[gmx-users] Topology for pyroglutamic acid

[Lieven Buts]

  In one of the proteins I am looking at the N-terminal
glutamine residue has undergone cyclisation to pyrrolidone
carboxylic acid (PCA), also known as pyroglutamate (PGA):

        O
        "                          CH2-CH2
    H2N-C-CH2-CH2                  |   |
              |          --->    O=C   CH-C-...
          H2N-CH-C-...              \ /   "
                 "                   N    O
                 O                   |
                                     H


  According to Creighton, this is a common rearrangement
for N-terminal glutamines.

  For the time being I am using an unmodified glutamine
for my GROMACS model, and I don't think this difference
is very important in the overall picture, but I was wondering
about the best way to represent this in GROMACS.


-- 
Lieven Buts
Vrije Universiteit Brussel