Hello Jian--
> We are calculating the structure of a membrane peptide with two
> helices linked with a loop with PISEMA data (chemical shift, dipolar
> coupling) with dihedral angle? hydrogen bond restraints for the
> helical part, we also have some distance restraints for atoms from
> both helices.
>
> From PISEMA experiment we expect to get models with the right tilt
> angle with respect to the membrane normal (i.e., the z-axis), but we
> got models with a variety of tilt angles. For example, we expect to
> have a tilt angle of 12 to 17 degrees, but some of the models have
> tilt angle that is 26, which is way too large.
> I'm wondering what are the factors that determine the tilt angle of
> the peptide in XPLOR calculation.
Are your restraints well-satisfied? There may be some problem such
that there are large violations causing convergence problems. If your
PISEMA-based restraints are satisfied, then the tilt angle should be
correct. No?
best regards--
Charles
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--
Charles Schwieters email: Charles at Schwieters.org
www: http://schwieters.org/cds
phone: (301) 402-4914 PGP key: http://schwieters.org/cds/pgp.txt
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