Could quantum mechanics—a field Albert Einstein once ridiculed as “spooky”—affect us in a most personal way? Possibly. Theoretical research is beginning to suggest that quantum effects could drive mutations in human DNA. If true, it could change our understanding of cancer, genetic diseases, and even the origins of life.
Scientists once thought biological systems were too warm, wet, and chaotic to experience strange quantum effects like proton tunneling, where the particle’s waveform expands, allowing it to cross an energy barrier that would normally block its passage. In general, the more heat and chaos around, the less quantum effect there is. Therefore, for many years scientists thought that the quantum behavior in the human body was too small to matter.
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But you can’t find what you’re not looking for. As quantum physicists begin to poke around in the chaotic and complex world of biology, even within our DNA, they find quantum mechanics at play. Welcome to the world of quantum biology.
An introduction to point mutations
The iconic double helix of DNA consists of two twisting strands of molecules with bits in the middle that connect like puzzle pieces, each of which has one of four different shapes named with a letter. T-forms combine with A-forms and G-forms combine with C-forms, forming what is known as “base pairs”. These small molecular branches connect through weak attractive forces between their hydrogen atoms, which have a single proton and electron.
Sometimes an error occurs and the letters are paired incorrectly – an error we call point mutation. Point mutations can add up and cause problems with DNA, sometimes leading to cancer or other health problems. Mostly the result of errors during DNA replication, point mutations can also be caused by X-rays, UV radiation, or anything that stimulates atomic particles to move out of their ordered places.
For 50 years, researchers have debated whether protons switching positions between weakly bound DNA strands could cause point mutations. The answer seemed to be no. Many studies concluded that the intermediate base-pair states created by proton switching were too unstable and short-lived to be replicated in DNA. But a new study published in the journal communication physics notes that these states can be common and stable, and that quantum processes can drive their formation.
Researchers modeled proton transfer between G:C base-pair hydrogen bonds in an infinite sea of feather-like vibrating particles that represent the chaotic cellular environment. Their calculations show that proton transfer through quantum tunneling for G:C junctions in the center of a DNA helix can occur very quickly – within a few hundred femtoseconds, or 0.000000000000001 seconds. Such a rate is much faster than our biological time scale.
This switching happens so quickly and so often that it ‘appears’ to our DNA as if some of the protons are always visiting their neighbors, just as an image on a screen can flash so quickly that it appears still to our eyes. This super-fast swapping of protons from one side of the bridge to the other means that base pairs are constantly switching between their original shape and a slightly altered shape. These intermediate forms can cause mismatches during DNA replication as strands are opened, read, and copied.
Instead of preventing protons from tunneling, our biological heat can act as a source of thermal activation, giving the protons enough energy to jump to the other side. In fact, proton transfer by quantum tunneling is four times more likely than predicted by classical physics. These occurrences are not only frequent, but also long-lasting. Based on previous computational studies, the researchers predict that these molecular changes should be stable long enough to be replicated – causing a mutation.
There are two main limitations at work. First, the researchers did not examine A:T base pairs and found that the intermediate state for these bonds is very unstable and unlikely 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 consolation?
Based on the team’s calculations, point mutations should be much more common in our DNA than they are. The researchers attribute this difference to “highly efficient DNA repair mechanisms” that find the damage and reverse it. For example, our DNA replication machinery includes a “proofreading” capability where mistakes are detected and corrected – much like a typo. Thank goodness for biological editors.
The ease of proton tunneling and the longevity of these intermediate states may even be relevant to studies of the origin of life, the researchers write, since the rate of early evolution is linked to the mutation rate of single-stranded RNA. Although the quantum world may seem strange and far away, it may have played a role in giving us life – and taking it from us.