Stepwise reversible nanomechanical buckling in a viral capsid

Area of Science:

• Virology
• Nanomechanics
• Biophysics

Background:

• Viruses are nanoscale infectious agents with protein capsids protecting genomic material.
• Atomic force microscopy (AFM) nanoindentation has revealed insights into viral elastic properties and stability.
• The dynamic behavior of viral capsids remains largely unexplored.

Purpose of the Study:

• To investigate the mechanical dynamics of mature T7 bacteriophage capsids using high-resolution nanoindentation.
• To understand the role of capsid structure and protein dynamics in viral stability.

Main Methods:

• High-resolution nanoindentation experiments on mature, DNA-filled T7 bacteriophage particles.
• Dynamic force spectroscopy to analyze thermally activated processes.

Main Results:

• Nanoindentation force traces showed discrete, reversible, stepwise transitions (∼0.6 nm increments) causing capsid buckling.
• These transitions persisted after DNA removal, indicating they originate from the protein capsid.
• Capsid consolidation against force is a rapid, thermally activated process, significantly faster than spontaneous buckling.

Conclusions:

• T7 bacteriophage capsid stability is under strong dynamic control, governed by the proteinaceous structure.
• The observed nanomechanical properties suggest a mechanism for protecting viral genomic material.
• The nanomechanics approach can be applied to study other viruses and nanoscale containers.