The influence of quantum tunnelling on double hydrogen transfers within DNA base pairs is investigated by solving the time-dependent Schrodinger equation (TDSE) for a one-dimensional double well potential, whilst accounting for environment coupling. The energies of the canonical (standard, amino-keto) and tautomeric (non-standard, imino-enol) charge-neutral forms of the adenine-thymine base pair (A-T and A*-T*, respectively) are calculated using density functional theory. These compare favourably to results in existing literature. The reaction pathway is also calculated using a transition state search to provide the barrier height and shape, and these are combined to create the potential using a polynomial fit. It is found that tunnelling is very unlikely to be a significant mechanism for the creation of adenine-thymine tautomers within DNA, with the anti-Zeno effect from environment coupling only being able to boost the tunnelling probability at any given time to ~2 x 10-9. This is barely increased when varying several parameters, such as barrier height, potential asymmetry, and mass (kinetic isotope effect). In addition, the general effect on a quantum system by its surrounding environment is explored. A novel comparison between two distinct methods of environment coupling - dissipation (via the addition of a Lindblad term to the master equation) and von Neumann measurements - is performed. This is done using a simpler model of benzoic acid dimer, where it is shown that the two methods describe the same physical process of decoherence and can be thought of as equivalent until the link between them breaks down at high temperatures and measurement frequencies.
The influence of quantum tunnelling on double hydrogen transfers within DNA base pairs is investigated by solving the time-dependent Schrodinger equation (TDSE) for a one-dimensional double well potential, whilst accounting for environment coupling. The energies of the canonical (standard, amino-keto) and tautomeric (non-standard, imino-enol) charge-neutral forms of the adenine-thymine base pair (A-T and A*-T*, respectively) are calculated using density functional theory. These compare favourably to results in existing literature. The reaction pathway is also calculated using a transition state search to provide the barrier height and shape, and these are combined to create the potential using a polynomial fit. It is found that tunnelling is very unlikely to be a significant mechanism for the creation of adenine-thymine tautomers within DNA, with the anti-Zeno effect from environment coupling only being able to boost the tunnelling probability at any given time to ~2 x 10-9. This is barely increased when varying several parameters, such as barrier height, potential asymmetry, and mass (kinetic isotope effect). In addition, the general effect on a quantum system by its surrounding environment is explored. A novel comparison between two distinct methods of environment coupling - dissipation (via the addition of a Lindblad term to the master equation) and von Neumann measurements - is performed. This is done using a simpler model of benzoic acid dimer, where it is shown that the two methods describe the same physical process of decoherence and can be thought of as equivalent until the link between them breaks down at high temperatures and measurement frequencies.
• Published in Nature's sister journal Communications Physics, proposing an 'open quantum systems approach to proton tunnelling in DNA'. • Analysis of G-C base pairs confirmed that the proton transfer rate by tunnelling is overwhelmingly higher than classical methods even at biological temperatures and in a dissipative environment. • Demonstrated a high tautomeric occupation probability... suggesting that DNA mutation is deeply governed by quantum mechanical processes. [Quantum Biology Society] Research revealing that the fundamental cause of mutations threatening the genetic stability of DNA—the core of life preservation—is based on quantum mechanical phenomena rather than classical biochemical reactions is drawing significant attention from the academic community. A paper published in Communications Physics, a sister journal of Nature, titled "An open quantum systems approach to proton tunnelling in DNA" verified this innovative hypothesis with a sophisticated physical model. A joint research team, including Louie Slocombe and Professor Jim Al-Khalili, thoroughly analyzed the quantum mechanical processes related to proton transfer. ■ Protons Piercing Through Hydrogen Bonds, Inducing 'Point Mutations' If a proton moves out of its orbit within the hydrogen bonds of the Guanine-Cytosine (G-C) base pair connecting the DNA double helix structure, tautomerisation occurs, altering the chemical structure of the base, which can lead to a point mutation, an error in genetic information. However, exactly how this process occurs in a warm and complex biological environment has long been a matter of debate. To solve this challenge, the research team applied an open quantum system that integrated an accurate structural model of the G-C base pair with the quantum dynamics of the hydrogen bond proton and the influence of the decoherent and dissipative cellular environment. ■ Quantum Effects Surviving Even in Biological Environments... "Tens of Thousands of Times Faster Than Over-the-Barrier Hopping" The analysis results completely overturned the conventional wisdom that quantum phenomena are confined only to the microscopic world or cryogenic temperatures. The research team found that, despite biological temperatures and environmental factors, the quantum tunnelling contribution to the proton transfer rate is several orders of magnitude (tens of thousands of times) larger than the classical 'over-the-barrier hopping' method, where particles gain energy to cross the barrier. Due to the strong quantum tunnelling effect, the canonical and tautomeric forms of the G-C base pair inter-convert over timescales far shorter than biological ones and very rapidly reach thermal equilibrium. ■ The Origins of Cancer and Evolution Lie in Quantum Probabilities What is even more surprising is that the tautomeric occupation probability through tunnelling reaches a significant level of 1.73 × 10⁻⁴. This suggests that such proton transfer may well play a far more dominant and important role in DNA mutation than the academic community has hitherto thought. This study, which proves that DNA mutations—the macroscopic consequences driving the onset of genetic diseases or cancer, and further, the evolution of life—are in fact thoroughly governed by microscopic quantum tunnelling phenomena, will serve as a powerful indicator of how Quantum Biology can innovate the paradigms of medicine and genetics in the future.
