1
|
Hambarde S, Manalo JM, Baskin DS, Sharpe MA, Helekar SA. Spinning magnetic field patterns that cause oncolysis by oxidative stress in glioma cells. Sci Rep 2023; 13:19264. [PMID: 37935811 PMCID: PMC10630398 DOI: 10.1038/s41598-023-46758-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2023] [Accepted: 11/04/2023] [Indexed: 11/09/2023] Open
Abstract
Raising reactive oxygen species (ROS) levels in cancer cells to cause macromolecular damage and cell death is a promising anticancer treatment strategy. Observations that electromagnetic fields (EMF) elevate intracellular ROS and cause cancer cell death, have led us to develop a new portable wearable EMF device that generates spinning oscillating magnetic fields (sOMF) to selectively kill cancer cells while sparing normal cells in vitro and to shrink GBM tumors in vivo through a novel mechanism. Here, we characterized the precise configurations and timings of sOMF stimulation that produce cytotoxicity due to a critical rise in superoxide in two types of human glioma cells. We also found that the antioxidant Trolox reverses the cytotoxic effect of sOMF on glioma cells indicating that ROS play a causal role in producing the effect. Our findings clarify the link between the physics of magnetic stimulation and its mechanism of anticancer action, facilitating the development of a potential new safe noninvasive device-based treatment for GBM and other gliomas.
Collapse
Affiliation(s)
- Shashank Hambarde
- Kenneth R. Peak Center for Brain and Pituitary Tumor Treatment and Research, Houston Methodist Hospital, Houston, TX, USA
- Department of Neurosurgery, Houston Methodist Hospital, Houston, TX, USA
- Houston Methodist Research Institute, Houston, TX, USA
| | - Jeanne M Manalo
- Kenneth R. Peak Center for Brain and Pituitary Tumor Treatment and Research, Houston Methodist Hospital, Houston, TX, USA
- Department of Neurosurgery, Houston Methodist Hospital, Houston, TX, USA
- Houston Methodist Research Institute, Houston, TX, USA
| | - David S Baskin
- Kenneth R. Peak Center for Brain and Pituitary Tumor Treatment and Research, Houston Methodist Hospital, Houston, TX, USA
- Department of Neurosurgery, Houston Methodist Hospital, Houston, TX, USA
- Houston Methodist Research Institute, Houston, TX, USA
- Department of Neurosurgery, Weill Cornell Medical College, New York, NY, USA
| | - Martyn A Sharpe
- Kenneth R. Peak Center for Brain and Pituitary Tumor Treatment and Research, Houston Methodist Hospital, Houston, TX, USA
- Department of Neurosurgery, Houston Methodist Hospital, Houston, TX, USA
- Houston Methodist Research Institute, Houston, TX, USA
| | - Santosh A Helekar
- Kenneth R. Peak Center for Brain and Pituitary Tumor Treatment and Research, Houston Methodist Hospital, Houston, TX, USA.
- Department of Neurosurgery, Houston Methodist Hospital, Houston, TX, USA.
- Houston Methodist Research Institute, Houston, TX, USA.
- Department of Neurosurgery, Weill Cornell Medical College, New York, NY, USA.
| |
Collapse
|
2
|
Hong G, Pachter R. Effects of inter-radical interactions and scavenging radicals on magnetosensitivity: spin dynamics simulations of proposed radical pairs. EUROPEAN BIOPHYSICS JOURNAL : EBJ 2023; 52:27-37. [PMID: 36792823 DOI: 10.1007/s00249-023-01630-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/07/2022] [Revised: 01/22/2023] [Accepted: 01/23/2023] [Indexed: 02/17/2023]
Abstract
Although the magnetosensitivity to weak magnetic fields, such as the geomagnetic field, which was exhibited by radical pairs that are potentially responsible for avian navigation, has been previously investigated by spin dynamics simulations, understanding this behavior for proposed radical pairs in other species is limited. These include, for example, radical pairs formed in the single-cell green alga Chlamydomonas reinhardtii (CraCRY) and in Columba livia (ClCRY4). In addition, the radical pair of FADH• with the one-electron reduced cyclobutane thymine dimer that was shown to be sensitive to weak magnetic fields has been of interest. In this work, we investigated the directional magnetosensitivity of these radical pairs to a weak magnetic field by spin dynamics simulations. We find significant reduction in the magnetosensitivity by inclusion of dipolar and exchange interactions, which can be mitigated by a scavenging radical, as demonstrated for the [FAD•- TyrD•] radical pair in CraCRY, but not for the [FADH• T□T•-] radical pair because of the large exchange coupling. The directional magnetosensitivity of the ClCRY4 [FAD•- TyrE•] radical pair can survive this adverse effect even without the scavenging reaction, possibly motivating further experimental exploration.
Collapse
Affiliation(s)
- Gongyi Hong
- Air Force Research Laboratory, Materials and Manufacturing Directorate, Wright-Patterson Air Force Base, Ohio, 45433, USA
| | - Ruth Pachter
- Air Force Research Laboratory, Materials and Manufacturing Directorate, Wright-Patterson Air Force Base, Ohio, 45433, USA.
| |
Collapse
|
3
|
Tiwari Y, Poonia VS. Role of chiral-induced spin selectivity in the radical pair mechanism of avian magnetoreception. Phys Rev E 2022; 106:064409. [PMID: 36671157 DOI: 10.1103/physreve.106.064409] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2022] [Accepted: 12/11/2022] [Indexed: 06/17/2023]
Abstract
In this paper, we investigate the effect of chiral-induced spin selectivity (CISS) on the radical pair mechanism of avian magnetoreception. We examine the impact of spin selectivity on the avian compass sensitivity. In this analysis, we also consider the dipolar and exchange interactions and observe their interplay with CISS. We find that CISS results in a multifold increase in avian compass sensitivity. Interestingly, we also observe that CISS can counter the deleterious effect of dipolar interaction and increase system sensitivity. The analysis has been performed for the toy model (only one nucleus) and a more general case where we consider up to six nuclei from the cryptochrome radical pair system. We observe that the CISS allows the radical pair model to have more realistic recombination rates with good sensitivity. We also do an analysis of the functional window of the avian compass reported in behavioral experiments in the functional window. We could not find a parameter set where a functional window can be observed along with CISS. We also show the effect of spin relaxation on the system and show that under relaxation, CISS shows increased compass sensitivity compared to no CISS case.
