To gain further insights into the dynamic properties of the ssRNA at pico-to nanosecond timescales, we measured longitudinal (R 1 ) and transverse (R 2 ) carbon relaxation data for the nucleobases (C2 C6 C8) using 2D 13 C relaxation R 1 and R 1r NMR experiments (40) , where R 1 and R 2 values are determined using in-house software (Supplementary Figure S4) . These measurements represent the first nucleobase 13 C relaxation measurements performed on a ssRNA. The measured R 1 and R 2 values were used to compute order parameters (51) using S 2 = (2R 2 -R 1 ) (60), and normalized to yield a relative order parameter (S 2 rel ) describing the relative degree of order within a molecule ranging from 0 to 1, where 0 and 1 represent minimum and maximum order, respectively. The S 2 rel values were normalized against central residues A31 (C8) and C33 (C6). Resonance overlap prevented the normalization of C2 spins. Again, we observe a gradual reduction in S 2 rel indicating higher levels of disorder moving from central polyadenine residues (A28-C33) towards the terminal ends ( Figure 2B ).