• A study published in the international journal Communications Physics demonstrated the phenomenon of proton tunneling inside DNA utilizing an open quantum systems approach. • The research confirmed that protons within DNA hydrogen bonds pass through binding barriers via quantum tunnelling, going well beyond simple thermal fluctuations, and that this plays a dominant role in the conversion of base pairs into rare tautomers. • This is a groundbreaking result proving that the fundamental genetic mutation process of life is driven by microscopic quantum tunneling probabilities, revealing that tautomeric states can induce natural point mutations. [Quantum Biology Society] The DNA double helix, which contains all the genetic information of living organisms, is stably maintained by hydrogen bonds between base pairs. However, even in this robust structure, unexplained point mutations occasionally occur, becoming the seeds of evolution and disease. Recently, a study demonstrating that quantum tunnelling—a bizarre physical law of the subatomic world—is deeply involved behind this fundamental biological phenomenon was published, surprising both the biology and physics communities. The paper detailing this groundbreaking discovery, titled "An open quantum systems approach to proton tunnelling in DNA," was made freely available in Communications Physics, a sister journal to the world-renowned Nature. A research team consisting of Louie Slocombe, Marco Sacchi, and Jim Al-Khalili from the University of Surrey in the UK led this interdisciplinary study. ■ The Power of Quantum Tunneling Beyond Classical Chemistry From the perspective of general classical biochemistry, it has been assumed that for protons forming DNA hydrogen bonds to change positions, sufficient thermal fluctuation is required to overcome the binding barrier. However, the researchers discovered a surprising fact through an open quantum systems model that precisely reflects the effects of decoherence and dissipation within the cellular environment. Protons instantly change their binding positions through quantum tunneling, passing through the barrier despite a lack of energy, and the contribution of quantum tunneling to the chemical reaction rate is several orders of magnitude larger than classical over-the-barrier hopping. ■ The Beginning of Mutation: Tautomeric Conversion According to the analysis, this quantum tunneling plays a dominant role in the conversion of Guanine-Cytosine (G-C) base pairs from their canonical form into highly rare and unstable tautomeric forms. The problem arises when the DNA strands are separated by the helicase enzyme and replication occurs in this state. The research team confirmed that at biological temperatures (around 300K), the thermal equilibrium occupation probability of the tautomer reaches an astoundingly high value of 1.73 × 10⁻⁴. This is significantly higher than the previously known natural spontaneous mutation rate (about 10⁻⁸), strongly suggesting that tautomerisation via quantum tunneling is a substantial and crucial cause of point mutations. ■ Presenting a New Paradigm in Life Sciences This study is a monumental achievement proving that genetic stability and the mutation process—the most fundamental and secretive domain of life—are not accidental chemical mistakes but are directly driven by the probability of quantum tunneling, a physical law of the microscopic world. This is a powerful demonstration that overturns the conventional view of interpreting biological phenomena solely through macroscopic molecular structures and chemical bonds, showing that quantum mechanics can be the key to fully explaining genetic mutation models.
Abstract This study introduces a geometric framework to explain how quantum particles, specifically protons, move through energy barriers in biological molecules like DNA. Rather than viewing this tunneling as a purely random event, we propose that it is governed by the structural complexity of the surrounding molecular environment. By treating the energy landscape as a geometric shape, we demonstrate that the environment acts as a regulator that either facilitates or hinders the movement of protons between genetic base pairs. We applied this model to compare the two primary building blocks of the DNA ladder: the Guanine-Cytosine (G-C) and Adenine-Thymine (A-T) pairs. Our findings reveal that the G-C pair possesses a structural configuration that makes proton movement significantly more likely compared to the A-T pair. This difference provides a clear physical explanation for why certain parts of our genetic code are more prone to spontaneous changes, or tautomeric shifts, which can lead to mutations. Furthermore, the research explores how the DNA molecule interacts with its surrounding cellular noise (e.g. water molecules and proteins). We find that the proton behaves in a hybrid manner (at times acting like a coherent wave that exists in multiple places at once), and at other times like a solid particle trapped by its environment. This dual behavior suggests that life operates at a delicate balance between quantum mechanical effects and classical stability.
