[ccp4bb] crystallization optimization

[Liuqing Chen]

hello everyone!
I get a condition (10% w/v PEG 6000, 100mm HEPES PH7.0) in which my protein 
grow small  needle like crystals, how can i optimize it to get bigger crystals? 
 the attach is the crystals  figure.
thanks in advance
sincerely
Liuqing Chen