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Hi Rob,

the answer to the question "how many molecules are in the ASU?" is only available after satisfactory model building and refinement. The Phaser results that you show indeed suggest 6 mols/ASU, but they don't prove it. If I were you, I'd give the 6-molecule solution the highest priority, and start to build and refine. But be prepared to revise your hypothesis if you find that some of the molecules overlap with others.

best,
Kay

On Wed, 13 Nov 2019 14:33:04 +0000, Robert S Phillips <[log in to unmask]> wrote:

>I have been working on a protein structure which has been hard to solve by molecular replacement.
>
>Unit cell: (60.6, 172.34, 196.42, 90, 90, 90)
>Space group: P 21 21 21
>
>The problem is that the homologues have only ~20% identity, and there are multiple chains in the asymmetric unit.  The question is how many.  It could be 4, 5, or 6 chains.
>
>N      solvent                           P
> 4      0.602           3.09            0.225
> 5      0.502           2.47            0.388
> 6      0.403           2.06            0.229
>
>I have run PHASER with 4, 5 and 6 chains.  I allowed it to search all possible space groups, and P212121 was the best solution.  These are the results.
>
>N          LLG           TFZ
>4          104.9        7.5
>5          137.5        7.7
>6          166.2        8.3
>
> Am I correct to conclude that there are 6 chains in the asymmetric unit?
>
>Rob
>
>Robert S. Phillips
>Professor of Chemistry and of Biochemistry and Molecular Biology
>University of Georgia
>Athens, GA 30602
>Phone: (706) 542-1996
>Fax: (706) 542-9454
>E-mail: [log in to unmask]
>Web:  http://tryptophan.net<https://pod51004.outlook.com/owa/redir.aspx?C=ccbf42ffea5f48b1bf8e9bb950454bab&URL=http%3a%2f%2ftryptophan.net>
>
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