REMARKS  zinc and such,... 

MASS   S     32.06000! sulphur
MASS   ZN    65.3700 ! ZINC 
MASS   MG    24.30500
                    
remarks  to use it specify the following patch command: (after all four
remarks  CYS have been generated
remarks  PATCH ZN  reference=1=( atom a 20 * ) 
remarks            reference=2=( atom b 30 * )
remarks            reference=3=( atom a 11 * )
remarks            reference=4=( atom b 22 * )
remarks   END

PRESidue ZNK     { disulfide bridge  ...CYS      CYS...
                                              \DISU/            }
 GROUP     
  MODIfy ATOM 1CB           CHARge= 0.19  END
  MODIfy ATOM 1SG  TYPE=S   CHARge=-0.19  END
  ATOM 1ZN         TYPE=ZN  CHARGE=+2.0 END
 GROUP
  MODIfy ATOM 2CB           CHARge= 0.19  END
  MODIfy ATOM 2SG  TYPE=S   CHARge=-0.19  END
 GROUP
  MODIfy ATOM 3CB           CHARge= 0.19  END
  MODIfy ATOM 3SG  TYPE=S   CHARge=-0.19  END
 GROUP
  MODIfy ATOM 4CB           CHARge= 0.19  END
  MODIfy ATOM 4SG  TYPE=S   CHARge=-0.19  END

 ADD BOND 1ZN 1SG
 ADD BOND 1ZN 2SG
 ADD BOND 1ZN 3SG
 ADD BOND 1ZN 4SG

 ADD ANGLe  1CB 1SG 1ZN 
 ADD ANGLe  2CB 2SG 1ZN 
 ADD ANGLe  3CB 3SG 1ZN 
 ADD ANGLe  4CB 4SG 1ZN 
 ADD ANGLe  1SG 2SG 1ZN
 ADD ANGLe  1SG 3SG 1ZN
 ADD ANGLe  1SG 4SG 1ZN
 ADD ANGLe  2SG 3SG 1ZN
 ADD ANGLe  2SG 4SG 1ZN
 ADD ANGLe  3SG 4SG 1ZN

END {DISU}


RESIdue ZN   {* zinc *}
 GROUP     
  ATOM ZN         TYPE=ZN  CHARGE=+2.0 END
END

RESIdue MG         
 GROUp
  ATOM MG  TYPE=MG    CHARGE=2.0    END
END {MG}