Virus particle assembly into crystalline domains enabled by the coffee ring effect

Area of Science:

• Biophysics
• Materials Science
• Nanotechnology

Background:

• Tobacco mosaic virus (TMV) is a rod-like virus with potential applications in nanotechnology.
• Understanding self-assembly processes is crucial for designing novel nanomaterials.
• Evaporation-driven self-assembly in colloidal systems is a well-studied phenomenon.

Purpose of the Study:

• To investigate the rapid assembly of tobacco mosaic virus particles into 3D domains.
• To characterize the structure and orientation of virus particles within these domains.
• To explore the feasibility of using X-ray microdiffraction for analyzing these assembled structures.

Main Methods:

• Utilizing capillary flow-driven alignment at the contact line of evaporating droplets.
• Employing atomic force microscopy (AFM) to resolve individual virus particles.
• Applying X-ray microdiffraction, including Grazing-Incidence Small-Angle X-ray Scattering (GISAXS), to probe crystalline domains.

Main Results:

• TMV particles rapidly assemble into 3D crystalline domains driven by capillary flow during droplet evaporation.
• AFM confirmed the presence of ∼150 Å diameter virus particles within domains at the coffee-ring residue.
• X-ray microdiffraction and GISAXS revealed that rod-like virus particles are oriented parallel to the rim and allowed calculation of a low-resolution electron density projection.

Conclusions:

• Capillary flow during droplet evaporation is an effective method for rapid, ordered self-assembly of TMV particles into crystalline domains.
• The oriented crystalline structures can be characterized by AFM and X-ray microdiffraction.
• GISAXS geometry is suitable for collecting reflection intensities to determine low-resolution structural information along the virus axis.