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On Wednesday 30 August 2006 11:15 am, William Scott wrote: > > Since there are regions of this molecule that (presumably) have > canonical A-form RNA helices, and these have Br-U in them at known > positions, I'd like to make use of the distance constraints these put > on the Br sites, as well as the Br absorption in the mad peak data. > > Is it possible to do molecular replacement using the Br anomalous > signal and model helices to help pin down the locations of the Br > atoms? This should be possible, although I can't think of a successful example to hold up. The general idea would be to dummy up a data set h k l (I+ - I-) And a MR probe that consisted of only the 11 Br atoms from an A-form helix. A likely stumbling block is that fact that some of your "intensities" would be negative. The programs will not like that, unless you can arrange to work only in Patterson space. -- Ethan A Merritt Biomolecular Structure Center University of Washington, Seattle WA
