title: Characterizing slow chemical exchange in nucleic acids by carbon CEST and low spin-lock field R(1ρ) NMR spectroscopy.
abstract: Quantitative characterization of dynamic exchange between various conformational states provides essential insights into the molecular basis of many regulatory RNA functions. Here, we present an application of nucleic-acid-optimized carbon chemical exchange saturation transfer (CEST) and low spin-lock field R(1ρ) relaxation dispersion (RD) NMR experiments in characterizing slow chemical exchange in nucleic acids that is otherwise difficult if not impossible to be quantified by the ZZ-exchange NMR experiment. We demonstrated the application on a 47-nucleotide fluoride riboswitch in the ligand-free state, for which CEST and R(1ρ) RD profiles of base and sugar carbons revealed slow exchange dynamics involving a sparsely populated (p ~ 10%) and shortly lived (τ ~ 10 ms) NMR "invisible" state. The utility of CEST and low spin-lock field R(1ρ) RD experiments in studying slow exchange was further validated in characterizing an exchange as slow as ~60 s(-1).
authors.affiliation: Department of Biochemistry and Biophysics and ‡Department of Chemistry, University of North Carolina at Chapel Hill , Chapel Hill, North Carolina 27599, United States.
authors.forename: Bo
authors.initials: B
authors.lastname: Zhao
authors.forename: Alexandar L
authors.initials: AL
authors.lastname: Hansen
authors.forename: Qi
authors.initials: Q
authors.lastname: Zhang
mesh_terms: D001483:Base Sequence; D002244:Carbon / Q000737:chemistry*; D005459:Fluorides / Q000737:chemistry; D009682:Magnetic Resonance Spectroscopy; D009696:Nucleic Acids / Q000737:chemistry*; D058928:Riboswitch / Q000502:physiology
chemical_list: D009696:Nucleic Acids; D058928:Riboswitch; D002244:Carbon; D005459:Fluorides