Sensitive fluorescence-based detection of magnetic field effects in photoreactions of flavins (original) (raw)
Related papers
Time-resolved optical absorption microspectroscopy of magnetic field sensitive flavin photochemistry
The Review of scientific instruments, 2018
The photochemical reactions of blue-light receptor proteins have received much attention due to their very important biological functions. In addition, there is also growing evidence that the one particular class of such proteins, the cryptochromes, may be associated with not only a biological photo-response but also a magneto-response, which may be responsible for the mechanism by which many animals can respond to the weak geomagnetic field. Therefore, there is an important scientific question over whether it is possible to directly observe such photochemical processes, and indeed the effects of weak magnetic fields thereon, taking place both in purified protein samples in vitro and in actual biochemical cells and tissues. For the former samples, the key lies in being able to make sensitive spectroscopic measurements on very small volumes of samples at potentially low protein concentrations, while the latter requires, in addition, spatially resolved measurements on length scales sm...
Biological sensing of small field differences by magnetically sensitive chemical reactions
Nature
There is evidence that animals can detect small changes in the Earth's magnetic field by two distinct mechanisms, one using the mineral magnetite as the primary sensor and one using magnetically sensitive chemical reactions 1-14 . Magnetite responds by physically twisting 2,15 , or even reorienting the whole organism in the case of some bacteria 16 , but the magnetic dipoles of individual molecules are too small to respond in the same way. Here we assess whether reactions whose rates are affected by the orientation of reactants in magnetic fields could form the basis of a biological compass. We use a general model, incorporating biological components and design criteria, to calculate realistic constraints for such a compass. This model compares a chemical signal produced owing to magnetic field effects with stochastic noise and with changes due to physiological temperature variation 17 . Our analysis shows that a chemically based biological compass is feasible with its size, for any given detection limit, being dependent on the magnetic sensitivity of the rate constant of the chemical reaction.
No evidence for detectable direct effects of magnetic field on cellular autofluorescence
bioRxiv (Cold Spring Harbor Laboratory), 2022
Dramatically increased levels of electromagnetic radiation in the environment have raised concerns over the potential health hazards of electromagnetic fields. Various biological effects of magnetic fields have been proposed. Despite decades of intensive research, the molecular mechanisms procuring cellular responses remain largely unknown. The current literature is conflicting with regards to evidence that magnetic fields affect functionality directly at cellular level. Therefore, a search for potential direct cellular effects of magnetic fields represents a cornerstone that may propose an explanation for potential health hazards associated with magnetic fields. Recently, it was postulated that autofluorescence of HeLa cells is magnetic field sensitive, relying on single-cell imaging kinetic measurements. Here, we explore the utility of this approach by undertaking a screen for magnetic sensitivity of cellular autofluorescence in statistically relevant numbers (90-107) of HeLa cells. We did not observe any changes in cellular autofluorescence decay, when a modulated magnetic field was applied. We present a number of arguments indicating weak points in the analysis of magnetic field effects based on the imaging of cellular autofluorescence decay. Our work indicates that new methods are required to elucidate the effects of magnetic fields at the cellular level.
Solvent effect on magnetic field modulation of excbplex fluorescence in polar solutions
Chemical Physics Letters, 1981
The magnetic field effect on pyrenefN,Nðylamline steady-state exciplex fluorescence was found to depend on solvent polarity. It is explained in terms of a model based on macroscopic properties of the system. Potential barriers between radical ion pair state and fluorescent exciplex, E, = 0.18-0.23 eV at room temperature, have been obtained from comparison of
Magnetic field modulation of receptor binding
Magnetic Resonance in Medicine, 1989
Although it is widely held that the magnetic fields encountered during magnetic resonance imaging (MRI) and other procedures have no discernible effect on biological systems, we find that at early times of incubation, the amount of binding ofthe neurotoxin, a-bungarotoxin, to nicotinic acetylcholine receptor is significantly reduced in a constant 2.0-T magnetic field. This finding suggests that steady magnetic fields can directly affect the functional activity of biologically important macromolecules, in this particular case a neurotransmitter receptor. o 1989 Academic press, Inc.
