anchor.diff:       if (i==equilibration_loops) sampling = .true.
        if (modulo(i,64) == 0) write(*,'(i05)',advance='no') i
        md_loop: do j = 1, N_MD_steps
  -        current_time = (i*N_MD_steps + (j-1))*dt
           call md_pos(solvent, dt)
           do k=1, colloids% Nmax
              colloids% pos(:,k) = colloids% pos(:,k) + dt * colloids% vel(:,k) + &
  
positive.code:     colloids%mass(enz_2) = colloids%mass(enz_2) + 1
  
      bound_molecule_id(enzyme_idx) = solvent%id(idx)
      solvent%species(idx) = 0
  
      ! compute conformational energy difference when changing the angle
  
negative.code:           s_sp = solvent%species(m)
  
            ! skip neutral fluid particles
            if ((s_sp == 0) .or. (s_sp == 3)) cycle select_loop
  
            dist = norm2(rel_pos(x_enzyme, solvent%pos(:,m), solvent_cells%edges))
  
  