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Hi Linda and all, 

Thank you very much for your suggestion. 

I just help to solve the structure of this protein. And I'm not sure if the 
protein is properly sequenced first. I'll confirm the sequence first. I'll let 
you know if it is not the sequence's problem. 


I very appreciate help from all you guys, so quick and helpful. 

Best wishes, 

Vinson 




________________________________
发件人： Linda Schuldt <[log in to unmask]>
收件人： [log in to unmask]
发送日期： 2010/11/24 (周三) 9:35:33 下午
主 题： Re: [ccp4bb] Strange density on Serine oxygen.

Hi Vinson,

along these lines: did you check the molecular weight of your protein with
MS? This should help to answer if the molecular weight deviates from the
expected one.

Best wishes,
Linda

Savvas Savvides schrieb:
> 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>
>
>