Details

Autor(en) / Beteiligte

• Kelly, John E.
• Chrissian, Christine
• Stark, Ruth E.

Titel

Tailoring NMR experiments for structural characterization of amorphous biological solids: A practical guide

Ist Teil von

• Solid state nuclear magnetic resonance, 2020-10, Vol.109, p.101686-101686, Article 101686

Ort / Verlag

Elsevier Inc

Erscheinungsjahr

2020

Quelle

ScienceDirect

Beschreibungen/Notizen

• Many interesting solid-state targets for biological research do not form crystalline structures; these materials include intrinsically disordered proteins, plant biopolymer composites, cell-wall polysaccharides, and soil organic matter. The absence of aligned repeating structural elements and atomic-level rigidity presents hurdles to achieving structural elucidation and obtaining functional insights. We describe strategies for adapting several solid-state NMR methods to determine the molecular structures and compositions of these amorphous biosolids. The main spectroscopic problems in studying amorphous structures by NMR are over/under-sampling of the spin signals and spectral complexity. These problems arise in part because amorphous biosolids typically contain a mix of rigid and mobile domains, making it difficult to select a single experiment or set of acquisition conditions that fairly represents all nuclear spins in a carbon-based organic sample. These issues can be addressed by running hybrid experiments, such as using direct excitation alongside cross polarization-based methods, to develop a more holistic picture of the macromolecular system. In situations of spectral crowding or overlap, the structural elucidation strategy can be further assisted by coupling 13C spins to nuclei such as 15N, filtering out portions of the spectrum, highlighting individual moieties of interest, and adding a second or third spectral dimension to an NMR experiment in order to spread out the resonances and link them pairwise through space or through bonds. We discuss practical aspects and illustrations from the recent literature for 1D experiments that use cross or direct polarization and both homo- and heteronuclear 2D and 3D solid-state NMR experiments. [Display omitted] •Structure elucidation is challenging for amorphous biomacromolecular solids.•Noncrystalline biological complexes can be studied structurally by solid-state NMR.•Solid-state NMR can distinguish mobile from rigid structures in biological solids.•Multidimensional solid-state NMR improves structural information for biosolids.•Solid-state NMR reveals molecular structure in microbial cells and plant polymers.