Lin, consider yourself lucky if you only have one problem...;-) regarding your question, poor reproducibility is a common problem with membrane protein crystallography and is most likely caused by different amounts of lipids copurifying with your protein. If you want to avoid it (may not be possible altogether) do your preps as reproducible as possible, especially using the same amount of detergent per cell weight, stirring at the same speed, for the same time etc, etc. Even then it may be hard to control. I tend to use this "feature" as a screening variable and always do several preps to hopefully get one that works well and will allow you to solve a structure.
good luck, Bert ________________________________________ From: CCP4 bulletin board [CCP4BB@JISCMAIL.AC.UK] on behalf of Yibin Lin [yyb...@gmail.com] Sent: Monday, December 17, 2012 11:29 PM To: CCP4BB@JISCMAIL.AC.UK Subject: [ccp4bb] Phase separation and membrane protein crystallization Dear all, I am working with one membrane protein. I met one problem. From different purification protein (following same methods, never changing anything except "date and time"), I setup crystal plate using same conditions, why sometime I can get crystals and sometime only phase separation? Thanks, Lin
