[gmx-users] help with orientation restraints

[Hanin Omar]

Hi all;I am an amateur gromacs user, but i have read all the tutorials i could find on how to perform md simulations using gromacs, however i still cant find any tutorial about how to include orientation restraints in my simulations. i want to perform a simulation on a helical protein and include 4 types of RDC data from two experiments. In the manual their is an example with N-H RDC data, however  i need the constant ci for other types of RDC's ( C-N, C-H, Calpha-Halpha) does anybody know how to calculate them or where can i find them? also this is an example of the itp file that contains my RDC value:[ orientation_restraints ]
;  ai    aj    type   exp.    label   alpha   const.   obs.   weight
;                                        Hz     nm^3     Hz    Hz^-2
;residue 2  
   20     21      1      1        1       3    6.083   7.72483   1.0 
   20     21      1      2        2       3    6.083   7.27571   1.0
;residue 4 
   46     47      1      1        3       3    6.083   1.864475  1.0 
   46     47      1      2        4       3    6.083   -14.2043  1.0 
;residue 5
   66     67      1      1        5       3    6.083   10.16845  1.0 
   66     67      1      2        6       3    6.083   -11.278   1.0 
and in the topology file i added this:
; Include 1a1z protein topology
#include "1a1z.itp"

; Include Orientation restraint file
#ifdef POSRES
#include "ocNH.itp"
#endif
and then in my mdp files for the minimization, equiliberation and md i have this:
define        = -DPOSRES    ; restrain the protein

are these steps correct ??????thank you for your helpHanin Omar