[phenixbb] weak anomalous phasing (magic triangle I3C)

[ChenTiantian]

Dear all,

I'm working on a 18kD protein, the secondary structure prediction says most
of the structure is beta sheets, trying to solve the structure with SAD.
Heavy atom soaking gives several datasets with I, W, Au, range from
2.7~3.7A, however, the anomalous signal is pretty weak, I couldn't find a
reasonable solution.
We got a co-crystal dataset with the magic triangle I3C, extends to around
2.5A, this is the best data we got so far.
shelxc gives me the following result:

 Resl.   Inf. 12.59  7.75  5.84  4.77  4.08  3.59  3.22  2.94  2.70  2.51
2.35

 N(data)      79   257   429   635   811  1010  1235  1384  1698  1555  1954

 Chi-sq     0.69  0.63  0.60  0.67  0.61  0.88  1.05  1.02  0.80  0.55  0.42

 <I/sig>    79.4  34.1  30.3  32.2  31.8  26.6  21.1  14.6   8.3   3.9   2.4

 %Complete  94.0  98.1  97.5  99.5  99.4  99.0  99.7 100.0  99.9  85.4  96.1

 Multipl.    4.0   4.5   3.9   4.5   4.7   4.2   4.4   4.8   5.0   4.3   4.4

 R(pim)%    2.27  1.72  2.29  2.05  2.02  2.62  3.51  4.84  7.90 14.43 22.78

 Ranom%     6.49  3.68  5.19  4.29  4.27  6.35  9.50 12.97 20.90 33.58 52.21

 <d"/sig>   0.73  0.80  1.08  0.85  0.95  1.03  1.00  0.91  0.85  0.78  0.70

 CC(1/2)     5.1  41.7  68.8  38.1  42.7  49.9  49.9  25.5  24.9  13.3  -4.7



then I tried shelxd with different heavy atom sites number and resolution
cut, the best CC I got is CC/CCweak: 24.75/7.69,
and I can identify a triangle, (length: 6.5/6.5/5.0A), however, both shelxe
and autosol didn't end up with a promising result.

[image: image.png]
It would be great if anyone can give me some suggestions.

Thank you in advance!
-- 
Tiantian
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