[ccp4bb]: Phasing with FeS cluster

[Paul Hubbard <phubbard@post.its.mcw.edu>]

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Hi all,

I am having trouble doing initial phasing for a protein with an FeS
cluster. MAD data at the Fe abs. edge is to 3A, and in-house native
anomalous is to 2.65A.

Due to the low resolution, I have been treating the 4Fe-4S cluster as a
single Uranium atom. Therefore I use f' and f'' values for U taken from
the Sasaki table. I fix these parameters for the in-house anomalous and
remote wavelength data sets, and allow both f' and f'' to be refined for
the inflection and peak wavelengths.

The problem is that the "y" coordinate moves by ~2A, and I get stupid
final values for f' and f'' for the inflection and peak wavelengths
(i.e., f' at inf. is 35.1671 and f'' is 10.405)

Any thoughts would be very much appreciated.

P.S: I have read the fancy-looking manual, and asked a number of people.
No luck there.

AGS.