reduced further. I suspect the obtained crystals quality and resulting processed statistics is the reason for the observed high Rwork/Rfree values. Are there any suggestions? All comments will be appreciated! Best, Chenjun Tang
