COVID-19 and the search for a vaccine

As the UK’s vaccination programme hits the headlines, Ronnie Cohen takes a look at the microscopic elements that are affected by viruses and the vaccines developed to fight them.

First, we should consider the size of the coronavirus, which is microscopic in size. The Coronavirus (SARS-CoV-2, COVID) is a virus that is 120 nanometres (billionths of a metre) across.

Human red blood cells typically have a diameter of 6-8 micrometres (millionths of a metre) across, are 2-2.5 micrometres at their thickest point and 0.8-1 micrometres at the thinnest point. Human white blood cells are 12-17 micrometres in diameter. Most bacteria are 0.2-10 micrometres in diameter. On average, bacteria contain approximately 2 million proteins per cell. Dimensions of DNA are measured in nanometres. The size of an antibody molecule is about 10 nanometres across. Antibodies are used by the immune system to fight pathogens and viruses. A vaccine for COVID-19 helps the immune system to recognise the threat of COVID-19 to fight off the disease.

Understanding the coronavirus and its effects on humans involves research into its effects on various microscopic properties. These properties are measured in metric units because the metric system has been designed to measure the smallest and largest elements in the universe which are beyond the scope of the imperial system. The metric system is far superior to the imperial system at both ends of the scale in this respect. This research is essential in the development of vaccines, which involves many different measurements (e.g. quantities of ingredients, cell sizes, blood samples, etc.). As this article has illustrated, some of these measurements are extremely small.

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2 thoughts on “COVID-19 and the search for a vaccine”

  1. For the benefit of those who are unfamniliar with these small measurements,
    1000 nanometres (nm) = 1 micrometre (μm)
    1000 micrometres (μm) = 1 millimetre (mm)
    1000 millimetres (mm) – 1 metre (m).
    A sheet of standard computer paper is 120 μm in thickness. Thsi can be verified by measuring the thickness of a pack of 500 sheets of paper (60 mm). I think that this puts the other measurements quoted in the article into perspective. It might be useful to compare these biological structures with atomic structures. Possibly the best example is that salt (NaCl) crystals are composed of sodium and chlorine atoms in a lattice spaced 0.56 nm apart.
    One of the biggest problems in trying to view these things through a microscope is that the wavelength of visible light is in the range 400-700 nm, which means that we cannot see anything smaller than twice this size using visible light (ie of the order of 1 μm), no matter how good our microscope is. Thwe way around this is to use an electron microscope.

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  2. I think that was a very helpful addition to the original article on the sizes of bacteria and viruses. I think it’s worth adding that an electron microscope works on the principle of the duality between particles (electrons) and waves, so it is possible to achieve a short enough wavelength for viewing an object by giving the electrons high enough energy. The problem is that high energy electrons can cook the sample! So in practice electron microscopes have only a limited range of application. Consequently much of the detailed structure on the molecular scale has been determined by indirect methods of observation and measurement. Such methods were extensively used to find the molecular structure of DNA in the 1950s.

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