Frank,
When a symmetry interface is known, say in P2, then a distance restraint can be used in the Contacts file. In the case of IDP, you do not expect a symmetric dimer, so the Overall Symmetry should be set to [A]symmetry.
So how best to model your interface. Do you have (1) a core beta sheet interaction, which can be placed at the origin to fix the P2 symmetry, (2) a small dimerization domain, determined by homology, or (3) is its structure completely unknown, in which case just give a residue range in the Contacts file.
If residues (1-5) interact with the symmetry residues (15-20), antiparallel interface, this should provide correct restraints.
Contacts.cnd
Code:
dist 7.0
1 1 5
1 15 20
PS. Remember the quality of the results from EOM depend upon the correctness of the model used. An IDP model will give a poor fit if there is significant globular structure. EOM with a completely IDP chain will produce few models that are as compact as a globular domain in addition to an IDP region.
Best regards,
Mark