I think Jacob is right. As long as protein crystals contain about 10% "dark matter"* not accounted for in any model, we cannot fake a "true" electron density map and it is then not surprising that an 2mFo-DFc map is closer to a model-based fake map than a map based on experimental phases.
HS
*This "dark matter" causes the best Rfactors for protein crystals to be ~15% instead of the 5% measurement errors and may include disorder, anisotropy, imperfectly modelled solvent etc.
-----Ursprüngliche Nachricht-----
Von: CCP4 bulletin board [mailto:[log in to unmask]] Im Auftrag von Keller, Jacob
Gesendet: Donnerstag, 6. Dezember 2018 04:37
An: [log in to unmask]
Betreff: [EXTERNAL] Re: [ccp4bb] Experimental phasing vs molecular replacement
>>That said, model phases are not so bad. In fact, in all my experiments with fake data the model-phased 2mFo-DFc map always has the best correlation to the "true" map. If you substitute the "true" phases and use the 2mFo-DFc coefficients you actually make things worse. Counter-intuitive, but true.
I don't understand what you mean by true and fake here--can you clarify? How are the true map and phases generated (from an original true model, I assume?), and how are the fake data generated? (Also from the true model?) I am wondering whether there is some circular reasoning?
JPK
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