disulfide bonds too long

[Triss Elkins]

I have done a molecular replacement with a model in which there are
several disulfide
bonds that are too long - from 2.2 to 2.5A.  I am refining with CNS and
have defined
these as disulfides in generate.inp.  In modeling, by selecting a
favored rotamer conformation for
each cysteine, I end up with disulfide bonds that are about 2.0A but in
refinement the
bond length always increases.  If I increase wa substantially, the bond
lengths do stay
closer to 2.0 but geometry overall is too loose.  Anyone have an idea
how to deal with this?

Trissa Elkins


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