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

Area of Science:

• Biophysical Chemistry
• Materials Science
• Structural Biology

Background:

• Many biologically relevant solid-state materials, including intrinsically disordered proteins and plant biopolymers, lack crystalline structures.
• The absence of ordered structures hinders traditional methods for molecular structural elucidation and functional analysis.
• Amorphous biosolids present unique spectroscopic challenges due to mixed rigid/mobile domains and spectral complexity.

Purpose of the Study:

• To describe strategies for adapting solid-state NMR methods for structural determination of amorphous biosolids.
• To address challenges in NMR analysis of disordered materials, such as signal sampling and spectral complexity.
• To provide a holistic approach for analyzing macromolecular systems in amorphous biological samples.

Main Methods:

• Adaptation of various solid-state NMR techniques, including 1D, 2D, and 3D experiments.
• Utilizing hybrid experiments combining direct excitation and cross-polarization (CP) based methods.
• Employing heteronuclear (e.g., ¹³C-¹⁵N) spin coupling and multidimensional NMR to resolve spectral crowding and overlap.

Main Results:

• Demonstrated strategies for obtaining molecular structures and compositions of amorphous biosolids.
• Showcased how hybrid NMR experiments provide a more comprehensive view of macromolecular systems.
• Illustrated the utility of spectral filtering, multidimensional NMR, and spin coupling for detailed structural analysis.

Conclusions:

• Solid-state NMR techniques can be effectively adapted to overcome challenges in studying amorphous biological materials.
• Hybrid and multidimensional NMR approaches offer powerful tools for structural elucidation of disordered biosystems.
• These methods enable detailed molecular insights into complex, non-crystalline biological matter, advancing functional understanding.