COVID-19 does not need to be introduced. Last year, the disease, which is caused by the SARS-CoV-2 virus, reached every continent in the world. At the end of March 2021, an estimated 128 million cases were recorded, of which nearly three million were fatal. As scientists race to develop vaccines and politicians coordinate their distribution, basic research into what makes this virus successful is also underway.
Within the Mathematics, Mechanics and Materials Unit of the Okinawa Institute of Science and Technology Graduate University (OIST), postdoctoral researcher Dr Vikash Chaurasia and Professor Eliot Fried used energy minimization techniques to examine proteins loaded on biological particles. Previously they were looking for cholesterol molecules, but when the pandemic hit they realized that with the methods they had developed they could be applied to the new virus. They collaborated with researchers Mona Kanso and Professor Jeffrey Giacomin, from Queen’s University in Canada, to take a close look at SARS-CoV-2 and see how the “ spikes ” of the virus (officially called peplomers) shape. contributes to its success. to spread so prolifically. Their study was recently published in Fluid physics.
“When considering a single coronavirus particle, it is common to think of a sphere with many spikes or smaller spheres distributed over its surface,” Dr Chaurasia said. “This is how the virus was originally modeled. But this model is a rough draft and over the last year we have come to learn a lot more about what the virus looks like.”
Instead, Dr Chaurasia pointed out, the “ tips ” of the coronavirus particle are actually shaped like three small spheres stacked together to form a triangular shape. This is an important consideration because the shape of a viral particle can influence its ability to disperse.
To understand this, imagine a ball moving through space. The ball will follow a curve, but in doing so, it will also spin. The speed at which the ball spins is called its rotational diffusivity. A SARS-CoV-2 particle moves in the same way as this bullet although it is suspended in a liquid (specifically, tiny droplets of saliva). The rotational diffusivity of the particle impacts its ability to align and attach to objects (such as a person’s tissues or cells) and this has been critical in its ability to propagate so rapidly d ‘one person to another. Higher rotational diffusivity will mean the particle will shake and tremble as it follows a path – and therefore may have difficulty attaching to objects or effectively bouncing off an object to continue moving through air. Whereas a lower rotational diffusivity has the opposite effect.
Another consideration was the load of each peak. The researchers assumed that each was equally charged. The same charges always repel each other, so if there are only two points on a particle and they have equal charges, they will be located at either pole (as far away as possible from the each other). As more equal load spikes are added, they become evenly distributed over the surface of the sphere. This provided the researchers with a geometric arrangement from which they were able to calculate rotational diffusivity.
Previously, the researchers examined a virus particle with 74 spikes. For this new study, they used the same particle, but replaced the single-bead tips for the three-bead triangles. When they did this, the rotational diffusivity of the particle was found to decrease by 39%. Additionally, this trend was found to continue with the addition of additional peaks.
This was an important finding – having a lower rotational diffusivity means that viral particles can better align and attach to objects and people. Thus, this study suggests that the triangular shaped spikes contributed to the success of SARS-CoV-2.
“We know it’s more complicated than that,” explained Dr Chaurasia. “The tips might not be equally charged. Or they might be flexible and able to twist. Also, the particle’s ‘body’ might not be a sphere. So we plan to do more research in this area. “
Another interesting feature of this research is its connection to a question asked over a century ago by physicist JJ Thomson, who explored how a defined number of charges will be distributed over a sphere.
“I find it fascinating that a problem that was envisioned over 100 years ago has such relevance to the situation we find ourselves in today,” said Professor Eliot Fried. “Although this question was first asked from the angle of curiosity and intellectual interest, it turned out to be applicable in unexpected ways. This shows why we must not lose sight of the importance of basic research.
Scientists at OIST and Queen’s University intend to continue collaborating on this type of research to shed light on the success of SARS-CoV-2. Queen’s University researchers have just received a Mitacs Globalink Fellowship to enable lead author Mona Kanso to travel between Canada and Japan and work more closely with OIST.