Magnetic Field Effects in Quantum Biology: Beyond the Radical Pair Mechanism
Lead Research Organisation:
UNIVERSITY OF EXETER
Department Name: Engineering Computer Science and Maths
Abstract
In chemical reactions involving transient radical pairs, quantum effects induce a remarkable sensitivity to the intensity and/or orientation of external static magnetic fields as weak as the Earth's magnetic field. The governing principle of all these phenomena is the magnetic-field dependent interconversion between quantum-coherent and often entangled states of electronic spin pairs. Typically this process involves the formation of radical pairs by photo-induced electron transfer reactions, the coherent evolution of the resulting non-equilibrium electron spin states, and spin-selective recombination of the radicals. The effect has attracted widespread interest from the scientific community and general audiences owing to its putative relevance to animal magnetoreception, most notably in migratory birds, its link to possibly adverse effects of weak electromagnetic fields on human health, and the opportunity to increase the efficiency of photovoltaic devices.
While magnetic field effects (MFEs) resulting from the radical pair mechanism (RPM) have been experimentally confirmed in model systems, they are often found to be small (1 % or less in the low-field region). In the framework of this project, we will theoretically investigate the exploitation of quantum phenomena to amplify MFEs or tailor their characteristics to particular applications. The candidate will focus on several mechanisms, most of which are utterly unexplored in this context: the effects of noise resulting from the stochastic modulation of the exchange and electron dipolar interaction by thermal motion; the accumulation of non-equilibrium nuclear polarizations over the course of several excitation cycles by a process known as three-spin mixing; and the amplification of MFEs by scavenging reactions with quenchers of non-zero spin multiplicity (chemical Zeno effect). This project will also address the mysterious observation that the magnetic compass of birds is disrupted by feeble radiofrequency magnetic fields. Currently this phenomenon can only be explained by assuming excessively long spin coherence times, which appear unphysical in noisy biological environments.
The candidate will develop the theoretical models and numerical tools needed to provide a deep understanding of the underlying quantum physics and enable potential technological applications of the RPM in fields ranging from quantum biology (avian quantum compass) to material science (sensor applications).
While magnetic field effects (MFEs) resulting from the radical pair mechanism (RPM) have been experimentally confirmed in model systems, they are often found to be small (1 % or less in the low-field region). In the framework of this project, we will theoretically investigate the exploitation of quantum phenomena to amplify MFEs or tailor their characteristics to particular applications. The candidate will focus on several mechanisms, most of which are utterly unexplored in this context: the effects of noise resulting from the stochastic modulation of the exchange and electron dipolar interaction by thermal motion; the accumulation of non-equilibrium nuclear polarizations over the course of several excitation cycles by a process known as three-spin mixing; and the amplification of MFEs by scavenging reactions with quenchers of non-zero spin multiplicity (chemical Zeno effect). This project will also address the mysterious observation that the magnetic compass of birds is disrupted by feeble radiofrequency magnetic fields. Currently this phenomenon can only be explained by assuming excessively long spin coherence times, which appear unphysical in noisy biological environments.
The candidate will develop the theoretical models and numerical tools needed to provide a deep understanding of the underlying quantum physics and enable potential technological applications of the RPM in fields ranging from quantum biology (avian quantum compass) to material science (sensor applications).
People |
ORCID iD |
Daniel Kattnig (Primary Supervisor) | |
Robert Keens (Student) |
Publications
Keens R
(2020)
Monte-Carlo wavefunction approach for the spin dynamics of recombining radicals
in New Journal of Physics
Keens RH
(2021)
How symmetry-breaking can amplify the magnetosensitivity of dipolarly coupled n-radical systems.
in The Journal of chemical physics
Keens RH
(2018)
Magnetosensitivity in Dipolarly Coupled Three-Spin Systems.
in Physical review letters
Sampson C
(2019)
On the magnetosensitivity of lipid peroxidation: two- versus three-radical dynamics.
