Syntax

  PCSA {<Pseuso-Chem-Shift-Anis-statement>} END 
  <PCSAnisotropy-statement>:== 
   ASSIgn <selection> <selection> <selection> <selection> 
   <selection> <selection> <selection> 
   <real> <real> <real>
   {* atom i atom j atom k atom l 
    ! atom m atom n atom o 
    ! PCSA-obs  PCSA-err-min PCSA-err-plus *}
   {* atom i = center, atom j = Z, atom k = X, atom l = Y *}
   {* atom m defines the central atom *}
   {* atoms n and o define the at1 and at2 *}
   {* The unit for PCSA in the constraint file is ppb *}
   CLASsification <name> ! Starts a new class. Applies to all 
        ! ASSIgn , TYPE, and FORCe entries until 
        ! another CLASS entry is issued. 
   SCALe <real> for normalizing the alignment tensor
   {* Use the static dipolar coupling (in Hz) for the nuclei 
    ! used to calculate Da 
    ! DNH(r=1.04A) = 21652.1 ; DCH (r=1.08A) = 47965.1 *}
   COEFficient <real> <real> <real>
   coef: <DFS> <Da in Hz> <rhombicity>
   SIGMa <real> <real> <real>
   CSA sigma <d11> <d22> <d33> <theta>
   CSA tensor in ppm for A-form RNA or B-form DNA base carbons
   d33 is orthogonal to the base plane
   theta is the angle in degrees between d11 and heavy atom bisector
        !                       d11   d22     d33  theta
        ! for C2:A   DNA/RNA   89.0  15.0  -104.0   -2.0
        ! for C5:C/U DNA/RNA   82.0   2.0   -85.0   -5.0
        ! for C6:C   DNA       96.0  19.0  -115.0   28.0
        ! for C6:T   DNA       97.0  -1.0   -96.0   29.0
        ! for C6:C/U     RNA  125.0  -7.0  -119.0   29.0
        ! for C8:A   DNA/RNA   74.0   5.0   -79.0   32.0
        ! for C8:A   DNA/RNA   80.0   5.0   -85.0   32.0
   FORCeconstant <real> ! force constant for all 
        ! assignments in the current class. {default = 0.010} 
   NREStraints <integer> ! number of slots for CSAnisotropy 
        ! restraints to allocate in memory {default = 200} 
   POTEntial <SQUAre | HARMonic> ! whether to use CSA-err or not
   PRINt THREshold <real> ! prints CSAnisotropy violations 
        ! greater than the specified value 
   RESEt  ! erases the CSA. assignment table, but keeps 
        ! NREStraints the same.