Our study shows that ssRNA can exhibit complex conformational behavior, including variable levels of stacking and propensities to form an A-form helical conformation across the polynucleotide chain, and also, the ability to interrupt stacked residues by introducing sequence-specific kinks and/or distortions. While it has been known for some time that polyadenine stretches tend to stack and form helical conformations (13, 14, 16, 18, 37) , the details of this helical geometry were difficult to decipher based solely on NOE-based NMR data. Our RDC measurements on the ssRNA, together with scalar coupling constant measurements, strongly suggest that the polyadenine tract forms an A-form-like conformation in the WT ssRNA. Our results also unveil dynamic complexity in ssRNA, including a gradual increase in disorder occurring towards the terminal ends that is reminiscent of unfolded polypeptide chains (74) , and also, slower sequence-specific dynamics occurring at micro-to millisecond timescales that may involve transient stacking/unstacking motions that may result in kinking of the ssRNA. Altogether, our studies show that 'structured' ssRNA exhibits exquisite quality spectra and can be studied quantitatively using NMR-based structure and dynamics measurements.