Dear Xplor mailing list,

I am trying to refine the NMR structure of three different stapled peptides 
(you may have seen my previous emails). For two out of three them, I have (with 
Charles's help) managed to produce structures that match the expected helical 
conformations, consistent with our CD data.


The third is proving more problematic, in that there are no obvious error 
messages being produced by Xplor, simply an "incorrect" structure. Our CD data 
shows that this stapled peptide is adopting a helix, as it was designed to do, 
but the structures coming out of Xplor have the stapled part disordered.


Interestingly, if I refine using the same .tbl files but use an unstapled 
model, I get a helical conformation (and a lot fewer violations!).


I attach results and input files for both stapled and unstapled runs. Does 
anyone have an suggestions as to why, without the helix-stabilising staple, the 
helix is returned? But if the staple is included, that part of the peptide it 
spans returns unstructured (and the violations rocket)?


Regards,

_________________________________________________________________
Dr. Douglas R. Houston
Senior Lecturer in Computational Biochemistry
Institute of Quantitative Biology, Biochemistry and Biotechnology
Room 3.23, Michael Swann Building
King's Buildings
University of Edinburgh
Edinburgh, EH9 3JR, UK
Tel. 0131 650 7358
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