Collapse
Affiliation(s)
- Yash Tiwari
- Department of Electronics and Communication, Indian Institute of Technology, Roorkee, Uttrakhand 247667, India
| | - Vishvendra Singh Poonia
- Department of Electronics and Communication, Indian Institute of Technology, Roorkee, Uttrakhand 247667, India
| |
Collapse
|
4
|
Smith LD, Chowdhury FT, Peasgood I, Dawkins N, Kattnig DR. Driven Radical Motion Enhances Cryptochrome Magnetoreception: Toward Live Quantum Sensing. J Phys Chem Lett 2022; 13:10500-10506. [PMID: 36332112 PMCID: PMC9677492 DOI: 10.1021/acs.jpclett.2c02840] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2022] [Accepted: 10/25/2022] [Indexed: 06/16/2023]
Abstract
The mechanism underlying magnetoreception has long eluded explanation. A popular hypothesis attributes this sense to the quantum coherent spin dynamics and spin-selective recombination reactions of radical pairs in the protein cryptochrome. However, concerns about the validity of the hypothesis have been raised because unavoidable inter-radical interactions, such as the strong electron-electron dipolar coupling, appear to suppress its sensitivity. We demonstrate that sensitivity can be restored by driving the spin system through a modulation of the inter-radical distance. It is shown that this dynamical process markedly enhances geomagnetic field sensitivity in strongly coupled radical pairs via Landau-Zener-Stückelberg-Majorana transitions between singlet and triplet states. These findings suggest that a "live" harmonically driven magnetoreceptor can be more sensitive than its "dead" static counterpart.
Collapse
|
5
|
Janitz E, Herb K, Völker LA, Huxter WS, Degen CL, Abendroth JM. Diamond surface engineering for molecular sensing with nitrogen-vacancy centers. JOURNAL OF MATERIALS CHEMISTRY. C 2022; 10:13533-13569. [PMID: 36324301 PMCID: PMC9521415 DOI: 10.1039/d2tc01258h] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/28/2022] [Accepted: 08/06/2022] [Indexed: 05/20/2023]
Abstract
Quantum sensing using optically addressable atomic-scale defects, such as the nitrogen-vacancy (NV) center in diamond, provides new opportunities for sensitive and highly localized characterization of chemical functionality. Notably, near-surface defects facilitate detection of the minute magnetic fields generated by nuclear or electron spins outside of the diamond crystal, such as those in chemisorbed and physisorbed molecules. However, the promise of NV centers is hindered by a severe degradation of critical sensor properties, namely charge stability and spin coherence, near surfaces (< ca. 10 nm deep). Moreover, applications in the chemical sciences require methods for covalent bonding of target molecules to diamond with robust control over density, orientation, and binding configuration. This forward-looking Review provides a survey of the rapidly converging fields of diamond surface science and NV-center physics, highlighting their combined potential for quantum sensing of molecules. We outline the diamond surface properties that are advantageous for NV-sensing applications, and discuss strategies to mitigate deleterious effects while simultaneously providing avenues for chemical attachment. Finally, we present an outlook on emerging applications in which the unprecedented sensitivity and spatial resolution of NV-based sensing could provide unique insight into chemically functionalized surfaces at the single-molecule level.
Collapse
Affiliation(s)
- Erika Janitz
- Department of Physics, ETH Zürich Otto-Stern-Weg 1 8093 Zürich Switzerland
| | - Konstantin Herb
- Department of Physics, ETH Zürich Otto-Stern-Weg 1 8093 Zürich Switzerland
| | - Laura A Völker
- Department of Physics, ETH Zürich Otto-Stern-Weg 1 8093 Zürich Switzerland
| | - William S Huxter
- Department of Physics, ETH Zürich Otto-Stern-Weg 1 8093 Zürich Switzerland
| | - Christian L Degen
- Department of Physics, ETH Zürich Otto-Stern-Weg 1 8093 Zürich Switzerland
| | - John M Abendroth
- Department of Physics, ETH Zürich Otto-Stern-Weg 1 8093 Zürich Switzerland
| |
Collapse
|
6
|
Al Said T, Weber S, Schleicher E. OOP-ESEEM Spectroscopy: Accuracies of Distances of Spin-Correlated Radical Pairs in Biomolecules. Front Mol Biosci 2022; 9:890826. [PMID: 35813811 PMCID: PMC9262093 DOI: 10.3389/fmolb.2022.890826] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2022] [Accepted: 05/05/2022] [Indexed: 11/30/2022] Open
Abstract
In addition to the commonly used electron-electron double resonance (ELDOR) technique, there are several other electron paramagnetic resonance (EPR) methods by which structure information can be obtained by exploiting the dipolar coupling between two radicals based on its characteristic r -3 dependence. In this contribution, we explore the potential of out-of-phase-electron-spin echo envelope modulation (OOP-ESEEM) spectroscopy to collect accurate distance information in photo-sensitive (bio) molecules. Although the method has already been applied to spin-correlated radical pairs in several classes of light-active proteins, the accuracy of the information obtained has not yet been extensively evaluated. To do this in a system-independent fashion, OOP-ESEEM time traces simulated with different values of the dipolar and exchange couplings were generated and analyzed in a best-possible way. Excellent agreement between calculated and numerically fitted values over a wide range of distances (between 15 and 45 Å) was obtained. Furthermore, the limitations of the method and the dependence on various experimental parameters could be evaluated.
Collapse
Affiliation(s)
| | | | - Erik Schleicher
- Institute of Physical Chemistry, University of Freiburg, Freiburg, Germany
| |
Collapse
|
7
|
Babcock N, Kattnig DR. Radical Scavenging Could Answer the Challenge Posed by Electron-Electron Dipolar Interactions in the Cryptochrome Compass Model. JACS AU 2021; 1:2033-2046. [PMID: 34841416 PMCID: PMC8611662 DOI: 10.1021/jacsau.1c00332] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 07/29/2021] [Indexed: 06/13/2023]
Abstract
Many birds are endowed with a visual magnetic sense that may exploit magnetosensitive radical recombination processes in the protein cryptochrome. In this widely accepted but unproven model, geomagnetic sensitivity is suggested to arise from variations in the recombination rate of a pair of radicals, whose unpaired electron spins undergo coherent singlet-triplet interconversion in the geomagnetic field by coupling to nuclear spins via hyperfine interactions. However, simulations of this conventional radical pair mechanism (RPM) predicted only tiny magnetosensitivities for realistic conditions because the RPM's directional sensitivity is strongly suppressed by the intrinsic electron-electron dipolar (EED) interactions, casting doubt on its viability as a magnetic sensor. We show how this RPM-suppression problem is overcome in a three-radical system in which a third "scavenger" radical reacts with one member of the primary pair. We use this finding to predict substantial magnetic field effects that exceed those of the RPM in the presence of EED interactions in animal cryptochromes.
