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> > I am not sure how you would fare with SAD data directly.. > > If you would like a comparison, check out the refmac paper. http://journals.iucr.org/d/issues/2011/04/00/ba5152/index.html See Figure 1 - this shows model building with ARP/wARP on over 100 data sets using the different Refmac functions that you asked about. The "MLHL" function is using "phase and fom" or "Hendrickson-Lattman" coefficients The "Rice" function is "no prior phase information" and the "SAD" function is using "SAD data directly". The figure shows fraction of the model built automatically. If you see lot of red squares on the top left of the diagonal (which you do), this just means the SAD function outperforms the 'Rice' function and you see more Red squares then Blue circles, so SAD performs better than MLHL. You can get more information on individual functions from references cited in the Refmac paper. The top right shows data sets between 80-100% built by all functions: thus, if your model/map is good enough, any function can build it. For SAD data sets that we have collected here, we always use the SAD function even at the end of the refinement and found (unsurprisingly) a lower difference between R-free and R then other functions. As Garib mentioned, Pavol Skubak and/or I are happy to answer any questions. Best wishes, Raj > But beware - do the HLs etc combine phases from the existing model and the > anomalous signal - if so they may be biased towards the existing model, and > make it harder to correct > Eleanor > > On 5 Nov 2012, at 09:46, Qixu Cai wrote: > > > Dear all, > > > > What's the difference between "no prior phase information", "phase and > FOM", Hendrickson-Lattman coefficients", and "SAD data directly" in the > refmac5 GUI of CCP4i? > > > > I have a SAD dataset and solve the phase by phenix.autosol. Now I want > to refine the structure by refmac5, which kind of input above I should > choose? > > > > Another question is in the "Refinement Parameters" of refmac5. What's > the meaning of "Use experimental sigmas to weight Xray terms"? If I use > molecular replacement to solve the structure, shall I "uncheck" this item? > > > > Thanks very much for your help. > > > > Best wishes, > > > > Q. Cai > > >