Dear CCP4bb community
I apologies for the slightly off topic post. We have recently had success crystallizing a membrane protein (diffraction > 3 Å at a synchrotron source) using the *in meso* method, the hit condition was from the Jena Bioscience screen Pi-minimal condition number #57. Hit condition – 47.1 % w/v PEG1000, 150 mM Tris pH 8.0, 80 mM Potassium bromide The screen is old and expired 12/20/2013 (lot # JBS00013133), we have tried to reproduce the crystals using homemade optimization screens around the hit condition but have not had any success. We have tried reproducing the hit using a new (not expired) Pi-minimal screen but had no success. We are only able to reproduce the crystals using the expired screen and we do not have much of it left. We went back and tested the pH of the condition that had given crystals, the expected pH was 7.9 but we found it to be 6 – 6.5 using a pH indicator strip. We believe the drop in pH is caused by oxidative degradation of the PEG1000 resulting in the formation of carboxylic acid species. We have contacted Jena Bioscience to try and get some of the old screen stock but unfortunately they do not have any. My question is does anyone out there happen to have any expired screen stocks of this Pi-minimal condition (#57), ideally from the same lot (lot # JB200013133), that they would be willing to send us. Does anyone have any advice as to how to reproduce the condition? We’ve considered bubbling oxygen through and heating the sample to accelerate the oxidation process. King Regards Jonathan Bailey (PhD student) Professor Martin Caffrey Lab MS&FB group Trinity College Dublin