Collapse
Affiliation(s)
- Nathan
Sean Babcock
- Quantum
Biology Laboratory, Howard University, 2400 Sixth Street NW, Washington District of Columbia, 20059, United States of America
- Living
Systems Institute and Department of Physics University of Exeter, Stocker Road, Exeter, EX4 4QD, United Kingdom
| | - Daniel R. Kattnig
- Living
Systems Institute and Department of Physics University of Exeter, Stocker Road, Exeter, EX4 4QD, United Kingdom
| |
Collapse
|
8
|
Low magnetic field effects on a photoinduced electron transfer reaction in an ionic liquid. Chem Phys Lett 2021. [DOI: 10.1016/j.cplett.2021.138569] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
|
9
|
Iwamoto KS, Sandstrom RE, Bryan M, Liu Y, Elgart SR, Sheng K, Steinberg ML, McBride WH, Low DA. Weak Magnetic Fields Enhance the Efficacy of Radiation Therapy. Adv Radiat Oncol 2021; 6:100645. [PMID: 33748547 PMCID: PMC7966835 DOI: 10.1016/j.adro.2021.100645] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2020] [Accepted: 12/02/2020] [Indexed: 11/17/2022] Open
Abstract
Purpose The clinical efficacy of radiation therapy is mechanistically linked to ionization-induced free radicals that cause cell and tissue injury through direct and indirect mechanisms. Free radical reaction dynamics are influenced by many factors and can be manipulated by static weak magnetic fields (WMF) that perturb singlet-triplet state interconversion. Our study exploits this phenomenon to directly increase ionizing radiation (IR) dose absorption in tumors by combining WMF with radiation therapy as a new and effective method to improve treatment. Methods and Materials Coils were custom made to produce both homogeneous and gradient magnetic fields. The gradient coil enabled simultaneous in vitro assessment of free radical/reactive oxygen species reactivity across multiple field strengths from 6 to 66 G. First, increases in IR-induced free radical concentrations using oxidant-sensitive fluorescent dyes in a cell-free system were measured and verified. Next, human and murine cancer cell lines were evaluated in in vitro and in vivo models after exposure to clinically relevant doses of IR in combination with WMF. Results Cellular responses to IR and WMF were field strength and cell line dependent. WMF was able to enhance IR effects on reactive oxygen species formation, DNA double-strand break formation, cell death, and tumor growth. Conclusions We demonstrate that the external presence of a magnetic field enhances radiation-induced cancer cell injury and death in vitro and in vivo. The effect extends beyond the timeframe when free radicals are induced in the presence of radiation into the window when endogenous free radicals are produced and therefore extends the applicability of this novel adjunct to cancer therapy in the context of radiation treatment.
Collapse
Affiliation(s)
- Keisuke S Iwamoto
- Department of Radiation Oncology, David Geffen School of Medicine at UCLA, Los Angeles, California
| | | | - Mark Bryan
- Mark Bryan & Company LLC, Arcadia, California
| | - Yue Liu
- Department of Radiation Oncology, David Geffen School of Medicine at UCLA, Los Angeles, California
| | - S Robin Elgart
- Department of Radiation Oncology, David Geffen School of Medicine at UCLA, Los Angeles, California
| | - Ke Sheng
- Department of Radiation Oncology, David Geffen School of Medicine at UCLA, Los Angeles, California
| | - Michael L Steinberg
- Department of Radiation Oncology, David Geffen School of Medicine at UCLA, Los Angeles, California
| | - William H McBride
- Department of Radiation Oncology, David Geffen School of Medicine at UCLA, Los Angeles, California
| | - Daniel A Low
- Department of Radiation Oncology, David Geffen School of Medicine at UCLA, Los Angeles, California
| |
Collapse
|
10
|
Miura T. Studies on coherent and incoherent spin dynamics that control the magnetic field effect on photogenerated radical pairs. Mol Phys 2019. [DOI: 10.1080/00268976.2019.1643510] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Affiliation(s)
- Tomoaki Miura
- Department of Science, Niigata University, Niigata, Japan
| |
Collapse
|
11
|
Keens RH, Bedkihal S, Kattnig DR. Magnetosensitivity in Dipolarly Coupled Three-Spin Systems. PHYSICAL REVIEW LETTERS 2018; 121:096001. [PMID: 30230901 DOI: 10.1103/physrevlett.121.096001] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/08/2018] [Indexed: 06/08/2023]
Abstract
The radical pair mechanism is a canonical model for the magnetosensitivity of chemical reaction processes. The key ingredient of this model is the hyperfine interaction that induces a coherent mixing of singlet and triplet electron spin states in pairs of radicals, thereby facilitating magnetic field effects (MFEs) on reaction yields through spin-selective reaction channels. We show that the hyperfine interaction is not a categorical requirement to realize the sensitivity of radical reactions to weak magnetic fields. We propose that, in systems comprising three instead of two radicals, dipolar interactions provide an alternative pathway for MFEs. By considering the role of symmetries and energy level crossings, we present a model that demonstrates a directional sensitivity to fields weaker than the geomagnetic field and remarkable spikes in the reaction yield as a function of the magnetic field intensity; these effects can moreover be tuned by the exchange interaction. Our results further the current understanding of the effects of weak magnetic fields on chemical reactions, could pave the way to a clearer understanding of the mysteries of magnetoreception and other biological MFEs and motivate the design of quantum sensors. Further still, this phenomenon will affect spin systems used in quantum information processing in the solid state and may also be applicable to spintronics.
Collapse
Affiliation(s)
- Robert H Keens
- Living Systems Institute and Department of Physics, University of Exeter, Stocker Road, Exeter, Devon, EX4 4QD, United Kingdom
| | - Salil Bedkihal
- Living Systems Institute and Department of Physics, University of Exeter, Stocker Road, Exeter, Devon, EX4 4QD, United Kingdom
| | - Daniel R Kattnig
- Living Systems Institute and Department of Physics, University of Exeter, Stocker Road, Exeter, Devon, EX4 4QD, United Kingdom
| |
Collapse
|
12
|
Hoang HM, Pham VTB, Grampp G, Kattnig DR. Magnetic Field-Sensitive Radical Pair Dynamics in Polymethylene Ether-Bridged Donor-Acceptor Systems. ACS OMEGA 2018; 3:10296-10305. [PMID: 30198006 PMCID: PMC6120740 DOI: 10.1021/acsomega.8b01232] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/04/2018] [Accepted: 08/20/2018] [Indexed: 05/13/2023]
Abstract
Donor-acceptor systems forming exciplexes are versatile models for the study of magnetic field effects (MFEs) on charge recombination reactions. The MFEs originate from singlet-triplet interconversion within transient radical ion pairs (RIPs), which exist in a dynamic equilibrium with the exciplexes. Here, we describe the synthesis and MFEs of the chain-linked N,N-dimethylaniline (DMA)/9-methylanthracene (MAnt) donor-acceptor system MAnt-(CH2) n -O-CH2-CH2-DMA for n = 6, 8, 10, and 16. The MFEs are found to increase with increasing chain length. Effects as large as 37.5% have been observed for the long-chain compound with n = 16. The solvent dependence of the MFEs at magnetic field intensity 75 mT is reported. For the range of solvent static dielectric constants εs = 6.0-36.0, the MFEs go through a maximum for intermediate polarities, for which the direct formation of RIPs prevails and their dissociation and reencounter are balanced. Field-resolved measurements (MARY spectra) are reported for solutions in butyronitrile. The MARY spectra reveal that for n = 8, 10, 16, the average exchange interaction is negligible during the coherent lifetime of the radical pair. However, singlet-triplet dephasing broadens the lineshape; the shorter the linker, the more pronounced this effect is. For n = 6, a dip in the fluorescence intensity reveals a nonzero average exchange coupling of the order of ±5 mT. We discuss the field-dependence in the framework of the semiclassical theory taking spin-selective recombination, singlet-triplet dephasing, and exchange coupling into account. Singlet recombination rates of the order of 0.1 ns-1 and various degrees of singlet-triplet dephasing govern the spin dynamics. In addition, because of a small free energy gap between the exciplex and the locally excited fluorophore quencher pair, a fully reversible interconversion between the RIP, exciplex, and locally excited fluorophore is revealed by spectrally resolved MFE measurements for the long-chain systems (n = 10, 16).
