I have a few questions related to a 3.5 angstrom structure. I have one helix that I am having trouble placing accurately. It does have a cysteine that disulfide bonds with the same residue in a symmetry related molecule. Can I restrain this distance during a rigid body refinement of the helix? How do I do this? What kind of parameters would be appropriate for the disulfide?

My second question is whether someone can suggest appropriate distance_ideal,    sigma, and  slack for hydrogen bond restraints for a helix? Also, I have a 2 angstrom structure of this part of the complex for reference.

Thanks!
Kendall Nettles