[gmx-users] question about dihedral constraints

[Tom]

Dear Gromacs Users,

I want to use dihedral constraint in gmx.

I directly type the following onto my  topol.top file :
--------------------------------------
[ dihedral_restraints ]
; ai   aj    ak    al  type  label  phi  dphi  kfac  power
; phi C'(n-1) - N - CA - C'
   506    505     502    503     1      1  180     0     1      2
--------------------------------------

Do I also need to add these to *mdp file?
---------------------------------------
dihre                     = yes
dihre_fc                  = 15000
-------------------------------------
Because I only need to contraint some of the dihedrals,
I will  not constraints all of them.
If I add the above on  *mdp file, will all the dihedrals be constrainted?

Another quesiton is what is the format of this dihedral constraints
on *rtp file? How about the angle constraints? That would save a lot
of work if pdb2gmx can automatically add these constraints to *top file.

Thanks a lot for the help!

Steven