Collapse
Affiliation(s)
- Hao Minh Hoang
- Ho
Chi Minh City University of Technology and Education, Vo Van Ngan 01, Linh Chieu Ward, Thu Duc District, Ho Chi Minh City 700000, Vietnam
- Institute
of Physical and Theoretical Chemistry, Graz
University of Technology, Stremayrgasse 9/I, A-8010 Graz, Austria
| | - Van Thi Bich Pham
- Institute
of Physical and Theoretical Chemistry, Graz
University of Technology, Stremayrgasse 9/I, A-8010 Graz, Austria
| | - Günter Grampp
- Institute
of Physical and Theoretical Chemistry, Graz
University of Technology, Stremayrgasse 9/I, A-8010 Graz, Austria
| | - Daniel R. Kattnig
- Living
Systems Institute and Department of Physics, University of Exeter, Stocker Road, Exeter, Devon EX4 4QD, United Kingdom
| |
Collapse
|
13
|
Miura T, Murai H. Effect of molecular diffusion on the spin dynamics of a micellized radical pair in low magnetic fields studied by Monte Carlo simulation. J Phys Chem A 2015; 119:5534-44. [PMID: 25942039 DOI: 10.1021/acs.jpca.5b02183] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Magnetic field effect is a powerful tool to study dynamics and kinetics of radical pairs (RPs), which are one of the most important intermediates for organic photon-energy conversion reactions. However, quantitative discussion regarding the relationship between the modulation of interelectron interactions and spin dynamics at low magnetic fields (<10 mT) is still an open question. We have studied the spin dynamics of a long-lived RP in a micelle by newly developed Monte Carlo simulation, in which fluctuations of the exchange and magnetic dipolar interactions by in-cage diffusion are directly introduced to the time-domain spin dynamics calculation. State-dependent relaxation/dephasing times of a few to a few tens of nanoseconds are obtained by simulations without hyperfine interactions (HFIs) as a function of the mutual diffusion constant (∼10(-6) cm(2)/s). Simulations with the HFIs exhibit incoherent singlet-triplet (S-T) mixings resulting from interplay between the HFIs and the fluctuating spin-spin interactions. The experimentally observed incoherent S-T mixing of ∼20 ns at 3 mT for a singlet-born RP in a sodium dodecyl sulfate micelle is reproduced by the simulation with reasonable diffusion coefficients. The computational method developed here contributes to quantitative detection of molecular motion that governs the recombination efficiency of RPs.
Collapse
Affiliation(s)
- Tomoaki Miura
- †Department of Chemistry, Niigata University, 8050 Ikarashi 2-no-cho, Nishi-ku, Niigata 950-2181, Japan
| | - Hisao Murai
- ‡Department of Chemistry, Shizuoka University, 836 Oya, Suruga-ku, Shizuoka 422-8529, Japan
| |
Collapse
|
14
|
Yago T, Wakasa M. A practical approach to calculate the time evolutions of magnetic field effects on photochemical reactions in nano-structured materials. Phys Chem Chem Phys 2015; 17:9737-47. [PMID: 25773238 DOI: 10.1039/c5cp00595g] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
A practical method to calculate time evolutions of magnetic field effects (MFEs) on photochemical reactions involving radical pairs is developed on the basis of the theory of the chemically induced dynamic spin polarization proposed by Pedersen and Freed. In theory, the stochastic Liouville equation (SLE), including the spin Hamiltonian, diffusion motions of the radical pair, chemical reactions, and spin relaxations, is solved by using the Laplace and the inverse Laplace transformation technique. In our practical approach, time evolutions of the MFEs are successfully calculated by applying the Miller-Guy method instead of the final value theorem to the inverse Laplace transformation process. Especially, the SLE calculations are completed in a short time when the radical pair dynamics can be described by the chemical kinetics consisting of diffusions, reactions and spin relaxations. The SLE analysis with a short calculation time enables one to examine the various parameter sets for fitting the experimental date. Our study demonstrates that simultaneous fitting of the time evolution of the MFE and of the magnetic field dependence of the MFE provides valuable information on the diffusion motions of the radical pairs in nano-structured materials such as micelles where the lifetimes of radical pairs are longer than hundreds of nano-seconds and the magnetic field dependence of the spin relaxations play a major role for the generation of the MFE.
Collapse
Affiliation(s)
- Tomoaki Yago
- Department of Chemistry, Graduate School of Science and Engineering, Saitama University, 255 Shimo-ohkubo, Sakura-ku, Saitama 338-8570, Japan.
| | | |
Collapse
|
15
|
Woodbine L, Haines J, Coster M, Barazzuol L, Ainsbury E, Sienkiewicz Z, Jeggo P. The rate of X-ray-induced DNA double-strand break repair in the embryonic mouse brain is unaffected by exposure to 50 Hz magnetic fields. Int J Radiat Biol 2015; 91:495-9. [PMID: 25786477 PMCID: PMC4673581 DOI: 10.3109/09553002.2015.1021963] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Purpose: Following in utero exposure to low dose radiation (10–200 mGy), we recently observed a linear induction of DNA double-strand breaks (DSB) and activation of apoptosis in the embryonic neuronal stem/progenitor cell compartment. No significant induction of DSB or apoptosis was observed following exposure to magnetic fields (MF). In the present study, we exploited this in vivo system to examine whether exposure to MF before and after exposure to 100 mGy X-rays impacts upon DSB repair rates. Materials and methods: 53BP1 foci were quantified following combined exposure to radiation and MF in the embryonic neuronal stem/progenitor cell compartment. Embryos were exposed in utero to 50 Hz MF at 300 μT for 3 h before and up to 9 h after exposure to 100 mGy X-rays. Controls included embryos exposed to MF or X-rays alone plus sham exposures. Results: Exposure to MF before and after 100 mGy X-rays did not impact upon the rate of DSB repair in the embryonic neuronal stem cell compartment compared to repair rates following radiation exposure alone. Conclusions: We conclude that in this sensitive system MF do not exert any significant level of DNA damage and do not impede the repair of X-ray induced damage.
