[gmx-users] D-aminoacids in OPLS

Guillem Portella gportel at gwdg.de
Wed Mar 16 17:00:40 CET 2005

Dear users,

I'm currently trying to generate a topology for D-aminoacids, namely D-leucine 
and D-valine, using OPLS force field. In ffgmx this was quite 
straightforward. I know that OPLS does not use improper angles for chiral 
center. I cannot find the angle or group of angles that have to be modified 
(and how...), because the chiral center is not directly involved in this 
definitions. Does anybody have a clue?

This is where this angles are defined, e.g. in L-leucine

 [ dihedrals ] ; override some with residue-specific ones
     N    CA    CB    CG    dih_LEU_chi1_N_C_C_C  <-- RB Fourier series coeff.
    CG    CB    CA     C    dih_LEU_chi1_C_C_C_CO        
 [ impropers ]
    -C    CA     N     H    improper_Z_N_X_Y
    CA    +N     C     O    improper_O_C_X_Y

where  #define improper_Z_N_X_Y        180.0      4.18400   2

Thank you very much in advanced,


 Guillem Portella 
 Computational biomolecular dynamics group at the 
 Max Planck Institute for Biophysical Chemistry 
 Am Fassberg 11 
 D-37077 Goettingen -- Germany --
 phone: ++49-551-2012309 
 fax: ++49-551-2012302 
 Email: gportel at gwdg.de 

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