Hi, Bernhard,

ok, sure, you are right ! Nevertheless, I would not be so desperate and categorical: you are right , at my knowledge also, there is currently NO known algorithm to take into account the "flat mask bulk solvent contribution" at the rotation step (maybe I am wrong?), however this does not mean it is impossible. The question is should it be done at all ?
     When do you the rotation search, you need to use mostly the highest resolution data, and it may be rather useful to remove the low-resolution data (see the tests described in Acta Cryst D51, 888-895, 1995; however, it looks like in practice nobody uses variable resolution for different MR steps). When you work at low resolution with envelopes, you do not care about bulk solvent correction since all this results indeed in a scale coefficient.
     There is a tiny (but not unusual) situation when one wants to do MR at the "worse" resolution of 9-12 A (worse in the sense that the maps show neither (already) molecular envelope nor (yet) clear structure. Suppose we could solve the MR problem - what we do then since the maps are so poor ? It is worthy in this case artificially lower the resolution ? I do not know...

However, I agree, you question is fully valid and is interesting.


All the best ,

Sacha

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De : [log in to unmask] [[log in to unmask]]
Envoyé : mercredi 4 février 2015 14:09
À : Alexandre OURJOUMTSEV; [log in to unmask]
Objet : RE: [ccp4bb] Bulk solvent correction in Phaser MR LF

Hi Sacha,

I was imprecise. With unplaced I meant ‘neither rotated nor translated’.

Once you become post-rotationally SF based, you can in fact compute a F(env)  

whole inclusion should improve the TF score.

What is not evident to me is how to use a mask and compute the Fs  if the orientation

(rotation) is yet to be determined?

Thx, BR