Collapse
Affiliation(s)
- Lisa Woodbine
- Genome Damage and Stability Centre, Life Sciences, University of Sussex , Brighton
| | | | | | | | | | | | | |
Collapse
|
16
|
Qin W, Gong M, Chen X, Shastry TA, Sakidja R, Yuan G, Hersam MC, Wuttig M, Ren S. Multiferroicity of carbon-based charge-transfer magnets. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2015; 27:734-739. [PMID: 25389110 DOI: 10.1002/adma.201403396] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/27/2014] [Revised: 10/10/2014] [Indexed: 06/04/2023]
Abstract
A new type of carbon charge-transfer magnet, consisting of a fullerene acceptor and single-walled carbon nanotube donor, is demonstrated, which exhibits room temperature ferromagnetism and magnetoelectric (ME) coupling. In addition, external stimuli (electric/magnetic/elastic field) and the concentration of a nanocarbon complex enable the tunabilities of the magnetization and ME coupling due to the control of the charge transfer.
Collapse
Affiliation(s)
- Wei Qin
- Department of Chemistry, University of Kansas, Lawrence, KS, 66045, USA
| | | | | | | | | | | | | | | | | |
Collapse
|
17
|
Breynaert E, Emmerich J, Mustafa D, Bajpe SR, Altantzis T, Van Havenbergh K, Taulelle F, Bals S, Van Tendeloo G, Kirschhock CEA, Martens JA. Enhanced self-assembly of metal oxides and metal-organic frameworks from precursors with magnetohydrodynamically induced long-lived collective spin states. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2014; 26:5173-5178. [PMID: 24889049 DOI: 10.1002/adma.201400835] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/21/2014] [Revised: 04/23/2014] [Indexed: 06/03/2023]
Abstract
Magneto-hydrodynamic generation of long-lived collective spin states and their impact on crystal morphology is demonstrated for three different, technologically relevant materials: COK-16 metal organic framework, manganese oxide nanotubes, and vanadium oxide nano-scrolls.
Collapse
Affiliation(s)
- Eric Breynaert
- KU Leuven - Center for Surface, Chemistry and Catalysis (COK), Kasteelpark Arenberg 23 - box 2461, B-3001, Heverlee, Belgium
| | | | | | | | | | | | | | | | | | | | | |
Collapse
|
18
|
Solov'yov IA, Domratcheva T, Schulten K. Separation of photo-induced radical pair in cryptochrome to a functionally critical distance. Sci Rep 2014; 4:3845. [PMID: 24457842 PMCID: PMC4894384 DOI: 10.1038/srep03845] [Citation(s) in RCA: 59] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2013] [Accepted: 12/27/2013] [Indexed: 11/09/2022] Open
Abstract
Cryptochrome is a blue light receptor that acts as a sensor for the geomagnetic field and assists many animals in long-range navigation. The magnetoreceptor function arises from light-induced formation of a radical pair through electron transfer between a flavin cofactor (FAD) and a triad of tryptophan residues. Here, this electron transfer is investigated by quantum chemical and classical molecular dynamics calculations. The results reveal how sequential electron transfer, assisted by rearrangement of polar side groups in the cryptochrome interior, can yield a FAD-Trp radical pair state with the FAD and Trp partners separated beyond a critical distance. The large radical pair separation reached establishes cryptochrome's sensitivity to the geomagnetic field through weakening of distance-dependent exchange and dipole-dipole interactions. It is estimated that the key secondary electron transfer step can overcome in speed both recombination (electron back-transfer) and proton transfer involving the radical pair reached after primary electron transfer.
Collapse
Affiliation(s)
- Ilia A Solov'yov
- 1] Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, 405 N. Mathews Ave, Urbana Illinois 61801, USA [2] Department of Physics, Chemistry and Pharmacy, University of Southern Denmark, Campusvej 55, DK-5230 Odense M, Denmark
| | - Tatiana Domratcheva
- Department of Biomolecular Mechanisms, Max Planck Institute for Medical Research, Jahnstrasse 29, 69120 Heidelberg, Germany
| | - Klaus Schulten
- 1] Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, 405 N. Mathews Ave, Urbana Illinois 61801, USA [2] Department of Physics, University of Illinois at Urbana-Champaign, 1110 W. Green Street, Urbana, Illinois 61801, USA
| |
Collapse
|
19
|
Evans EW, Dodson CA, Maeda K, Biskup T, Wedge CJ, Timmel CR. Magnetic field effects in flavoproteins and related systems. Interface Focus 2013; 3:20130037. [PMID: 24511388 PMCID: PMC3915827 DOI: 10.1098/rsfs.2013.0037] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Within the framework of the radical pair mechanism, magnetic fields may alter the rate and yields of chemical reactions involving spin-correlated radical pairs as intermediates. Such effects have been studied in detail in a variety of chemical systems both experimentally and theoretically. In recent years, there has been growing interest in whether such magnetic field effects (MFEs) also occur in biological systems, a question driven most notably by the increasing body of evidence for the involvement of such effects in the magnetic compass sense of animals. The blue-light photoreceptor cryptochrome is placed at the centre of this debate and photoexcitation of its bound flavin cofactor has indeed been shown to result in the formation of radical pairs. Here, we review studies of MFEs on free flavins in model systems as well as in blue-light photoreceptor proteins and discuss the properties that are crucial in determining the magnetosensitivity of these systems.
Collapse
Affiliation(s)
- Emrys W. Evans
- Centre for Advanced Electron Spin Resonance, Department of Chemistry, University of Oxford, South Parks Road, Oxford OX1 3QR, UK
| | - Charlotte A. Dodson
- Chemistry Research Laboratory, Department of Chemistry, University of Oxford, Mansfield Road, Oxford OX1 3TA, UK
| | - Kiminori Maeda
- Centre for Advanced Electron Spin Resonance, Department of Chemistry, University of Oxford, South Parks Road, Oxford OX1 3QR, UK
| | - Till Biskup
- Institut für Physikalische Chemie, Albert-Ludwigs-Universität Freiburg, Albertstraße 21, 79104 Freiburg, Germany
| | - C. J. Wedge
- Department of Physics, University of Warwick, Gibbet Hill Road, Coventry CV4 7AL, UK
- Physical and Theoretical Chemistry Laboratory, Department of Chemistry, University of Oxford, South Parks Road, Oxford OX1 3QZ, UK
| | - Christiane R. Timmel
- Centre for Advanced Electron Spin Resonance, Department of Chemistry, University of Oxford, South Parks Road, Oxford OX1 3QR, UK
| |
Collapse
|
20
|
Teodorović AV, Badjuk DM, Stevanović N, Pavlović RZ. Stabilization of long-chain intermediates in solution. Octyl radicals and cations. J Mol Struct 2013. [DOI: 10.1016/j.molstruc.2013.02.020] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
|
21
|
Solov’yov IA, Domratcheva T, Shahi ARM, Schulten K. Decrypting cryptochrome: revealing the molecular identity of the photoactivation reaction. J Am Chem Soc 2012; 134:18046-52. [PMID: 23009093 PMCID: PMC3500783 DOI: 10.1021/ja3074819] [Citation(s) in RCA: 86] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Migrating birds fly thousands of miles or more, often without visual cues and in treacherous winds, yet keep direction. They employ for this purpose, apparently as a powerful navigational tool, the photoreceptor protein cryptochrome to sense the geomagnetic field. The unique biological function of cryptochrome supposedly arises from a photoactivation reaction involving radical pair formation through electron transfer. Radical pairs, indeed, can act as a magnetic compass; however, the cryptochrome photoreaction pathway is not fully resolved yet. To reveal this pathway and underlying photochemical mechanisms, we carried out a combination of quantum chemical calculations and molecular dynamics simulations on plant ( Arabidopsis thaliana ) cryptochrome. The results demonstrate that after photoexcitation a radical pair forms, becomes stabilized through proton transfer, and decays back to the protein's resting state on time scales allowing the protein, in principle, to act as a radical pair-based magnetic sensor. We briefly relate our findings on A. thaliana cryptochrome to photoreaction pathways in animal cryptochromes.
