Dear Savas and all,
Thank you very much for all your quick suggestions. I have tried Tyr and it turns out to fit the density very well. I will have the protein sequenced again to see if it is wrong sequece or O-linked glycosylation. I'll let you know if it turns out to be O-linked glycosylation. All the best, Vinson ________________________________ 发件人： Savvas Savvides <savvas.savvi...@ugent.be> 收件人： Vinson LIANG <lwg_conrad_1...@yahoo.com.cn> 抄 送： CCP4BB@JISCMAIL.AC.UK 发送日期： 2010/11/24 (周三) 9:27:31 下午 主 题： Re: [ccp4bb] Strange density on Serine oxygen. Hi Vinson Beyond the possibility for another type of residue as already suggested by Phil and Mark, there is also the possibility of O-linked glycosylation of the serine and threonine, if your protein undergoes such post-translational modification and it has been expressed via an expression system that processes the protein in that way. Ser/Thr tandems are well known targets for O-glycosylation (http://www.cbs.dtu.dk/databases/OGLYCBASE/). best regards Savvas ---- Savvas Savvides Unit for Structural Biology @ L-ProBE Ghent University K.L. Ledeganckstraat 35, 9000 Ghent, Belgium Ph. +32 (0)472 928 519 http://www.LProBE.ugent.be/xray.html On 24 Nov 2010, at 13:10, Vinson LIANG wrote: Dear all, > >I'm refining a structure and find some strange triangle density on the oxygen >of >Ser and Thr at the C terminus. One picture of the strange density is attached >here. Could anyone please give me some suggestions on what this could be? > >The buffer used during purification is PBS, Tris and NaCl. And crystallization >condition contains PEG3,350 and Mg(NO3)2. > >Thank you all in advance for any suggestion. > >Best, > >Vinson Liang > > > <triangle_density.gif>
