Quantum mechanics could explain why DNA can spontaneously mutate
Date:
May 5, 2022
Source:
University of Surrey
Summary:
The molecules of life, DNA, replicate with astounding precision,
yet this process is not immune to mistakes and can lead to
mutations. Using sophisticated computer modelling, a team of
physicists and chemist have shown that such errors in copying can
arise due to the strange rules of the quantum world.
FULL STORY ==========================================================================
The molecules of life, DNA, replicate with astounding precision, yet
this process is not immune to mistakes and can lead to mutations. Using sophisticated computer modelling, a team of physicists and chemists
at the University of Surrey have shown that such errors in copying can
arise due to the strange rules of the quantum world.
==========================================================================
The two strands of the famous DNA double helix are linked together by
subatomic particles called protons -?the nuclei of atoms of hydrogen --
which provide the glue that bonds molecules called bases together. These so-called hydrogen bonds are like the rungs of a twisted ladder that
makes up the double helix structure discovered in 1952 by James Watson and Francis Crick based on the work of Rosalind Franklin and Maurice Wilkins.
Normally, these DNA bases (called A, C, T and G) follow strict rules
on how they bond together: A always bonds to T and C always to G. This
strict pairing is determined by the molecules' shape, fitting them
together like pieces in a jigsaw, but if the nature of the hydrogen bonds changes slightly, this can cause the pairing rule to break down, leading
to the wrong bases being linked and hence a mutation. Although predicted
by Crick and Watson, it is only now that sophisticated computational
modelling has been able to quantify the process accurately.
The team, part of Surrey's research programme in the exciting new field
of quantum biology, have shown that this modification in the bonds
between the DNA strands is far more prevalent than has hitherto been
thought. The protons can easily jump from their usual site on one side of
an energy barrier to land on the other side. If this happens just before
the two strands are unzipped in the first step of the copying process,
then the error can pass through the replication machinery in the cell,
leading to what is called a DNA mismatch and, potentially, a mutation.
In a paper published this week in the journal Nature Communications
Physics, the Surrey team based in the Leverhulme Quantum Biology Doctoral Training Centre used an approach called open quantum systems to determine
the physical mechanisms that might cause the protons to jump across
between the DNA strands.
But, most intriguingly, it is thanks to a well-known yet almost magical
quantum mechanism called tunnelling -- akin to a phantom passing through
a solid wall - - that they manage to get across.
It had previously been thought that such quantum behaviour could not
occur inside a living cell's warm, wet and complex environment. However,
the Austrian physicist Erwin Schro"dinger had suggested in his 1944 book
What is Life? that quantum mechanics can play a role in living systems
since they behave rather differently from inanimate matter. This latest
work seems to confirm Schro"dinger's theory.
==========================================================================
In their study, the authors determine that the local cellular environment causes the protons, which behave like spread out waves, to be thermally activated and encouraged through the energy barrier. In fact, the
protons are found to be continuously and very rapidly tunnelling back
and forth between the two strands. Then, when the DNA is cleaved into
its separate strands, some of the protons are caught on the wrong side,
leading to an error.
Dr Louie Slocombe, who performed these calculations during his
PhD, explains that: " The protons in the DNA can tunnel along the
hydrogen bonds in DNA and modify the bases which encode the genetic information. The modified bases are called "tautomers" and can survive the
DNA cleavage and replication processes, causing "transcription errors"
or mutations." Dr Slocombe's work at the Surrey's Leverhulme Quantum
Biology Doctoral Training Centre was supervised by Prof Jim Al-Khalili (Physics, Surrey) and Dr Marco Sacchi (Chemistry, Surrey) and published
in Communications Physics.
Prof Al-Khalili comments: "Watson and Crick speculated about the
existence and importance of quantum mechanical effects in DNA well
over 50 years ago, however, the mechanism has been largely overlooked."
Dr Sacchi continues: "Biologists would typically expect tunnelling to
play a significant role only at low temperatures and in relatively simple systems. Therefore, they tended to discount quantum effects in DNA. With
our study, we believe we have proved that these assumptions do not hold."
========================================================================== Story Source: Materials provided by University_of_Surrey. Note: Content
may be edited for style and length.
========================================================================== Journal Reference:
1. Louie Slocombe, Marco Sacchi, Jim Al-Khalili. An open quantum
systems
approach to proton tunnelling in DNA. Communications Physics,
2022; 5 (1) DOI: 10.1038/s42005-022-00881-8 ==========================================================================
Link to news story:
https://www.sciencedaily.com/releases/2022/05/220505085605.htm
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