[phenixbb] anomalous signal to ~5.1 - 4.5Å

Randy John Read rjr27 at cam.ac.uk
Wed Dec 14 02:03:52 PST 2022

Dear Damon,

Is this a protein structure? If it is and you haven’t tried molecular replacement with AlphaFold models, that’s what I would do first. With such limited anomalous signal, you’re unlikely to be able to solve the substructure and, even if you could, the phases would be unlikely to be good enough to build anything. On the other hand, if you had a molecular replacement solution, you could use MR-SAD to find the substructure and supplement the MR phase information. By the way, the Phenix GUI for Phaser-MR (full-featured version) helpfully offers a button to open a task to run MR-SAD, where you typically only have to enter the anomalous scatterer type and maybe wavelength or f” information.

Best wishes,

Randy Read

> On 13 Dec 2022, at 22:12, Damon Wei <weizwann at gmail.com> wrote:
> You don't often get email from weizwann at gmail.com. Learn why this is important
> Dear colleagues,
> During the past few days, I have been trying to perform Experimental Phasing (SAD) using AutoSol. I am really curious to know if any of you have ever had any successful experience for phasing with anomalous signal only to ~5.1 - 4.5Å. In this scenario, will you use the default value (2.38 Å) in the “high-resolution limit” option in AutoSol, or a higher value like ~ 3-4 Å? How will you set the options including NCS copies, thoroughness, and resolution for running HySS?
> Any replies and help will be greatly appreciated!
> Best,
> Damon
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Randy J. Read
Department of Haematology, University of Cambridge
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