As the relaxation data is at the level of the spins, the molecule, residue and spin data structures need to be set up. In the R1 and R2 GUI analysis tabs, there is a special “Spin systems” GUI element designed for this. This will initially say “0 spins loaded and selected”. Click on the “Spin editor” button to launch the spin viewer window. The steps for setting up the spin containers using PDB files are described in section 4.5.2 on page or for sequence files in section 4.5.3 on page .