ECOSY NMR spectrum of the single-stranded RNA
5′-GU(2′-SCF3-U)CG. For the 2′-SCF3 uridine moiety, the
3-bond scalar coupling constant of H1′ and H2′ (3JH1′-H2′) was extracted from
the corresponding crosspeak and amounted to 10.4 Hz. Assuming a pure
C2′/C3′-endo equilibrium, this value is correlated to
a C2′-endo (South) population of 100%.29,30 For the other single-stranded RNA nucleotides, coupling constants
of 8.5 to 9.0 Hz were measured corresponding to C2′-endo populations
between 84 to 89%. Conditions: cRNA =
0.3 mM; 25 mM sodium cacodylate, pH 7.0, 298 K.