Magnetic Alignment of Polymer Macro‐Nanodiscs Enables Residual‐Dipolar‐Coupling‐Based High‐Resolution Structural Studies by NMR Spectroscopy

Abstract

Experimentally measured residual dipolar couplings (RDCs) are highly valuable for atomic-resolution structural and dynamic studies of molecular systems ranging from small molecules to large proteins by solution NMR spectroscopy. Here we demonstrate the first use of magnetic-alignment behavior of lyotropic liquid-crystalline polymer macro-nanodiscs (> 20 nm in diameter) as an ovel alignment medium for the measurement of RDCs using high-resolution NMR. The easy preparation of macro-nanodiscs,t heir high stability against pH changes and the presence of divalent metal ions, and their high homogeneity make them an efficient tool to investigate awide range of molecular systems including natural products,proteins,and RNA.

Saponins Form Nonionic Lipid Nanodiscs for Protein Structural Studies by Nuclear Magnetic Resonance Spectroscopy

“…For comparison, cytochrome c RDCs measured using polymer nanodiscs rendered R values greater than 0.95 for the same structures. 8 It is likely that higher polydispersity in the saponin nanodiscs resulted in a lower order parameter than that of the polymer nanodiscs and that this lower order parameter caused the measured RDCs to be of a smaller magnitude. The lower correlations then stemmed from RDCs which were small relative to 15 N spectral line widths.…”

“…Correlation R values were obtained from each structure and ranged from 0.78 to 0.85 for high-resolution crystal structures (Figure S9, Table S1). For comparison, cytochrome c RDCs measured using polymer nanodiscs rendered R values greater than 0.95 for the same structures . It is likely that higher polydispersity in the saponin nanodiscs resulted in a lower order parameter than that of the polymer nanodiscs and that this lower order parameter caused the measured RDCs to be of a smaller magnitude.…”

“…For example, discoidal lipid bilayers, called nanodiscs or bicelles, have emerged as exciting systems to replicate a cell membrane environment for reconstitution of membrane proteins. , Their flat surfaces model the cell membrane surface better than highly curved vesicles or micelles, and their optical transparency allows their use in a wide variety of biophysical and spectroscopic techniques. Additionally, because many nanodisc systems can be spontaneously aligned in a magnetic field, they enable the measurement of residual dipolar couplings (RDCs) by solution NMR experiments for structural characterizations of biomolecules, such as lipid membranes, soluble proteins, and nucleic acids. − …”