Dear Jobi,

For a crystal which is big in size(0.2-0.3mm is pretty big) while diffract poorly, dehydration (increase concentration of the precipitant slowly) is a good choice to improve diffraction, especially for those tends to crack during cryo.

Also those regular optimization approaches: Additive screen etc. Sometimes cleave the tag or change it to another end will work.

Cheers,

Bingfa

发件人: [log in to unmask] [mailto:[log in to unmask]] 代表 Jobichen Chacko
发送时间: 2011年4月13日 17:44
收件人: [log in to unmask]
主题: [ccp4bb] Crystal Optimization

Dear All,

We got crystals for a  35 KDa protein with 323aa including His tag and linker. It was originally  crystallized in 0.1M BisTris Propane pH:6.5, 0.2M Potassium thiocyanate and 20% PEG 3350. Later we managed to obtain crystals with 0.1M BisTris pH:6.5, 0.2M Potassium thiocyanate and 20% PEG 3350 as well.  Crystals are 3 dimensional in shape and 0.2-0.3mm long. Maximum resolution obtained till now is 5.8Å. Tried various cryo conditions like Oil, glycerol, salt and sugars. However, the resolution hasn't improved. The crystal tends to break in the presence of glycerol.

Kindly give your suggestions to improve the resolution.

Thanks.

Jobi