Protein dynamics in the solid-state from 2H NMR lineshape analysis. III. MOMD in the presence of Magic Angle Spinning

Abstract

We report on a new approach to the analysis of dynamic NMR lineshapes from polycrystalline (i.e., macroscopically disordered) samples in the presence of Magic Angle Spinning (MAS). This is an application of the Stochastic Liouville Equation developed by Freed and co-workers for treating restricted (i.e., microscopically ordered) motions. The H nucleus in an internally-mobile C-CD moiety serves as a prototype probe. The acronym is H/MOMD/MAS, where MOMD stands for "microscopic-order-macroscopic-disorder." The key elements describing internal motions - their type, the local spatial restrictions, and related features of local geometry - are treated in MOMD generally, within their rigorous three-dimensional tensorial requirements. Based on this representation a single physically well-defined model of local motion has the capability of reproducing experimental spectra. There exist other methods for analyzing dynamicH/MAS spectra which advocate simple motional modes. Yet, to reproduce satisfactorily the experimental lineshapes, one has either to use unusual parameter values, or combine several simple motional modes. The multi-simple-mode reasoning assumes independence of the constituent modes, features ambiguity as different simple modes may be used, renders inter-system comparison difficult as the overall models differ, and makes possible model-improvement only by adding yet another simple mode, i.e., changing the overall model. H/MOMD/MAS is free of such limitations and inherently provides a clear physical interpretation. These features are illustrated. The advantage ofH/MOMD/MAS in dealing with sensitive but hardly investigated slow-motional lineshapes is demonstrated by applying it to actual experimental data. The results differ from those obtained previously with a two-site exchange scheme that yielded unusual parameters.

MOMD Analysis of NMR Line Shapes from Aβ-Amyloid Fibrils: A New Tool for Characterizing Molecular Environments in Protein Aggregates

“…The following comment is in order. Here and in previous studies, 19–21 we present unique MOMD-derived pictures of structural dynamics. This is accomplished by analyzing a sizable set of temperature-dependent 2 H line shapes.…”

Phenyl-Ring Dynamics in Amyloid Fibrils and Proteins: The Microscopic-Order-Macroscopic-Disorder Perspective

“…Recently we developed MOMD for the analysis of 2 H spectra acquired in the presence of Magic Angle Spinning (MAS). 19 Such spectra are better resolved than CW spectra (ref 19 and articles cited therein). Applications of MOMD/MAS are expected to bear out the benefits of enhanced resolution.…”

Montmorillonite nanoclay aggregated in a fractal structure in an acrylic‐styrene matrix, slowed the chain dynamics and increased an order of magnitude the tensile modulus

“…For detecting polymer–nanoclay interactions in the films, solid‐state NMR with magic angle spinning (MAS) was utilized. The fundamental principle is dynamics changes of the polymers due to interactions with nanoclay particles 24 . With MAS, signals from highly mobile portions of the polymer give rise to a strong center band (isotropic chemical shift) with little or no spinning side bands.…”