A secondary structure within small peptides guiding spontaneous self-aggregation and nanoparticle formation

Area of Science:

• Biochemistry
• Structural Biology
• Materials Science

Background:

• Polyhedrin from Autographa californica baculovirus forms protective crystals (polyhedra) for baculovirus.
• These viral crystals maintain infectivity for years at room temperature.
• Understanding polyhedrin's self-aggregation is key to its protective function.

Purpose of the Study:

• To identify the smallest fragment of polyhedrin responsible for self-aggregation.
• To investigate the role of secondary structures in spontaneous nanoparticle formation.
• To explore the potential of these self-aggregating peptides for novel applications.

Main Methods:

• Investigated fragments of Autographa californica baculovirus polyhedrin.
• Synthesized peptides with varying sequences but similar secondary structures (beta-sheet, alpha-helix).
• Characterized the self-aggregation properties and resulting nanoparticle formation.

Main Results:

• A 29-amino acid polyhedrin fragment was identified as the smallest self-aggregating unit.
• This fragment contains a beta-sheet followed by an alpha-helix.
• Synthesized peptides with similar secondary structures also formed nanoparticles of diverse sizes and geometries.
• Individual beta-sheet and alpha-helix structures also demonstrated aggregation capabilities.
• Self-aggregating peptides retained this property even when fused to green fluorescent protein.

Conclusions:

• Specific secondary structures (beta-sheets and alpha-helices) are sufficient for spontaneous nanoparticle formation.
• This self-assembly property is inherent to these structures, independent of the full polyhedrin protein.
• The findings open avenues for designing novel self-assembling nanomaterials.