Orientation relationship

Naiming Chu zu04117 at uabdpo.dpo.uab.edu
Tue Feb 13 11:25:18 EST 1996


Experts:

I am working on a dimer structure which has 1,2 molecules in asymmetry 
unit. Its space group is P21.

Now I am applying (-x,y+1/2,-z) onto 1,2 then get 1',2'. I expect the 
rotation angle between 1' and 2 should be the same as 1,2.

I use xplor to do the above operation.

I load 1 and 2 pdb file seperately, then do:
 coor fit end

the out put is like this:

Spherical polar angle: 85.2725 27.095 180.9102(kappar)
Rotation angle 179.0898 at -0.8872 -0.0824 0.4539

Ok, now I load 1 then:

coor fractionalize

coor rotate  ( -1  0  0 )
             (  0  1  0 )
             (  0  0 -1 )
coor translate (0 0.5 0)
coor orthogonalize
coor write

I get 1' pdb file.

then load 1' and 2 file, do coor fit, get the output:

Spherical polar angle: 90.4567 117.0950 189.4547(kappar)
Rotation angle 170.5453 about axis 0.4555 0.0080 0.8902

My question is why the rotation angles are not same before and after 
symmetry operation?

Would be grateful for any comment!

Naiming



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