Labelling CG atoms in VAL and PHE?

Gerard Kleywegt gkleyweg at
Sat Jun 1 12:05:45 EST 1996

Gerard Pujadas wrote:
>         My name is Gerard Pujadas and I'm doing studies about protein
> conformation. I would like to know which criteria uses the crystallographs
> to distinguish between the carbons in the G position of their side chain.

sidechains with chemically indistinguishable atoms (such as phe cd1/2, ce1/2
and asp od1/2) are named such that the chi torsion (defined w.r.t. the "1"
atom) has a value in between -90 and +90
however, the rules say that these assignments may change over the course
of a refinement (e.g., if a ring is flipped) and that this is acceptable


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