Complex Formation of the Tetracycline‐Binding Aptamer Investigated by Specific Cross‐Relaxation under DNP

Abstract

Abstract While dynamic nuclear polarization (DNP) under magic‐angle spinning (MAS) is generally a powerful method capable of greatly enhancing the sensitivity of solid‐state NMR spectroscopy, hyperpolarization also gives rise to peculiar spin dynamics. Here, we elucidate how specific cross‐relaxation enhancement by active motions under DNP (SCREAM‐DNP) can be utilized to selectively obtain MAS‐NMR spectra of an RNA aptamer in a tightly bound complex with a methyl‐bearing ligand (tetracycline) due to the effective CH 3 ‐reorientation at an optimized sample temperature of approximately 160 K. SCREAM‐DNP can spectrally isolate the complex from non‐bound species in an RNA mixture. This selectivity allows for a competition assay between the aptamer and a mutant with compromised binding affinity. Variations in molecular structure and methyl dynamics, as observed by SCREAM‐DNP, between free tetracycline and RNA‐bound tetracycline are discussed.