A study published on bioRxiv demonstrated that quantum tunneling plays a key role in in vitro hydrolytic enzyme reactions by analyzing kinetic isotope effects (KIE) through deuterium substitution. The involvement of the quantum tunneling effect was confirmed through temperature dependence experiments in major biochemical reactions such as SIRT3-mediated deacetylation, I-SceI-mediated DNA cleavage, and caspase-3-mediated protein cleavage. By observing that DNA homologous recombinational (HR) repair in living cells is almost completely inhibited in a deuterium environment that lowers the probability of quantum tunneling, it was demonstrated that quantum effects dominate cell survival itself. [Quantum Biology Society] Behind life phenomena lies a strange quantum world that cannot be explained by classical mechanics. A prime example is quantum tunneling, where particles pass through reaction energy barriers as if by magic. While it has been known that quantum tunneling contributes to speeding up some enzyme reactions inside proteins , there has been a lack of concrete empirical evidence as to whether this is an essential physical requirement directly linked to actual cell survival. Recently, a groundbreaking study was published showing that if the quantum tunneling effect is inhibited, the cell's life support system itself completely halts. The paper titled "Cell viability is dominated by quantum effects," published on the preprint repository bioRxiv, strongly supports this. A multi-institutional joint research team, including Takeshi Yasuda from the National Institutes for Quantum and Radiological Sciences and Technology (QST) and Kobe University in Japan, led this innovative research. ■ The Link Between Enzyme Hydrolysis and Quantum Tunneling The research team utilized deuterium, an isotope of hydrogen, to track how quantum tunneling is involved in enzymatic chemical reactions. In a heavy deuterium environment, the probability of quantum tunneling is significantly lower compared to light hydrogen, and the research team precisely measured the resulting kinetic isotope effects (KIE) and their temperature dependence. Experimental results proved that the quantum tunneling effect is deeply involved in in vitro hydrolysis reactions essential for cellular metabolism, such as SIRT3-mediated deacetylation, I-SceI-mediated DNA cleavage, and caspase-3-mediated protein cleavage, as evidenced by the disappearance of the isotope effect above specific temperatures. ■ A Halted DNA Repair System Furthermore, the research team directly investigated the impact of the quantum characteristics of these enzyme reactions on living cells. When human cells were exposed to a deuterium-substituted (D₂O) medium environment that artificially lowered the probability of quantum tunneling, it was observed that DNA homologous recombinational (HR) repair, one of the core survival mechanisms of cells, was almost completely inhibited. This means that the most important biochemical repair process protecting and maintaining the genetic information of organisms undergoes a chain reaction of several enzymes and cannot function normally without quantum tunneling phenomena. ■ Quantum Effects Dominating Cell Viability This study empirically demonstrates that core biochemical reactions in living organisms do not simply rely on thermodynamic energy but are fundamentally indebted to quantum mechanical tunneling phenomena. The discovery that numerous hydrolysis and repair reactions performed by enzymes within cells are ultimately strictly dominated by quantum effects serves as crucial evidence that rewrites life phenomena from a purely quantum physics perspective. https://www.biorxiv.org/content/10.1101/2023.07.18.549596v1
In this work we compare two theoretical approaches to modeling the action of the environment on an open quantum system. It is often assumed that as the temperature of the environment surrounding a quantum system increases, so does the speed of environment-induced dephasing, or decoherence (dynamical noise), and so the efficacy of processes such as quantum tunneling drops. An alternative way of viewing the action of the environment is to consider it as carrying out von Neumann--type measurements that, in the limit of continuous observation, lead to the so-called quantum Zeno effect, whereby the system is never allowed to evolve because its wave function is collapsed to its initial state with overwhelming likelihood. However, it has been established in recent years that under certain conditions quantum processes such as tunneling can actually be enhanced (thermally assisted) when the system couples to its environment, as this allows transitions to higher-energy eigenstates closer to the top of the potential barrier. Here we show that, over a specific temperature range, increasing the temperature of the heat bath to encourage such thermally induced tunneling is equivalent to increasing the frequency of a von Neumann--type measurement on the system by the environment (an anti-Zeno effect). However, this correspondence between these two independent pictures of quantum measurement breaks down above a certain limit: Increasing the frequency of measurement above this limit leads to a reversal from an anti-Zeno to a Zeno effect and the tunneling rate decreases again, whereas raising the temperature further leads to a leveling off in the tunneling probability.
Proton transfer plays a key role in the applications of advanced energy materials as well as in the functionalities of biological systems. In this work, based on the transfer matrix method, we study the quantum effects of proton transfer in a series of one-dimensional (1D) model potentials and numerically calculate the quantum probability of transferring across single and double barriers (wells). In the case of single barriers, when the incident energies of protons are above the barrier height, the quantum oscillations in the transmission coefficients depend on the geometric shape of the barriers. It is found that atomic resonant tunneling (ART) not only presents in the rectangular single well and rectangular double barriers as expected, but also exists in the other types of potential wells and double barriers. For hetero-structured double barriers, there is no resonant tunneling in the classical forbidden zone, i.e., in the case when the incident energy (E i) is lower than the barrier height (E b). Furthermore, we have provided generalized analysis on the characteristics of transmission coefficients of hetero-structured rectangular double barriers.