Could quantum mechanics – a field that Albert Einstein once called “spooky” – affect us in a very personal way? Very probably. Theoretical research is beginning to suggest that quantum effects could drive mutations in human DNA. If true, it could change the way we understand cancer, genetic diseases, and even the origins of life.
Scientists once thought that biological systems were too hot, humid and chaotic to experience strange quantum effects like the proton tunnel effect, in which the particle’s waveform propagates, allowing it to cross an energetic barrier. which would normally block its passage. Generally, the more heat and chaos around, the weaker the quantum effect; thus, for many years, scientists thought that in the human body, quantum behaviors would be too small to matter.
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But you can’t find what you’re not looking for. As quantum physicists begin to delve into the messy and complex world of biology, they discover that quantum mechanics is at play, even in our DNA. Welcome to the world of quantum biology.
An introduction to point mutations
DNA’s iconic double helix is formed from two coiled molecular strands with pieces in the center that connect like puzzle pieces, each with one of four different letter-named shapes. T-forms bind to A-forms and G-forms connect to C-forms, forming what are known as “base pairs”. These small molecular branches connect by weak attractions between their hydrogen atoms, which have a single proton and a single electron.
Sometimes an error occurs and the letters are not paired correctly – an error we call a point mutation. Point mutations can add up and cause DNA problems, sometimes leading to cancer or other health problems. Most often the result of errors during DNA replication, point mutations can also be caused by exposure to X-rays, UV rays, or anything that excites atomic particles to move from their ordered places. .
For 50 years, researchers debated whether protons changing position between loosely bound DNA strands could cause point mutations. The answer seemed no. Many studies have concluded that the base pair intermediate states created by proton switching are too unstable and short-lived to be replicated in DNA. But a new study published in the journal Physics of communications finds that these states can be frequent and stable, and that quantum processes can lead to their formation.
The researchers modeled the transfer of protons between the hydrogen bonds of the G:C base pair in an endless sea of vibrating spring-like particles, representing the chaotic cellular environment. Their calculations show that quantum tunneling proton transfer can occur very quickly for G:C connections at the center of a DNA helix – within a few hundred femtoseconds, or 0.000000000000001 seconds. Such a rhythm is much faster than our biological time scale.
This switching occurs so quickly and so often that to our DNA it “appears” as a proportion of protons always visiting their neighbors, in the same way that an image on a screen may flash so rapidly that it appears motionless to our eyes. This lightning-fast switching of protons from one side of the bridge to the other means that the base pairs are constantly changing between their original shape and a slightly different shape. These intermediate forms can cause a lag during DNA replication, when strands are opened, read and copied.
Instead of stopping the protons from tunneling, our biological heat can act as a source of thermal activation, giving the protons enough energy to get through to the other side. Indeed, proton transfer by quantum tunneling is four times more likely than predicted by classical physics. Not only are these events common, but they also last for a long time. Based on previous computational studies, the researchers predict that these molecular changes should be stable long enough to replicate, causing a mutation.
There are two main limitations with the job. First, the researchers did not study A:T base pairs, noting that for these bonds, the intermediate state is highly unstable and less likely to play a role in DNA mutations. Second, this theoretical work would benefit from experimental testing to validate or challenge the results.
A quantum of comfort?
According to the team’s calculations, point mutations should appear in our DNA much more frequently than they do. The researchers attribute this difference to “highly efficient DNA repair mechanisms” that detect and repair damage. For example, our DNA replication machinery includes a “proofreading” capability, in which errors are detected and corrected – much like a typo. Thank goodness for organic copy editors.
The ease of proton tunneling and the longevity of these intermediate states could even be relevant to origin-of-life studies, the researchers write, because the rate of early evolution is related to the mutation rate of the single-stranded RNA. So while the quantum world may seem strange and distant, it may have played a role in giving us life – and also taking it away.