subroutine sc_minimize(etot,iretcode,nfun)
c     Minimizes side-chains only, leaving backbone frozen
crc      implicit none

c     Includes
      implicit real*8 (a-h,o-z)
      include 'DIMENSIONS'
      include 'COMMON.VAR'
      include 'COMMON.CHAIN'
      include 'COMMON.FFIELD'

c     Output arguments
      double precision etot
      integer iretcode,nfun

c     Local variables
      integer i
      double precision orig_w(n_ene),energy(0:n_ene)
      double precision var(maxvar)


c     Set non side-chain weights to zero (minimization is faster)
c     NOTE: e(2) does not actually depend on the side-chain, only CA
      orig_w(2)=wscp
      orig_w(3)=welec
      orig_w(4)=wcorr
      orig_w(5)=wcorr5
      orig_w(6)=wcorr6
      orig_w(7)=wel_loc
      orig_w(8)=wturn3
      orig_w(9)=wturn4
      orig_w(10)=wturn6
      orig_w(11)=wang
      orig_w(13)=wtor
      orig_w(14)=wtor_d

      wscp=0.D0
      welec=0.D0
      wcorr=0.D0
      wcorr5=0.D0
      wcorr6=0.D0
      wel_loc=0.D0
      wturn3=0.D0
      wturn4=0.D0
      wturn6=0.D0
      wang=0.D0
      wtor=0.D0
      wtor_d=0.D0

c     Prepare to freeze backbone
      do i=1,nres
        mask_phi(i)=0
        mask_theta(i)=0
        mask_side(i)=1
      enddo

c     Minimize the side-chains
      mask_r=.true.
      call geom_to_var(nvar,var)
      call minimize(etot,var,iretcode,nfun)
      call var_to_geom(nvar,var)
      mask_r=.false.

c     Put the original weights back and calculate the full energy
      wscp=orig_w(2)
      welec=orig_w(3)
      wcorr=orig_w(4)
      wcorr5=orig_w(5)
      wcorr6=orig_w(6)
      wel_loc=orig_w(7)
      wturn3=orig_w(8)
      wturn4=orig_w(9)
      wturn6=orig_w(10)
      wang=orig_w(11)
      wtor=orig_w(13)
      wtor_d=orig_w(14)

      call chainbuild_extconf
      call etotal(energy)
      etot=energy(0)

      return
      end