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Hi Charles,

Actually I also tried the method of Q. Liu et al and got one structure solved after merging 3 different datasets. The only thing different in my case is the Se-SAD phasing instead of Br. But the signal was also weak due to the disorder of incorporated Se in the protein crystals (I supposed so, because I used only 50% of Se-Met during the culture). So in my case, first I processed the data by XDS and made some resolution limitation according to the I/sigma and CCanom. I also did some limitation on the number of images because SCALA can only process not more than 10.000 images (remove the bad images according to the I/sigma and B-factor). And in fact, I did some combination between cut datasets and non-cut datasets and found that the cut datasets really gave me better merged datasets as some noises were removed and the resolution was limited, of course you also lose some information. But in our case, improving the weak anomalous signal to just enough for solving something is more important than losing some information of noise, so we need to be compromised. And any way, for facing with the weak anomalous signal issue, we usually collected such a high abundance of datasets, so losing some information of data is not the problem.

Hope you will be able to solve it.
Regards,
Thanh Nguyen





On Mon, Mar 2, 2015 at 5:19 AM, Andreas Förster <[log in to unmask]> wrote:
Hi Charles,

I don't know what multiscale does.  Probably the right thing.  If the anomalous signal is weaker after scaling of multiple datasets, non-isomorphism might be at fault.  Try Blend to scale your datasets. Blend is part of ccp4 and gives good graphical diagnostic feedback.


Andreas




On 01/03/2015 4:20, CPMAS Chen wrote:
Dear CCP4 users,

Recently, I got some datasets with weak anomalous Br signal. I tried to
merge them according to  Q. Liu et al Science 336, p1033 (2012). I am
using the script [log in to unmask] The merged dataset has WEAKER
anomalous signals.

Liu et al used SCALA for scaling and merging while multiscale@SSRL using
AIMLESS. Should this cause such a difference? The SCALA@SSRL has a
limitation on the number of frames it can process. So I cannot directly
check if this caused the difference.

Any suggestions?

Thanks!

Charles

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Charles Chen

Research Associate

University of Pittsburgh School of Medicine

Department of Anesthesiology

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Nguyen Hong Thanh, Ph.D. student
Lab 20B. Macromolecular Structures Department
Centro Nacional de Biotecnologia, CSIC
C/ Darwin 3, Campus de Cantoblanco
28049, Madrid, Spain
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Genetic Engineering Laboratory
Institute of BioTechnology
Viet Nam Academy of Science and Technology
18 Hoang Quoc Viet, Cau Giay, Hanoi, Vietnam