Base pairing at PolyA, ψ, and lower PBS is intramolecular. (A) NOE strips of A2rGrCr and A2:Ar 5′-L344 samples focusing on A66-H2 proton (located in the base of the PolyA hairpin). In the mixed sample, A66-H2 does not give an NOE to the cross-strand A96-H1′, providing evidence that the base pairing at the base of PolyA is intramolecular. (B) NOE strips of A2rGrCr and A2:Ar 5′-L344 samples focusing on A314 and A324-H2 protons. In the mixed sample, A314-H2 does not give an NOE to the cross-strand A324-H1′. Likewise, A324-H2 does not give an NOE to the cross-strand A314-H1′. These data are consistent with intramolecular base pairing in the ψ hairpin. (C) NOE strips of A2rGrCr and A2:Gr 5′-L344 samples focusing on A220-H2 proton. In the mixed sample, A220-H2 does not give an NOE to the cross-strand G129-H1′, providing evidence that the base pairing at the lower stem of PBS is intramolecular.