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Something else to try would be the Protic Ionic Liquid kit from Hampton. I recently had crystals of a protein that would only grow as laminated stacks of plates. Optimizing the conditions and using an additive screen didn't improve crystal morphology. I tried the PIL kit from Hampton and was able to get single, thick plates in several conditions. At the ACA meeting in Hawaii a few years back, there was a poster about ageing your PEG solutions by microwaving them and letting them cool on the bench. This was the only way that the poster's author could get reproducible crystals of her target protein. Good Luck! Bryan From: CCP4 bulletin board [mailto:[log in to unmask]] On Behalf Of Regina Kettering Sent: Wednesday, August 24, 2011 2:47 PM To: [log in to unmask] Subject: Re: [ccp4bb] spherulites and PEG3350 Something to consider is the quality of the PEG 3350. We have found that different qualities of PEG 3350 can give different results, depending on the type and amount of contaminants. What used to be the Fluka PEG 3350 is now the pharm grade of PEG 3350 (aka Miralax). We use high quality PEG 3350 for normal screening, but switch to the highest quality grade we can get for optimizing. Regina ________________________________ From: Jan van Agthoven <[log in to unmask]> To: [log in to unmask] Sent: Wednesday, August 24, 2011 2:05 PM Subject: [ccp4bb] spherulites and PEG3350 Dear all, I recently obtained some spherulites while trying to crystallize my protein. The spherulites are manually reproducible, but changing pH, protein concentration, and salt concentration does not result in crystal formation. Microseeding with crushed spherulites isn't a solution either as it only yields new spherulites. Next stepp is the use of an optimization kit but I have a limited amount of material, and I start doubting that these are protein spherulites, as the spherulites are not particularly soft. The condition contains 15% PEG 3350 and 200 mM NaCl. Does anyone know if PEG 3350 forms easily spherulites around that concentration? Thanks, -------------------------------------------------------------------------- Confidentiality Notice: This message is private and may contain confidential and proprietary information. If you have received this message in error, please notify us and remove it from your system and note that you must not copy, distribute or take any action in reliance on it. Any unauthorized use or disclosure of the contents of this message is not permitted and may be unlawful.