X-PLOR and Hemoglobin

[Darin Scott Katz]

Hi,

I'm hoping someone can help me.  I'm trying to refine data I've collected on 
some hemoglobin crystals with X-PLOR (v 3.1).  I run into problems when I
do a "check" on the tetramer.  I consistently get an error message saying I
have "linear bond angles" in my structure.  However, when I use the alpha-
beta dimer only, I get no such error.

Has anyone had similar experiences with refining multi-subunit structures 
with X-PLOR?  I believe my problem arises when I introduce the other dimer
into the check model.  If anyone could be of help, I'd be most appreciative.

Thanks,

Darin Katz