Dihedral angles - how to calculate

[Andrew Martin]

web-server-account (web at pcjfn.msc.com) wrote:
: George A. Heavner (gheavner at voicenet.com) wrote:
: : I am working on a project where I have cartesian coordinates for four
: : consecutive atoms and need to calculate the dihedral angle (with correct
: : sign).  I am not a crystallographer and readily admit to difficulty with
: : the math.  The magnitude is not difficult (angle between two planes) but
: : I am stuck on the sign.  Can anyone provide me with the procedure or
: : point me to a readily intelligible text or other source.

Didn't see the original posting, but you can use my torsions
program available via my web page :-)


Best wishes,

Andrew