For PELDOR measurements four different constructs with two spin labels each were prepared: G29/G36 within stem 2 and the corresponding hairpin (blue), C14/C44 located in the region between the pseudoknot and stem 1 (green), A9/A49 across stem 1 and the 3' end of the RNA (magenta), and C4/C17 across the pseudoknot (red, Fig. and Fig. ).