Collapse
|
22
|
Consales C, Merla C, Marino C, Benassi B. Electromagnetic fields, oxidative stress, and neurodegeneration. Int J Cell Biol 2012; 2012:683897. [PMID: 22991514 PMCID: PMC3444040 DOI: 10.1155/2012/683897] [Citation(s) in RCA: 109] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2012] [Revised: 06/19/2012] [Accepted: 06/19/2012] [Indexed: 12/21/2022] Open
Abstract
Electromagnetic fields (EMFs) originating both from both natural and manmade sources permeate our environment. As people are continuously exposed to EMFs in everyday life, it is a matter of great debate whether they can be harmful to human health. On the basis of two decades of epidemiological studies, an increased risk for childhood leukemia associated with Extremely Low Frequency fields has been consistently assessed, inducing the International Agency for Research on Cancer to insert them in the 2B section of carcinogens in 2001. EMFs interaction with biological systems may cause oxidative stress under certain circumstances. Since free radicals are essential for brain physiological processes and pathological degeneration, research focusing on the possible influence of the EMFs-driven oxidative stress is still in progress, especially in the light of recent studies suggesting that EMFs may contribute to the etiology of neurodegenerative disorders. This review synthesizes the emerging evidences about this topic, highlighting the wide data uncertainty that still characterizes the EMFs effect on oxidative stress modulation, as both pro-oxidant and neuroprotective effects have been documented. Care should be taken to avoid methodological limitations and to determine the patho-physiological relevance of any alteration found in EMFs-exposed biological system.
Collapse
Affiliation(s)
- Claudia Consales
- Unit of Radiation Biology and Human Health, ENEA-Casaccia, Rome 00123, Italy
| | | | | | - Barbara Benassi
- Unit of Radiation Biology and Human Health, ENEA-Casaccia, Rome 00123, Italy
| |
Collapse
|
23
|
Wagemans W, Schellekens AJ, Kemper M, Bloom FL, Bobbert PA, Koopmans B. Spin-spin interactions in organic magnetoresistance probed by angle-dependent measurements. PHYSICAL REVIEW LETTERS 2011; 106:196802. [PMID: 21668186 DOI: 10.1103/physrevlett.106.196802] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/05/2010] [Indexed: 05/30/2023]
Abstract
The dependence of organic magnetoresistance (OMAR) on the orientation of the magnetic field has been investigated. In contrast with previous claims, a finite and systematic change in magnitude is observed when the orientation of the field is changed with respect to the sample. It is demonstrated that, to explain these effects, spin-spin interactions have to be included in the models previously suggested for OMAR. Dipole coupling and exchange coupling are introduced in combination with either an anisotropy of the orientation of the spin pairs or an anisotropy in the hyperfine fields.
Collapse
Affiliation(s)
- W Wagemans
- Department of Applied Physics, Center for NanoMaterials, Eindhoven University of Technology, P.O. Box 513, 5600 MB Eindhoven, The Netherlands
| | | | | | | | | | | |
Collapse
|
24
|
Ritz T, Ahmad M, Mouritsen H, Wiltschko R, Wiltschko W. Photoreceptor-based magnetoreception: optimal design of receptor molecules, cells, and neuronal processing. J R Soc Interface 2010; 7 Suppl 2:S135-46. [PMID: 20129953 PMCID: PMC2843994 DOI: 10.1098/rsif.2009.0456.focus] [Citation(s) in RCA: 102] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2009] [Accepted: 01/12/2010] [Indexed: 11/12/2022] Open
Abstract
The sensory basis of magnetoreception in animals still remains a mystery. One hypothesis of magnetoreception is that photochemical radical pair reactions can transduce magnetic information in specialized photoreceptor cells, possibly involving the photoreceptor molecule cryptochrome. This hypothesis triggered a considerable amount of research in the past decade. Here, we present an updated picture of the radical-pair photoreceptor hypothesis. In our review, we will focus on insights that can assist biologists in their search for the elusive magnetoreceptors.
Collapse
Affiliation(s)
- Thorsten Ritz
- Department of Physics and Astronomy, University of California at Irvine, Irvine, CA 92697, USA.
| | | | | | | | | |
Collapse
|
25
|
Ritz T, Ahmad M, Mouritsen H, Wiltschko R, Wiltschko W. Photoreceptor-based magnetoreception: optimal design of receptor molecules, cells, and neuronal processing. J R Soc Interface 2010. [PMID: 20129953 DOI: 10.1098/rsif.2009] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
The sensory basis of magnetoreception in animals still remains a mystery. One hypothesis of magnetoreception is that photochemical radical pair reactions can transduce magnetic information in specialized photoreceptor cells, possibly involving the photoreceptor molecule cryptochrome. This hypothesis triggered a considerable amount of research in the past decade. Here, we present an updated picture of the radical-pair photoreceptor hypothesis. In our review, we will focus on insights that can assist biologists in their search for the elusive magnetoreceptors.
Collapse
Affiliation(s)
- Thorsten Ritz
- Department of Physics and Astronomy, University of California at Irvine, Irvine, CA 92697, USA.
