Tim,
Not really. Fo's can be viewed as having 3 parts. 1) F from our modeled
structure, 2) F from what we can't model. This can be bulk solvent, partial
or multiple occupancies in low resolution structures, thermal anisotropy ,
etc. 3) F from random errors in measuring data. The first F is what we deal
with. The third F we can minimize by collecting high quality data. The
second F is usually crystal/space group dependent. It arises from
crystallization conditions, crystal morphology and intermolecular contacts.
Data from isomorphic crystals should have similar second F's so map (from
first F's) is cleaner.
Doug
-----Original Message-----
From: CCP4 bulletin board [mailto:[log in to unmask]] On Behalf Of Tim
Gruene
Sent: Wednesday, June 17, 2009 4:39 PM
To: [log in to unmask]
Subject: Re: [ccp4bb] Difference Map images
> I know that sometimes Fo(complex)-Fo(apo) cannot be done because of
> nonisomorphism. We've had a lot of success with this with the dioxygenases
> because there is no large scale alteration in the active site. As for the
> technique itself, Brian Matthews drilled this into me when I was a postdoc
> in his lab.
Wouldn't - in the case of non-isomorphsim - a molecular replacement with
the apo-form come closest to a Fo(complex)-Fo(apo) map?
Just a thought.
Tim
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