remark   file par_zinc.pro  version 0.4  date 19-mar-97
remark   Geometric energy function parameters for zinc finger (also finger2)
remark   Author: Jurgen F. Doreleijers, RUU
remark   rev 0.2  angles CRH  NR ZN 120 -> 126
remark   rev 0.3  NONBonded  ZN 
remark   rev 0.4  included parameters for ND1 coordination
remark   rev 0.5  changed angle ( CH2E SH1E ZN ) to 100 degree and 
remark            introduced variables for the force constants.
remark   rev 1.0  changed angle ( CH2E SH1E ZN ) to 105 degree unlike 
remark            Neuhaus et al., J Mol Biol 228 (2): 637-651 but like
remark            Clarke and Yuan, Proteins 23 (2): 256-263.

                                             {* set energy constants *} 
evaluate ($kbon =  1000)  ! normal = 1000 kcal / mol-A^2
evaluate ($kang =  500)  ! normal = 500  kcal / mol-rad^2
evaluate ($kchi =  500)  ! normal = 500  kcal / mol-rad^2

SET ECHO=FALSE END

   bonds SH1E  ZN  $kbon 2.30                 
   bonds NH1   ZN  $kbon 2.00               
   bonds NR    ZN  $kbon 2.00                 {* For ND1 coordination *}  

   angles SH1E ZN SH1E    $kang 109.5                   {* Pure tetrahedral *}
   angles SH1E ZN NH1     $kang 109.5

   angles NH1  ZN NH1     $kang 109.5
   angles CH2E SH1E ZN    $kang 105.0                  {* CHECK !! *}

   angles CRH  NH1 ZN     $kang 126.0                    
   angles CR1E NH1 ZN     $kang 126.0                    
   angles C5   NH1 ZN     $kang 126.0                    

   angles NH1  ZN NR      $kang 109.5          {* For ND1 coordination *}

   angles SH1E ZN NR      $kang 109.5
   angles NR   ZN NR      $kang 109.5

   angles CRH  NR ZN      $kang 126.0                    
   angles CR1E NR ZN      $kang 126.0                    
   angles C5   NR ZN      $kang 126.0                

   improper NR CRH  NH1 ZN     $kchi  0 180.0 
   improper C5 CR1E NH1 ZN     $kchi  0 180.0 
   improper C5 CR1E NR  ZN     $kchi  0 180.0                  {* Redundant ? *}

   improper CR1E C5   NR ZN     $kchi  0 180.0
   improper CH2E C5   NR ZN     $kchi  0 180.0
   improper NH1  CRH  NR ZN     $kchi  0 180.0


   improper NR NR SH1E SH1E       $kchi  0 -70.0


 ! from: http://xplor.csb.yale.edu/xploron-web/toppar/parameter.elements
 !                  eps     sigma       eps(1:4) sigma(1:4) 
 !                  (kcal/mol) (A)
 !                  ---------------------------------------
  NONBonded  ZN      .2500  1.942        .2500   1.942
 ! 
   nbonds                                    {*This statement specifies the*}
      atom cdie shift eps=1.0  e14fac=0.4    {*nonbonded interaction energy*}
      cutnb=7.5 ctonnb=6.0 ctofnb=6.5        {*options.  Note the reduced  *}
      nbxmod=5 vswitch                       {*nonbonding cutoff to save   *}
   end                                       {*CPU time.                   *}


SET ECHO=TRUE END