Alison, Given:

> There is a pseudo-translation with 55 % peak at a fractional 
> coordinate of 0.5, 0.5, 0.48.

I don't think you can be certain about:

> Systematic absences along a and b axis were observed thus the 
> dataset was scaled in P21212 space group.

Try testing all eight possible Ortho. sp. grps, and also be prepared to
consider P2 or P21.

The pseudo-centring you see in the self-Patterson would seem to be
consistent w/ I222 (or very unlikely, I212121), or perhaps (C222 or
C2221) with NCS?

>From Berhnard's Matthews Coeff. calc.
(http://www.ruppweb.org/Mattprob/):
 
+-----------------------------------------------------------------------
------+
 |  N(mol)      Prob(N)     Prob(N)        Vm         Vs         Mw
|
 |          for resolution  overall      A**3/Da   % solvent     Da
|
 
+-----------------------------------------------------------------------
------+
 |   1          0.0021      0.0027       10.77       88.58     9900.00
|
 |   2          0.0033      0.0053        5.38       77.15    19800.00
|
 |   3          0.0662      0.0920        3.59       65.73    29700.00
|
 |   4          0.4170      0.4550        2.69       54.31    39600.00
|
 |   5          0.4861      0.4267        2.15       42.88    49500.00
|
 |   6          0.0233      0.0156        1.79       31.46    59400.00
|
 |   7          0.0021      0.0027        1.54       20.04    69300.00
|
 
+-----------------------------------------------------------------------
------+
It looks like you have a higher symmetry (centered) space group, or you
have NCS.

Is your heavy atom search "space group agnostic"?

Dave

David Borhani, Ph.D.
D. E. Shaw Research, LLC
120 West Forty-Fifth Street, 39th Floor
New York, NY 10036
[email protected]
212-478-0698
http://www.deshawresearch.com

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