! Common cations parameters for CHARMM (optimized from free energy simulations)
! November 2002


!                 Epsilon         Rmin/2
!                 (kcal/mol)      Angstrom
 
 
SOD      0.0       -0.0469    1.36375
                   ! sodium
                   ! D. Beglovd and B. Roux, dA=-100.8 kcal/mol

POT      0.0       -0.0870    1.76375
                   ! potassium
                   ! D. Beglovd and B. Roux, dA=-82.36+2.8 = -79.56 kca/mol

CLA      0.0       -0.150      2.27
                   ! chloride
                   ! D. Beglovd and B. Roux, dA=-83.87+4.46 = -79.40 kcal/mol
 
RUB      0.0000    -0.15      1.90
                   ! Rubidium
                   ! delta A with respect to POT is +6.0 kcal/mol in bulk water

CES      0.0000    -0.190     2.100
                   ! Cesium
                   ! delta A with respect to POT is +12.0 kcal/mol
 
MG       0.0       -0.0400    1.10000
 
CAL    0.000000  -0.120000     1.3670000 
                   ! Calcium
                   ! S. Marchand and B. Roux, dA = -384.8 kcal/mol
 
CAD    0.000000  -0.120000     1.3570000 
                   ! Cadmium
                   ! S. Marchand and B. Roux

MG       0.0       -0.0400    1.10000



NBFIX
!              Emin         Rmin
!            (kcal/mol)     (A)

                                      !  Free energy relative          Interaction with 
                                      !  to modified K+                isolated NMA
SOD     O     -0.07502      3.245     !  adjusted to yield same         -28.1
                                      !  dA as SOD in liquid 
                                      !  water (21 kcal/mol)

                                      !  Elec free energy              Interaction with
                                      !  in liquid NMA                 isolated NMA
POT     O     -0.1021763     3.69     !  adjusted to yield same         -21.0
                                      !  as POT in liquid
                                      !  water (-82.0 kcal/mol)             

                                      !  Free energy relative 
                                      !  to K+ in liquid NMA
RUB     O     -0.1341641     3.82     !  +6.2