| | | | | | | | | |
Collapse
|
26
|
Catallo N, Colacicchi S, Carnicelli V, Giulio AD, Lucari F, Gualtieri G. Static Magnetic Field Effect on the Fremy’s Salt−Ascorbic Acid Chemical Reaction Studied by Continuous-Wave Electron Paramagnetic Resonance. J Phys Chem A 2010; 114:778-83. [DOI: 10.1021/jp906376h] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- N. Catallo
- INFM, Department of Health Sciences, University of L’Aquila, Via Vetoio, Coppito 2, 67100 L’Aquila, Italy, Department of Biomedical Sciences and Technologies, University of L’Aquila, Via Vetoio, Coppito 2, 67100 L’Aquila, Italy, and INFM, Department of Physics, University of L’Aquila, Via Vetoio, Coppito 1, 67100 L’Aquila, Italy
| | - S. Colacicchi
- INFM, Department of Health Sciences, University of L’Aquila, Via Vetoio, Coppito 2, 67100 L’Aquila, Italy, Department of Biomedical Sciences and Technologies, University of L’Aquila, Via Vetoio, Coppito 2, 67100 L’Aquila, Italy, and INFM, Department of Physics, University of L’Aquila, Via Vetoio, Coppito 1, 67100 L’Aquila, Italy
| | - V. Carnicelli
- INFM, Department of Health Sciences, University of L’Aquila, Via Vetoio, Coppito 2, 67100 L’Aquila, Italy, Department of Biomedical Sciences and Technologies, University of L’Aquila, Via Vetoio, Coppito 2, 67100 L’Aquila, Italy, and INFM, Department of Physics, University of L’Aquila, Via Vetoio, Coppito 1, 67100 L’Aquila, Italy
| | - A. Di Giulio
- INFM, Department of Health Sciences, University of L’Aquila, Via Vetoio, Coppito 2, 67100 L’Aquila, Italy, Department of Biomedical Sciences and Technologies, University of L’Aquila, Via Vetoio, Coppito 2, 67100 L’Aquila, Italy, and INFM, Department of Physics, University of L’Aquila, Via Vetoio, Coppito 1, 67100 L’Aquila, Italy
| | - F. Lucari
- INFM, Department of Health Sciences, University of L’Aquila, Via Vetoio, Coppito 2, 67100 L’Aquila, Italy, Department of Biomedical Sciences and Technologies, University of L’Aquila, Via Vetoio, Coppito 2, 67100 L’Aquila, Italy, and INFM, Department of Physics, University of L’Aquila, Via Vetoio, Coppito 1, 67100 L’Aquila, Italy
| | - G. Gualtieri
- INFM, Department of Health Sciences, University of L’Aquila, Via Vetoio, Coppito 2, 67100 L’Aquila, Italy, Department of Biomedical Sciences and Technologies, University of L’Aquila, Via Vetoio, Coppito 2, 67100 L’Aquila, Italy, and INFM, Department of Physics, University of L’Aquila, Via Vetoio, Coppito 1, 67100 L’Aquila, Italy
| |
Collapse
|
27
|
Efimova O, Hore P. Evaluation of nuclear quadrupole interactions as a source of magnetic anisotropy in the radical pair model of the avian magnetic compass. Mol Phys 2009. [DOI: 10.1080/00268970902852624] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
|
28
|
Rodgers CT, Hore PJ. Chemical magnetoreception in birds: the radical pair mechanism. Proc Natl Acad Sci U S A 2009; 106:353-60. [PMID: 19129499 PMCID: PMC2626707 DOI: 10.1073/pnas.0711968106] [Citation(s) in RCA: 314] [Impact Index Per Article: 20.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2008] [Indexed: 11/18/2022] Open
Abstract
Migratory birds travel vast distances each year, finding their way by various means, including a remarkable ability to perceive the Earth's magnetic field. Although it has been known for 40 years that birds possess a magnetic compass, avian magnetoreception is poorly understood at all levels from the primary biophysical detection events, signal transduction pathways and neurophysiology, to the processing of information in the brain. It has been proposed that the primary detector is a specialized ocular photoreceptor that plays host to magnetically sensitive photochemical reactions having radical pairs as fleeting intermediates. Here, we present a physical chemist's perspective on the "radical pair mechanism" of compass magnetoreception in birds. We outline the essential chemical requirements for detecting the direction of an Earth-strength approximately 50 microT magnetic field and comment on the likelihood that these might be satisfied in a biologically plausible receptor. Our survey concludes with a discussion of cryptochrome, the photoactive protein that has been put forward as the magnetoreceptor molecule.
Collapse
Affiliation(s)
- Christopher T. Rodgers
- Department of Chemistry, Physical and Theoretical Chemistry Laboratory, University of Oxford, South Parks Road, Oxford, OX1 3QZ, United Kingdom; and
- Oxford Centre for Clinical Magnetic Resonance Research, Level 0, John Radcliffe Hospital, Oxford, OX3 9DU, United Kingdom
| | - P. J. Hore
- Department of Chemistry, Physical and Theoretical Chemistry Laboratory, University of Oxford, South Parks Road, Oxford, OX1 3QZ, United Kingdom; and
| |
Collapse
|
29
|
Abstract
Chemical reactions that involve radical intermediates can be influenced by magnetic fields, which act to alter their rate, yield, or product distribution. These effects have been studied extensively in liquids, solids, and constrained media such as micelles. They may be interpreted using the radical pair mechanism (RPM). Such effects are central to the field of spin chemistry of which there have been several detailed and extensive reviews. This review instead presents an introductory account of the field of spin chemistry, suitable for use by graduate students or researchers who are new to the area. It proceeds by giving a brief historical overview of the development of spin chemistry, before introducing the essential theory. This is then illustrated by application to a series of recent developments in solution-phase magnetic field effects (MFEs). The closing pages of this review describe the role played by spin chemistry in the remarkable magnetic compass sense of birds and other animals.
Collapse
|
30
|
Miura T, Murai H. Real-time observation of the spin-state mixing process of a micellized radical pair in weak magnetic fields by nanosecond fast field switching. J Phys Chem A 2008; 112:2526-32. [PMID: 18307324 DOI: 10.1021/jp077505x] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The singlet-triplet spin-state mixing process of a singlet-born radical pair confined in a sodium dodecyl sulfate (SDS) micelle was studied by observing the nanosecond switched external magnetic field (SEMF) effect on the transient absorption signals. A long-lived singlet radical pair is generated by the photoinduced bond cleavage reaction of tetraphenylhydrazine in an SDS micelle. Application of off-on type SEMF results in the increase of the free radical yield contrary to the decrease produced by an applied static magnetic field. The S-T mixing process in low magnetic field was observed by means of a delay-shift SEMF experiment. Observed incoherent mixing processes are explained in terms of the interplay between coherent hyperfine interaction and fast dephasing processes caused by the fluctuation of electron-spin interactions. Singlet-triplet and triplet-triplet dephasing rate constants are determined independently to be 2 x 10(8) and 0.2 x 10(8) s(-)1, respectively, by a simulation based on a modified single-site Liouville equation. This is the first direct observation of the incoherent spin-state mixing process at magnetic fields comparable to the hyperfine interactions of the radical pair.
Collapse
Affiliation(s)
- Tomoaki Miura
- Graduate School of Science and Engineering, Faculty of Science, Shizuoka University, 836 Oya, Surugaku, Shizuoka 422-8529, Japan
| | | |
Collapse
|
31
|
Role of exchange and dipolar interactions in the radical pair model of the avian magnetic compass. Biophys J 2007; 94:1565-74. [PMID: 17981903 DOI: 10.1529/biophysj.107.119362] [Citation(s) in RCA: 116] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
It is not yet understood how migratory birds sense the Earth's magnetic field as a source of compass information. One suggestion is that the magnetoreceptor involves a photochemical reaction whose product yields are sensitive to external magnetic fields. Specifically, a flavin-tryptophan radical pair is supposedly formed by photoinduced sequential electron transfer along a chain of three tryptophan residues in a cryptochrome flavoprotein immobilized in the retina. The electron Zeeman interaction with the Earth's magnetic field ( approximately 50 microT), modulated by anisotropic magnetic interactions within the radicals, causes the product yields to depend on the orientation of the receptor. According to well-established theory, the radicals would need to be separated by >3.5 nm in order that interradical spin-spin interactions are weak enough to permit a approximately 50 microT field to have a significant effect. Using quantum mechanical simulations, it is shown here that substantial changes in product yields can nevertheless be expected at the much smaller separation of 2.0 +/- 0.2 nm where the effects of exchange and dipolar interactions partially cancel. The terminal flavin-tryptophan radical pair in cryptochrome has a separation of approximately 1.9 nm and is thus ideally placed to act as a magnetoreceptor for the compass mechanism.
