[gmx-users] calcium parameters

[Mahnam]

 In God we trust
Hi GMX-users
I want to do MD simulations of amylase which has 3 ca2+ ions  by Gromacs 
4.5.3 and charm22 force field.
I don’t want to  restraints calcium and I searched mailing list and papers 
for Ca+2 binding parameters in Charm22 but I only found binding parameters 
for ca-oxygen (in this paper :New Force Field for Calcium Binding Sites in 
Annexin–Membrane Complexes) , would you please tell me angle  parameters 
of Ca-OD1-CG, Ca-O-C, OD2-Ca-O, OD1-Ca-OD1, and dihedral parameters that 
contains OD1-Ca, Ca-O in middle of dihedral, if it is possible.(OD1= 
carboxyl, O= carbonyl oxygen)
Of course I will correct charge of Ca+2 and its ligands according to lensink 
thesis for charge transfer effects.

Thank you very much in advance.
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