Structure, morphology, and assembly behavior of kafirin

Area of Science:

• Biomaterials Science
• Protein Chemistry
• Materials Science

Background:

• Prolamins, like kafirin from sorghum, are gaining attention as sustainable, biodegradable, and cost-effective biomaterials.
• However, a comprehensive understanding of kafirin's composition, structure, and self-assembly is lacking.

Purpose of the Study:

• To characterize the composition, structure, and self-assembly behavior of kafirin extracted from sorghum.
• To investigate the influence of solvent polarity and protein concentration on kafirin's conformational changes and assembly.

Main Methods:

• Kafirin extraction and compositional analysis.
• Spectroscopic techniques (e.g., circular dichroism) to determine secondary structure.
• Small-angle X-ray scattering (SAXS) to analyze molecular conformation.
• Atomic force microscopy (AFM) to visualize morphology of kafirin assemblies.

Main Results:

• Kafirin composition was determined, with α-kafirin as the major fraction (~68%).
• Solid-state kafirin exhibited significant α-helix content (~49%), which increased with decreasing solvent polarity.
• SAXS revealed stretched conformations in solution, with dimensions varying based on solvent (tert-butanol, isopropanol, ethanol).
• AFM showed uniform particle morphology at low concentrations and disk-like/rod-like structures at high concentrations due to solvent evaporation-induced interactions.

Conclusions:

• Kafirin's secondary structure and conformation are sensitive to solvent polarity.
• Protein concentration and solvent polarity are key factors in regulating kafirin assembly morphology.
• These findings offer a method for tuning prolamin-based biomaterial fibrillation.