Dear Lisa,

the first thing to check is whether the polymerization is due to disulfide bond formation. If you run a gel of your protein with one sample boiled in the presence of b-mercapto ethanol and one sample boiled in the absence of bME, this should tell you whether disulfide links are the culprit. If disulfide links are the problem you could try adding DTT or TCEP to all your buffers, or to mutate the suspicious cysteines away.

Good luck!

Herman

Von: CCP4 bulletin board [mailto:[log in to unmask]] Im Auftrag von LISA
Gesendet: Montag, 17. Februar 2014 10:58
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Betreff: [ccp4bb] protein polymerization

Dear All,

My proein is polymerzated and elutate in the void volum when runnning gel filtration Superdex 200. I can get a small crystal after a  lot of optimization. But the resolution is still very low (about 8A ). I try to find the sites involved in polymerization. Is there some software to predicat the amino acids which are involved in protein polymerization? And All  suggestion to the crystal optimization are welcome.  Thank you.

Best Regards,

Lisa