[ccp4bb]: REFMAC Vs CNS SigmaA maps

[Paul Hubbard <phubbard@post.its.mcw.edu>]

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Hello all,

I have been looking at improving the current map I have made from
MIR/MAD phases. Having traced 35% of the structure, I thought I'd give
SigmaA a try. I did the following:

REFMAC (5):
1) Rigid body refinement using 25 chains (secondary structure)
2) Restrained refinement
3) Calculated and viewed the SigmaA weighted maps

CNS:
1) Rigid body refinemnet using 25 chains (secondary structure)
2) Simulated annealing
3) Calculated and viewed the SigmaA weighted maps

My question is, why does REFMAC seems do have done such a good job of
the mFo-Fc map, whereas in CNS the map looks like junk? I've compared
the REFMAC mFo-Fc map with the original Fo map with MIR/MAD phases,
looking at regions I suspected were secondary structure but didn't model
in, and it suggests that there is little bias as these regions are
improved. Could I have fallen into a trap, and CNS is giving me the
right answer?

Thanks

AGS

--
Paul Hubbard
Dept. of Biochemistry
Medical College of Wisconsin
Phone: 414-456 4305
Fax: 414-456 6510
URL: iris9.biochem.mcw.edu