Oral Session 1
Monday, March 29, 2021 | 13:00-14:30 EDT | Go to About Oral Sessions to learn more about the session format.
Session Chair: Joanna Long (NHMFL, University of Florida)
Invited Speakers & Abstracts
Relaxation dispersion techniques in fast MAS solid-state NMR
Recent advances in instrumentations, isotope-labeling schemes, and the continued method developments for fast magic-angle-spinning (MAS) applications can provide unprecedented insights into biologically relevant structural dynamics of large protein complexes or insoluble biomacromolecules. The importance of microsecond time-scale conformational exchange in protein-protein interaction, allostery, or signal transduction is widely recognized and extensively studied with solution-state spin relaxation dispersion techniques, but the implementation of the corresponding solid-state relaxation methods is still lagging. In this talk, I summarize the theoretical aspects, practical implementations, and remaining challenges of solid-state rotating-frame relaxation dispersion experiments focusing on the Near-rotary Resonance Relaxation Dispersion (NERRD) technique that is particularly sensitive to fast microsecond structural transitions.
Base-Pair Switch Modulates microRNA activity
MicroRNAs regulate messenger RNA translation via Argonaute (hAgo2). The seed (Watson-Crick base pairing) governs target selection and repression efficiency, however, structural and dynamic information is scarce. We reveal, using 1H, 13C and 15N R1ρ Relaxation Dispersion, a base pair switch in the miRNA–mRNA duplex, which elongats the seed and increases down regulation efficiency (by cellular assays) in an invisible, low-populated state. In combination with molecular simulations, structural and dynamic features of the miR-34a mRNA of Sirt1 (regulator of P53 and cancer gatekeeper RNA) were elucidated and a more general structural switch motif was revealed. Reference: Baronti, Guzzetti, Ebrahimi, Friebe Sandoz, Steiner, Schlagnitweit, Fromm, Silva, Fontana, Chen and Petzold Nature 2020
Fast NMR with fast MAS (without and with DNP)
Fast magic-angle spinning narrows spectral resonances better than Brownian motion does for solution NMR, removing a fundamental barrier to the NMR study of large systems with <sup>1</sup>H detection. Nonetheless, performing the assignment of all resonances remains a rate-limiting step in protein structural studies, and even the latest optimized protocols fail to perform this step when the protein size exceeds ∼20 kDa. We introduce two approaches that address this issue, simultaneous parallel detection and projection spectroscopy of hyperdimensional datasets, allowing accelerated acquisition and data analysis and at the same time lifting the molecular size barrier of the targets amenable to NMR analysis. We additionally discuss the applicability of these methods under cryogenic conditions to perform backbone sequential assignments directly with DNP.