Comparative Study of Non-Enveloped Icosahedral Viruses Size

Area of Science:

• Virology
• Biophysics
• Nanotechnology

Background:

• Transmission electron microscopy (TEM) is standard for determining virion size, but sample preparation can alter morphology.
• Dynamic light scattering (DLS) and nanoparticle tracking analysis (NTA) measure virion size in liquid, closer to native conditions.
• NTA offers higher resolution and is less sensitive to impurities than DLS.

Purpose of the Study:

• To compare virion size measurements obtained by TEM, DLS, and NTA for various non-enveloped icosahedral viruses.
• To evaluate the contribution of the electrical double layer (EDL) to hydrodynamic diameter measurements.
• To assess the agreement between TEM, DLS, and NTA results, particularly after accounting for EDL effects.

Main Methods:

• Analysis of encephalomyocarditis virus (animal), and cauliflower mosaic virus, brome mosaic virus, and bean mild mosaic virus (plant) using TEM, DLS, and NTA.
• Freshly purified virus samples were used for all techniques.
• Evaluation of the electrical double layer (EDL) contribution to hydrodynamic diameter.

Main Results:

• TEM consistently yielded smaller virion sizes compared to DLS and NTA.
• Hydrodynamic diameter data from DLS for bean mild mosaic virus and from NTA for all viruses were obtained for the first time.
• Adjusting DLS and NTA data for EDL thickness resulted in better agreement with TEM measurements.

Conclusions:

• TEM size measurements may underestimate virion dimensions due to sample preparation artifacts.
• DLS and NTA are valuable complementary techniques for assessing virion size and aggregation in solution.
• Accounting for the electrical double layer is crucial for reconciling size measurements between dry (TEM) and solution-based (DLS, NTA) methods.