On Fri, Sep 3, 2010 at 8:23 AM, Lionel Costenaro wrote:

occupancies {       constrained_group {         selection = "(chain A or chain B) and (resseq 105 or resseq 110:112 or resseq 140:143) and altid A"

After refinement, all alt_A selected residues do have the same occupancy, but not the same occupancies for alt_B and the sum for one residue (occu alt_A +occu alt_B) is not 1. Adding a second group with the same selection but "altid B", constrains also the alt_B occupancies but the sum is still not 1.

Do you mean you added a second "constrained_group" block? This is incorrect - you should use multiple selections instead: occupancies { constrained_group { selection = "(chain A or chain B) and (resseq 105 or resseq 110:112 or resseq 140:143) and altid A" selection = "(chain A or chain B) and (resseq 105 or resseq 110:112 or resseq 140:143) and altid B" } } I think that will force the sum of occupancies to be 1. -Nat

Hi Lionel,

A portion of my structure have two conformations at an interface between two (NCS) protein chains -in addition to other alternates conformations elsewhere. In both chains, I defined alt_A as one conformation and alt_B as the second conformation, and also for the waters in this region. I would like to constrained the occupancy of these conformations. I though that the following selections would do the job:

occupancies { constrained_group { selection = "(chain A or chain B) and (resseq 105 or resseq 110:112 or resseq 140:143) and altid A"

yes, Nat is correct: you need to define two selections - one for altloc_A and the other one for altloc_B: occupancies { constrained_group { selection = "chain A and resseq 105 and altloc A" selection = "chain B and resseq 105 and altloc B" } } Essentially, the above selection tells: "alternative conformation A of residue 105 in chain A is coupled with alternative conformation B of (NCS related) residue 105 in chain B". The sum of refined occupancies will be 1 in this case. It is essential that altlocs in both selections are different - this turn the non-bonded interaction off so the residues will get pushed apart. If you still having problems with this then please send me your PDB file and explain what should be constrained to what, and I will send you the working solution. I'm not sure I understood your question about waters. Pavel.