In light of our current situation, I’m sure you’ve heard of UV light and it being used to disinfect surfaces. If you have not heard, I’ll fill you in – certain wavelengths of ultraviolet light can disrupt a bacteria or viruses’ DNA and ultimately stops it from replicating and spreading further. The specific wavelength that can do this is UV-C, which has the shortest wavelength (200 – 280 nm) and highest frequency of all other types of UV. But amongst all this buzz, have you found yourself wondering exactly how UVC light kills bacteria and viruses? Then you have come to the right place!
How exactly does UV-C light kill germs?
Electrons are subatomic particles that are responsible for bonding in molecules, and these electrons sit in defined energy levels called orbitals. We can use light to excite (increase the energy of) electrons into higher energy orbitals – UVC light is of the wavelength that is capable of exciting electrons in DNA and RNA. When the electrons are excited, they cause molecules to change, which are then ready to react and make new products.
When UVC light is shone on DNA or RNA, the UVC photons excite electrons and cause certain DNA and RNA bases (Thymine and Uracil) to form intra strand crosslinks (as seen in the diagram above) so rather than the bases bonding with their corresponding bases, they form a link with another base or even another DNA strand. This reaction forms pyrimidine dimers and permanently alters the structure of DNA and RNA. Uracil is a base in RNA, and RNA is responsible for cell replication and protein synthesis, both of which are processes needed for the survival of an organism. Hence, killing the cell or rendering it inactive.
As seen in the diagram above, Uracil and Thymine both have an absorption maximum at the wavelengths between 250-280nm, which is the wavelength range of UVC. A high absorption means more DNA/RNA damage.
And the germicidal effectiveness of UV light in this E. coli sample is 260-265nm, meaning that UVC light is a very effective killer for this E. coli sample!
This sterilising prowess of UVC is true for coronaviruses too (SARS-CoV, MERS-CoV and HCoV), recent studies show that UV-C light can change the structure of Coronaviruses. (Click here to read the full article)
These contact plates have Sars-Cov-2 on them and you can see a high level of inactivation after just 1 second (87.4%) of irradiation and after 60 seconds the strain of Sars-Cov-2 has been effectively deactivated.
To sum it all up, UVC light has a proven sterilising power to organisms and is shown to be able to kill 99.9% of bacteria and virus including Coronaviruses. The possibilities for UVC light are limitless and it is looking to play a big role in bringing people back to work and public places in a safe way – so stay tuned for our blog as we continue giving you insightful information on UV and its role in our future.
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