Collapse
|
32
|
Woodward JR, Vink CB. Hyperfine coupling dependence of the effects of weak magnetic fields on the recombination reactions of radicals generated from polymerisation photoinitiators. Phys Chem Chem Phys 2007; 9:6272-8. [PMID: 18046476 DOI: 10.1039/b711635g] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The recombination reactions of free radicals formed from the photolysis of a series of polymerisation photoinitiators were studied using time-resolved infrared spectroscopy. All molecules showed Zeeman magnetic field effects (MFEs) in the field range 0-37 mT and those molecules that produced radical pairs with average hyperfine couplings greater than 5 mT showed substantial inverted field effects at fields of less than 10 mT (so-called low field effects, LFEs). Monte Carlo simulations with full treatment of all the isotropic hyperfine couplings in the spin Hamiltonian reproduced well the observed field effects. The use of the usual analysis based on the calculated B1/2 value for the radical pair was found to be inappropriate in systems with substantial LFEs, but simple correlations between this B1/2 value and the observed field features were established.
Collapse
Affiliation(s)
- Jonathan R Woodward
- Department of Chemistry, University of Leicester, University Road, Leicester, UK.
| | | |
Collapse
|
33
|
Miura T, Maeda K, Arai T. The spin mixing process of a radical pair in low magnetic field observed by transient absorption detected nanosecond pulsed magnetic field effect. J Phys Chem A 2007; 110:4151-6. [PMID: 16553365 DOI: 10.1021/jp056488d] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The spin mixing process of the radical pair in the sodium dodecyl sulfate (SDS) micelle is studied by using a novel technique nanosecond pulsed magnetic field effect on transient absorption. We have developed the equipment for a nanosecond pulsed magnetic field and observed its effect on the radical pair reaction. A decrease of the free radical yield by a reversely directed pulsed magnetic field that cancels static field is observed, and the dependence on its magnitude, which is called pulsed MARY (magnetic field effect on reaction yield) spectra, is studied. The observed spectra reflect the spin mixing in 50-200 ns and show clear time evolution. Theoretical simulation of pulsed MARY spectra based on a single site modified Liouville equation indicates that the fast spin dephasing processes induced by the modulation of electron-electron spin interaction by molecular reencounter affect to the coherent spin mixing by a hyperfine interaction in a low magnetic field.
Collapse
Affiliation(s)
- Tomoaki Miura
- Department of Chemistry, Faculty of Science, Shizuoka University, Ohya 836, Shizuoka City 422-8529, Japan
| | | | | |
Collapse
|
34
|
Solov'yov IA, Chandler DE, Schulten K. Magnetic field effects in Arabidopsis thaliana cryptochrome-1. Biophys J 2007; 92:2711-26. [PMID: 17259272 PMCID: PMC1831705 DOI: 10.1529/biophysj.106.097139] [Citation(s) in RCA: 142] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2006] [Accepted: 01/04/2007] [Indexed: 11/18/2022] Open
Abstract
The ability of some animals, most notably migratory birds, to sense magnetic fields is still poorly understood. It has been suggested that this "magnetic sense" may be mediated by the blue light receptor protein cryptochrome, which is known to be localized in the retinas of migratory birds. Cryptochromes are a class of photoreceptor signaling proteins that are found in a wide variety of organisms and that primarily perform regulatory functions, such as the entrainment of circadian rhythm in mammals and the inhibition of hypocotyl growth in plants. Recent experiments have shown that the activity of cryptochrome-1 in Arabidopsis thaliana is enhanced by the presence of a weak external magnetic field, confirming the ability of cryptochrome to mediate magnetic field responses. Cryptochrome's signaling is tied to the photoreduction of an internally bound chromophore, flavin adenine dinucleotide. The spin chemistry of this photoreduction process, which involves electron transfer from a chain of three tryptophans, can be modulated by the presence of a magnetic field in an effect known as the radical-pair mechanism. Here we present and analyze a model of the flavin-adenine-dinucleotide-tryptophan chain system that incorporates realistic hyperfine coupling constants and reaction rate constants. Our calculations show that the radical-pair mechanism in cryptochrome can produce an increase in the protein's signaling activity of approximately 10% for magnetic fields on the order of 5 G, which is consistent with experimental results. These calculations, in view of the similarity between bird and plant cryptochromes, provide further support for a cryptochrome-based model of avian magnetoreception.
Collapse
Affiliation(s)
- Ilia A Solov'yov
- Frankfurt Institute for Advanced Studies, Johann Wolfgang Goethe University, Frankfurt am Main, Germany
| | | | | |
Collapse
|
35
|
Maeda K, Miura T, Arai T. A practical simulation and a novel insight to the magnetic field effect on a radical pair in a micelle. Mol Phys 2006. [DOI: 10.1080/14767050600588106] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
|
36
|
Suzuki T, Miura T, Maeda K, Arai T. Spin Dynamics of the Radical Pair in a Low Magnetic Field Studied by the Transient Absorption Detected Magnetic Field Effect on the Reaction Yield and Switched External Magnetic Field. J Phys Chem A 2005; 109:9911-8. [PMID: 16838907 DOI: 10.1021/jp053989q] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The spin dynamics of the radical pair generated from the photocleavage reaction of (2,4,6-trimethylbenzoyl)diphenylphosphine oxide (TMDPO) in micellar solutions was studied by the time-resolved magnetic field effect (MFE) on the transient absorption (TA) and by a novel technique, absorption detected switched external magnetic field (AD-SEMF). Thanks to the large hyperfine coupling constant (A = 38 mT), a characteristic negative MFE on the radical yield was observed at a magnetic field lower than 60 mT whereas a positive effect due to the conventional hyperfine (HFM) and relaxation mechanisms (RM) was observed at higher magnetic field. The negative effect can be assigned to the mechanism "so-called" low field effect (LFE) mechanism and has been analyzed thoroughly using a model calculation incorporating a fast spin dephasing process. The time scale of the spin mixing process of LFE studied by AD-SEMF is shorter than the lifetime of the recombination kinetics of the radical pair. These results indicate that the LFE originates from the coherent spin motion. This can be interfered from the fast spin dephasing caused by electron spin interaction fluctuations.
Collapse
Affiliation(s)
- Toshiaki Suzuki
- Department of Chemistry, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8571, Japan
| | | | | | | |
Collapse
|