As the PDB file contains no isotope information, this needs to now be specified. First click on the ``X isotope'' button to set the nuclear isotope type of the heteronuclei:
As nitrogen relaxation is being studied, the nuclear isotope name can be left as ``15N'' and the spin ID string to ``@N*''. Therefore simply click on the ``Ok'' button. Exactly the same procedure can be used for the proton with the ``H isotope'' button.