[buster-discuss] Occupancy refinement w/o residual repulsion

[Thomas Womack]

Dear Dr Cho,

BUSTER is unable to handle cases where there are two different residues for the same chain name and number, but has reasonably comprehensive handling of alternate conformations.

BUSTER will not allow atoms with conformation letter A to repel atoms with conformation letter B, though atoms with no conformation letter *will* repel atoms with a conformation letter.

What I would suggest: put your ADP as residue C1 with all the alternate-conformation codes being A, and your AMP+PO3 as residue C2 and C3 with all the alternate-conformation codes being B.

Then use something like
NOTE BUSTER_OCCSUM 1.00 0.02 C|1:N9.A C|2:N9.B

to force C1 and C2 to have occupancies summing to 1, and

NOTE BUSTER_SET c1 = { C|1 }
NOTE BUSTER_SET c2c3 = { C|2 - C|3 }
NOTE BUSTER_COMBINE OCC c1
NOTE BUSTER_COMBINE OCC c2c3

NOTE BUSTER_SET allrefocc = c1 + c2c3
NOTE BUSTER_SET allother = \ allrefocc
NOTE BUSTER_CONSTANT OCC allother

to force C1 to have a single occupancy, C2 and C3 to have the same occupancies, and the rest of the occupancies in the structure to be fixed.

If you have any more trouble please contact us again.

Yours sincerely,

Tom Womack (Global Phasing)