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Hi all,
I am using SHELX to refine a protein structure where electron density
clearly shows what appears to be a rather strong CH - O hydrogen bond
between two residues (i.e. Met and Asp are within 2.5A of one
another). However, SHELX seems to interpret that as a steric clash
and the two residues are pushed apart (and out of density) in the
refinement. I'm trying different things to convince SHELX that those
atoms indeed belong this close together, but I'd like to ask the pros
for ideas, as well. I would prefer to avoid fixing the coordinates
of the residues, and using BIND to simulate covalent connectivity
between those atoms also seems like a misrepresentation of the
situation. So, is there a way to manually specify an individual
hydrogen bond in SHELX, rather than let the program find it? I can't
find anything about that in the manual. Alternatively, is there a
way to selectively turn off the anti-bumping restraints for a group
of atoms? I seem to remember a brief discussion on the matter in
this forum, and the answer appears to be "no", but I thought I'd ask
anyway.
Thanks!
Art
