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

Tobacco mosaic virus particles can be rapidly assembled into 3D-domains by capillary flow-driven alignment at the triple contact-line of an evaporating droplet. Virus particles of ∼150 Å diameter can be resolved within individual domains at the outer rim of the "coffee-ring" type residue by atomic force microscopy. The crystalline domains can also be probed by X-ray microdiffraction techniques. Both techniques reveal that the rod-like virus particles are oriented parallel to the rim. We further demonstrate the feasibility of collection of hk0 reflection intensities in GISAXS geometry and show it allows calculating a low-resolution electron density projection along the rod axis.