Because of Small Flitters

Large particles sometimes diffuse faster than thought

small flitters
Long virus in a lamellar phase, which is formed by short viruses. The diffusion rate can be determined by means of fluorescent tracer particles (red = long, green = short). Copyright: Research Center Jülich / Pavlik Lettinga

The smaller the object, the brighter it dissipates in its surroundings. Think of fine sand grains and coarse gravel stones in the river or crumbs and bread on the kitchen table. The same behavior is also shown by microscopically small particles, which are distributed over time in the space, stimulated by the surrounding molecules. As early as 1905, Albert Einstein was able to provide the theoretical proof that the velocity of this so-called Brownian motion is inversely proportional to the radius of a particle, ie its magnitude.Researchers from the Research Center Jülich, the KU Leuven and the Research Center CRPP in Bordeaux have now found an exception to this rule. In their experiments, they used a lamellar system in which the large particles are more mobile than the small ones.

The researchers used tailor-made viruses for their work: many short and a few long viruses, whose movement can be traced well under the fluorescence microscope. At high concentrations, the short rods become a crystal structure in parallel layers. Measurements showed that the force of the short rods in layers is much weaker on the longer rods. These have more space and move faster than the shorter viruses.

The astonishing mobility is due to an effect that is known by many parking lots: oversized vehicles occasionally create more space by occupying several parking spaces. The same is true with the surviving viruses, which extend over several places in the existing layer structure. The findings may also be of practical use. They may lead to the development of rapidly diffusing molecules for possible applications in cell biology and drugs, the researchers estimate.

Original publication:

Fast Diffusion of Long Guest Rods in a Lamellar Phase of Short Host Particles
Laura Alvarez, M. Paul Lettinga, Eric Grelet
Phys. Rev. Lett. (Published 25 April 2017), DOI: 10.1103 / PhysRevLett.118.178002