DNA mutations can have severe health consequences around the world, including birth defects and cancer, but they’re caused by a complex web of factors. Now, in an innovative, interdisciplinary study, a group of quantum biologists have applied theoretical physics modelling to DNA replication to uncover some of the mechanisms at play at an atomic level.
Ok, what’s quantum biology?
Quantum physics is the nature and behaviour of matter and energy at atomic and subatomic levels, often explained by quantum theory. Quantum biology is an emerging multidisciplinary field of science, that brings together nuclear physicists, biochemists and molecular biologists, to explore how quantum mechanics plays a role in living cells.
Using state-of-the-art computer simulations and quantum mechanics, a team from Surrey’s Leverhulme Quantum Biology Doctoral Training Centre (LQBDTC) explored how proton tunnelling might be linked to DNA mutations. This research paper has been published in Physical Chemistry Chemical Physics.
And what’s proton tunnelling?
Proton tunnelling is the instantaneous disappearance of a proton from one site, and the appearance of the same proton at a nearby site, across a barrier. Protons are 2000 times larger than an electron, so have a much lower probability of occurring, especially if the width of the potential barrier is decreased. Proton tunnelling is associated with hydrogen bonds, where a hydrogen atom without its electron is reduced to being a proton, which gives it potential to cross this boundary, aka tunnel.
What’s it got to do with DNA?
Our DNA (Deoxyribonucleic acid) is made up of two strands of complementary bases, adenine-thymine (A-T) and guanine-cytosine (G-C), that are held together by Hydrogen bonds. Hydrogen bonds are not a chemical bond, but rather an electrostatic force that can be easily disrupted. In certain conditions, through proton tunnelling, the hydrogen atoms can exist in multiple locations simultaneously, spreading out like waves. This can lead to atoms being on the wrong strand of DNA, which can lead to a tautomer, aka a mutation only occurring on that strand. DNA replicates with a spontaneous mutation occurring once every 108–1011 bases replicated. It sounds like a rare occurrence, but the DNA in each human cell is around three billion nucleotides long, and is replicated about two trillion times each day, which means it occurs roughly twenty times per day. Having a better understanding of this process offers the potential to decrease the likelihood of mutations occurring, and thus a decrease in its severe health consequences.
“Many have long suspected that the quantum world – which is weird, counter-intuitive and wonderful – plays a role in life as we know it,” says Dr Marco Sacchi, project leader and Royal Society Research Fellow at the University of Surrey. “While the idea that something can be present in two places at the same time might be absurd to many of us, this happens all the time in the quantum world, and our study confirms that quantum tunnelling also happens in DNA at room temperature.”
But what does it all mean?
According to one of the co-authors of the study, Louie Slocombe, a PhD student at the LQBDTC: “there is still a long and exciting road ahead of us to understand how biological processes work on the subatomic level, but our study – and countless others over the recent years – have confirmed quantum mechanics are at play. In the future, we are hoping to investigate how tautomers produced by quantum tunnelling can propagate and generate genetic mutations.”