[Babcock_Hall]

We are reading some papers in which a pseudodihedral angle was defined for four consecutive C-alpha atoms.  In the work we have seen so far the angles fall approximately between 0° and 110°; however, we are working on a related protein for which we believe we are seeing some negative values.  That made me realize that I am unsure how positive or negative values are assigned with respect to pseudodihedral angles.  I found this paper, but their values go from 0 to 360°.
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2142948/pdf/7833816.pdf