Dear Ariela, in case your resolution is better than 1.2A, you can use direct methods. They might work up to 1.5'ish A resolution. MR requires a structural similarity between the search model and the target. For a cyclic polypeptide, this might be tricky to predict. You can, of course, try MR with a single, rigid amino acid, either directly with Phaser, or as part of Arcimboldo. Best, Tim On Thu, 10 Mar 2022 04:15:34 +0000 Ariela Samantha wrote:

Dear all,

I have collected an XRD data from a crystal of cyclic polypeptide with non-standard amino acid (2,4-diaminobutyric acid). Is it possible to solve the structure by molecular replacement? Or does anyone have any suggestion for solving the structure? Thank you very much for your kind help.

--- Best regards,

Ariela Samantha PhD Candidate Department of Structural Biology School of Molecular Sciences The University of Western Australia Bayliss Building room 4.26 Phone +61 8 6488 ext. 3163

-- -- Tim Gruene Head of the Centre for X-ray Structure Analysis Faculty of Chemistry University of Vienna Phone: +43-1-4277-70202 GPG Key ID = A46BEE1A