[sharp-discuss] questions about phases from MAD results

[Clemens Vonrhein]

Dear Yi,

autoSHARP will use/combine this information in several places, e.g.:

  1. when detecting heavy-atoms (using SHELXC/SHELXD) it will first
     try 3-wavelength MAD, then peak-SAD and finally 2-wavelength MAD
     (with the first two wavelengths). The best solution found will be
     used.

     The idea is to have a fall-back plan if the normal 3-wvl MAD
     approach doesn't work (e.g. radiation damage sets in).

  2. when the actual refinement and phasing is done in SHARP, all
     wavelengths are used at the same time (basically 6 measurements:
     F+ and F- from each wavelength). For more details see

       La Fortelle, E. de & Bricogne, G. (1997) Methods in Enzymology,
       Macromolecular Crystallography, volume 276, pp.  472-494,
       edited by R. M. Sweet and C. W. Carter, Jr. New York: Academic
       Press.

     and

       G. Bricogne, C. Vonrhein, C. Flensburg, M. Schiltz &
       W. Paciorek (2003). Generation, representation and flow of
       phase information in structure determination: recent
       developments in and around SHARP 2.0. Acta D59, 2023-2030.

The good thing about autoSHARP is, that it should be quite verbose
about what it is actually doing. And there is quite a bit of
documentation (e.g. hyperlinked from the output HTML pages from an
autoSHARP run).

Hope that helps - or maybe you have more specific questions?

Cheers

Clemens


On Wed, Apr 04, 2007 at 12:52:11PM -0500, Yi Xue wrote:
> Dear all:
>    I have a general question about sharp/autosharp on MAD phasing.
>    For a 3-wavelength MAD data, there are a lot of information, e.g.
> anomalous info inside three wavelengths, dispersive differences between
> different wavelengths, how does sharp/autosharp pick and combine the rich
> information to detect, refine the heavy atoms sites, and to generate the
> initial phases?
>    All comments are welcome.
> 
> thanks
> Yi
> 
> 
> 
> 
> 
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> sharp-discuss mailing list
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