in Physical chemistry chemical physics : PCCP
Studentship Projects
Project Reference | Relationship | Related To | Start | End | Student Name |
---|---|---|---|---|---|
EP/N509656/1 | 30/09/2016 | 29/09/2021 | |||
1917982 | Studentship | EP/N509656/1 | 30/09/2017 | 30/07/2021 | Robert Keens |
Description | The effects of the Earth's magnetic field on biological systems can be amplified, and have a significant impact upon intracellular chemistry. The 'hot, noisy' environment of biological systems can actually enhance these effects, not destroy them as traditionally thought. We have developed mathematical models that allow the simulation of ever-more realistic biological systems, and bring us closer to understanding the interplay between magnetism and biology. |
Exploitation Route | The results of this project, and my supervisor Dr Daniel Kattnig's ongoing research, are applicable to the healthcare and pharmaceutical industry, as they could lead to a new form of non-invasive therapeutic techniques based on magnetism and radical reactions. Further, this research has applications for quantum navigation and device building and could be used to design a compass that mimics the sensitivity of the avian magnetic compass. |
Sectors | Aerospace Defence and Marine Healthcare Manufacturing including Industrial Biotechology Pharmaceuticals and Medical Biotechnology |
Description | Since presenting at Pint of Science in 2019, a general public outreach event, it seems people are starting to question the constant exposure to weak magnetic fields (through devices, for example the smartphone in your pocket) and reading into the literature independently to think in an informed way about the potential impacts to health of constant exposure, and maybe scheduling device-breaks into their days. Also, they were interested in the idea of new non-invasive therapeutic techniques that could potentially be developed using magnetism. It was only through Pint of Science that I was able to measure this impact directly, as people came and spoke to me, asked lots of questions, and expressed their interest in thinking about the matter more - I directed them to some of the literature that is easier to digest for a non-specialist and encouraged them to keep learning. |
First Year Of Impact | 2020 |
Sector | Education,Healthcare |
Impact Types | Societal |
Description | Explaining the avian compass through sustained quantum dynamics in driven, open three-radical systems |
Amount | £202,263 (GBP) |
Funding ID | EP/V047175/1 |
Organisation | Engineering and Physical Sciences Research Council (EPSRC) |
Sector | Public |
Country | United Kingdom |
Start | 03/2021 |
End | 09/2022 |
Description | Research Grant |
Amount | £226,604 (GBP) |
Funding ID | RPG-2020-261 |
Organisation | The Leverhulme Trust |
Sector | Charity/Non Profit |
Country | United Kingdom |
Start | 03/2021 |
End | 02/2024 |
Title | New mechanism of magnetosensitivity of radical reactions |
Description | We have suggested a hitherto unknown, mechanism explaining the magnetosensitivity of radical reactions. According to the new mechanism magnetic field effects can arise from the mutual electron-electron dipolar coupling in radical encounters in the presence of a, possibly remote, third radical. In contrast to the conventional radical pair mechanism, this process elicits magnetosensitivity even in the absence of hyperfine interactions. We have demonstrated that the third radical, to some degree, immunizes the magnetic field effect to large exchange interactions and can give rise to a novel low-field effect. Our results provide a more complete picture of the spin dynamical processes that underpin the remarkable magnetosensitivity of radical reactions, in general, and those relevant to lipid autoxidation, in particular. The new three-radical process has further-more the unique property of an intrinsic concentration dependence of the magnetic field effects, which is so far unheard of in the field. |
Type Of Material | Model of mechanisms or symptoms - in vitro |
Year Produced | 2019 |
Provided To Others? | Yes |
Impact | We are not aware of impacts that may have arisen from applying the mechanism so far. However, we rest assured that new studies will be instigated based on our predictive tools. |
Title | DnM |
Description | A generalisation of the D3M model (moving on from the traditional radical pair mechanism for the spin dynamics of biologically relevant radicals) to systems of n > 3 radicals. |
Type Of Material | Computer model/algorithm |
Year Produced | 2021 |
Provided To Others? | Yes |
Impact | The effects of symmetry in radical reactions have been shown to be significant using this model. We have also been able to show that the D3M model we proposed to move on from the very special case of the dyadic radical pair mechanism, originally used as the field-standard, is not itself another special case and is applicable to larger systems - the traditional RPM was not. |
Title | Lipid Peroxidation Model |
Description | Model for the effects of weak magnetic fields on lipid peroxidation reactions. |
Type Of Material | Computer model/algorithm |
Year Produced | 2019 |
Provided To Others? | Yes |
Impact | The effects of weak magnetic fields on the biochemistry of lipid peroxidation reactions is now better understood, as is the fact that these reactions can be concentration-dependent which was previously thought not to be the case. |
Description | Molecular dynamics simulations to inform spin dyanamic calculations |
Organisation | University of Southern Denmark |
Country | Denmark |
Sector | Academic/University |
PI Contribution | Our research team has contributed a new graph based analysis of structural changes observed in long-time molecular dynamic trajectories and principal component analysis. We have also generated new molecular dynamics data based on protocols provided by our partners at the University of Southern Denmark. |
Collaborator Contribution | We have partnered with the group of Prof. Ilia A. Solov'yov to infer dynamics properties from molecular dynamics data. The Solov'yov group has contributed with computational resources (~£15.3k in-kind contribution) and intellectual input. In particular, they have provided molecular dynamics parametrisations of lipid radicals and molecular dynamics data for the dark state of cryptochrome 4 from the European robin. |
Impact | We have so far published a joint publication and are working towards further publications. |
Start Year | 2018 |
Title | A framwork for spin dynmaics calculations of n radicals |
Description | We have develop a versatile Python framework for the simulation of magnetic field effects resulting from the interaction of several, i.e. more than two, radicals. The program solves the Liouville von-Neumann equation of the spin density operator, augmented by terms accounting for the chemical reactivity and decoherence processes. The program is completely general and, for the first time, allows the simulation of magnetic field effects originating from the interaction of more than two radicals. It is delightfully user-friendly and also comes with a detailed manual. |
Type Of Technology | Software |
Year Produced | 2018 |
Impact | This program is essential for the realization of this research project, as it provides us with a versatile simulation platform that underpins our research. It has not yet been released to the public domain as we are in the process of expanding its scope and optimizing the underlying numerical methods. We plan to release the program subject to an open source license in the near future. |
Description | Pint of Science |
Form Of Engagement Activity | A talk or presentation |
Part Of Official Scheme? | No |
Geographic Reach | Local |
Primary Audience | Public/other audiences |
Results and Impact | A presentation on magnetic field effects due to radical pair reactions has been delivered by Robert Keens, a PhD student working on three-radical effects, to an audience comprising mainly members from the general public at a Pint of Science event in Exeter. Pint of Science is a science festival that aims to communicate contemporary scientific developments to the public in an interesting, engaging and approachable way by bringing scientists to the pub and other accessible places. |
Year(s) Of Engagement Activity | 2019 |