On Feb 29, 2008, at 10:29, Johan Turkenburg wrote:
Hi,
You need to firstly check that you did the map calculation
correctly, see comments below:
Sun Tang wrote:
Dear All,
In my structures, I want to assign Mn or Ca ions for some
densities. But when I did not have anomalous density in CCP4i. I
am not sure whether I was correct. The following was what I did:
I processed the data with HKL2000 and select anomalous signal in
scaling. In CCP4i, I selected "Run FFT-Creat Map" in the "Map&
Mask Utilities".
What labels did you assign, and did you select 'anomalous map'?
This is crucial, as the protein (model) phase needs to be shifted
by 90 degrees, and this is done 'automatically' by FFT when you ask
for an anomalous map. Certainly with data of sufficient quality
collected on a home source with Cu radiation anomalous maps may
well show up such ions.
Exactly! Thats the most important bit to get right.
Another comment is that if you want to be sure about the nature of
the ions, you might want to try PIXE.
http://www.ee.surrey.ac.uk/IBC/index.php?target=13:68
I think all other suggestions are of course valid, but, without being
sure, the X-ray suggestions I see, need high resolution data ? PIXE
is a more direct method if it works well for your sample.
A.
I select "O format to cover asymmetric unit" and "Plot
section on Z axis from 0 to 1 in steps on 10". All others were by
default values. I display in ono10.
I collected the data at the wavelength of 1 A. Do I need to
adjust the wavelength to maximize the anomalous signal from Mn or Ca?
Any ideas and suggestions are greatly appreciated!
Sun Tang
---------------------------------------------------------------------
---
Never miss a thing. Make Yahoo your homepage. <http://
us.rd.yahoo.com/evt=51438/*http://www.yahoo.com/r/hs>
--
+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Dr. Johan P. Turkenburg X-ray facilities manager
York Structural Biology Laboratory
University of York Phone (+) 44 1904 328251
York YO10 5DD UK Fax (+) 44 1904 328266
+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
