Chemical shifts

Use of the chemical shifts file

List of attributes

The following attributes are present in the file:

• "shift_assignment_method" ('STEREO_SPECIFIC', 'FLOATING', 'EQUIVALENT') defines how the hydrogens are merged to produce the spins. 'EQUIVALENT' means that the group of hydrogen is replaced by one spin and is used for  group_type attribute 'METHYL' or NTERMINUS' in the molecule xml file. 'FLOATING' means that the restraint includes one of the two hydrogen in the spin system. 'STEREO_SPECIFIC' means that the two hydrogens are separated. 
  
• 'averaging_method' (NONE,FAST) is not active now.
  
• 'segid' is the chain id of the chain in which the atom is located. 'residue' is the residue number, and 'name' is the atom name.
  
• 'value' is the chemical shift value, and 'error' is the uncertainty on this value.
  

Example of file

Here is an example of the content of chemical shifts xml file:

<!DOCTYPE chemical_shift_list SYSTEM "chemical_shift_list1.0.dtd">
<chemical_shift_list>
  <shift_assignment method="STEREO_SPECIFIC"> 
   <spin_system averaging_method="NONE"> 
     <atom segid="    " residue="90" name="N"/>
     <chemical_shift value="116.88" error="0.0"/>
   </spin_system> 
  </shift_assignment> 
  <shift_assignment method="STEREO_SPECIFIC">
   <spin_system averaging_method="NONE">  
    <atom segid="    " residue="90" name="H"/> 
    <chemical_shift value="8.017" error="0.0"/> 
   </spin_system> 
  </shift_assignment> 
  <shift_assignment method="STEREO_SPECIFIC"> 
   <spin_system averaging_method="NONE">
     <atom segid="    " residue="90" name="HA"/> 
     <chemical_shift value="4.457" error="0.0"/> 
   </spin_system> 
  </shift_assignment> 
  <shift_assignment method="STEREO_SPECIFIC">
   <spin_system averaging_method="NONE">
    <atom segid="    " residue="90" name="HG"/> 
    <chemical_shift value="" error="0.0"/>
   </spin_system>
  </shift_assignment>
  <shift_assignment method="FLOATING"> 
    <spin_system averaging_method="NONE"> 
      <atom segid="    " residue="91" name="HG2"/> 
      <chemical_shift value="1.977" error="0.001"/> 
      <chemical_shift value="" error="0.0"/>
    </spin_system> 
    <spin_system averaging_method="NONE"> 
      <atom segid="    " residue="91" name="HG3"/> 
      <chemical_shift value="1.977" error="0.001"/> 
      <chemical_shift value="" error="0.0"/> 
    </spin_system>
  </shift_assignment>
  <shift_assignment method="FLOATING">
    <spin_system averaging_method="NONE">
      <atom segid="    " residue="91" name="HB2"/>
      <chemical_shift value="2.388" error="0.001"/>  
      <chemical_shift value="2.451" error="0.004"/>
    </spin_system>
    <spin_system averaging_method="NONE">
      <atom segid="    " residue="91" name="HB3"/> 
      <chemical_shift value="2.388" error="0.001"/>
      <chemical_shift value="2.451" error="0.004"/>
    </spin_system>
   </shift_assignment>
   <shift_assignment method="STEREO_SPECIFIC">
    <spin_system averaging_method="NONE"> 
      <atom segid="    " residue="91" name="C"/>
      <chemical_shift value="" error="0.0"/> 
    </spin_system>
   </shift_assignment>
   <shift_assignment method="EQUIVALENT">  
    <spin_system averaging_method="FAST">
      <atom segid="    " residue="82" name="HB1"/>
      <atom segid="    " residue="82" name="HB2"/>
      <atom segid="    " residue="82" name="HB3"/> 
    <chemical_shift value="1.482" error="0.002"/> 
   </spin_system>
  </shift_assignment>
.....