Photoresponsive magnetization reversal in green fluorescent protein chromophore based diradicals
Journal of Photochemistry and …, 2011
We present density functional theory based calculations on six diradicals in which imino nitroxide (IN) and IN or oxo-or phospha-verdazyl radical centres are linked by fragments of structures called cyan, blue and green fluorescent protein, respectively. In the latter two variants the indolyl fragment of cyan fluorescent protein (CFP) is replaced by phenyl and phenol moiety to obtain blue fluorescent protein Y66F GFP (BFPF) and green fluorescent protein (GFP). The photoinduced cis-trans isomerization of these diradical substituted chromophores is accompanied by changes from antiferro-to ferro-magnetic spin coupling on the radical centres. The calculations in this work provide predictions of the change of magnetic response to photo excitation. The estimated magnetic exchange coupling constants associated with cis-trans isomerization of the chromophores can be useful parameters in designing radical substituted isomeric fluorescent chromophores. Upon irradiation with light of appropriate wavelength, the dark trans diradicals turn into their fluorescent cis isomers. Therefore, photoinduced magnetic crossover from antiferromagnetic to ferromagnetic regime associated with the change in color would be noticed in all three cases. This is a novel observation in case of the systems with GFP chromophore and its variants. These diradicals are potentially very useful in different applications and biocompatibility of such systems makes them prospective in different in vivo treatments. Moreover, change in color associated with magnetic crossover for these diradicals increases their suitability as biological taggers.
Biochimica Et Biophysica Acta - Biomembranes, 1979
Spin probes differing in the position of their paramagnetic centre are used to quench the fluorescence of pyrene derivatives and chlorophylls incorporated into dimyristoyl phosphatidylcholine membranes. Pyrene butyric acid and pyrene decanoic acid with known orientation relative to the membrane surface are investigated. The quenching efficiency of fatty acid spin probes is dependent on the position of the nitroxide radical group in the fatty acid chain. Using this short range interaction we developed a spectroscopic method to characterize the molecular arrangement within the lipid membrane. Applied to chlorophyll-containing vesicles, we were able to characterize the orientation of the porphyrin ring within the membrane. Moreover, the chlorophyll fluorescence is also quenched by a water.soluble spin label. Therefore the porphyrin ring appears to be orientated in the polar head group region of the lipid layer, but not to be protruding out into the water phase. This conclusion is confirmed by the use of pyrene derivatives. Fluorescence quenching by a water-soluble spin label within the lipid matrix is observed even in the rigid state of the membrane. Fluorescence lifetime measurements suggest the existence of two different quenching mechanisms: (1) a static quenching occurring below the lipid phase transition temperature, and (2) an additional dynamic quenching taking place in the fluid state of the lipid bilayer.
Magnetic-field effect on the photoactivation reaction of Escherichia coli DNA photolyase
Proceedings of The National Academy of Sciences, 2008
One of the two principal hypotheses put forward to explain the primary magnetoreception event underlying the magnetic compass sense of migratory birds is based on a magnetically sensitive chemical reaction. It has been proposed that a spin-correlated radical pair is produced photochemically in a cryptochrome and that the rates and yields of the subsequent chemical reactions depend on the orientation of the protein in the Earth's magnetic field. The suitability of cryptochrome for this purpose has been argued, in part, by analogy with DNA photolyase, although no effects of applied magnetic fields have yet been reported for any member of the cryptochrome/photolyase family. Here, we demonstrate a magnetic-field effect on the photochemical yield of a flavin-tryptophan radical pair in Escherichia coli photolyase. This result provides a proof of principle that photolyases, and most likely by extension also cryptochromes, have the fundamental properties needed to form the basis of a magnetic compass.
Scientific Reports, 2023
Dramatically increased levels of electromagnetic radiation in the environment have raised concerns over the potential health hazards of electromagnetic fields. Various biological effects of magnetic fields have been proposed. Despite decades of intensive research, the molecular mechanisms procuring cellular responses remain largely unknown. The current literature is conflicting with regards to evidence that magnetic fields affect functionality directly at the cellular level. Therefore, a search for potential direct cellular effects of magnetic fields represents a cornerstone that may propose an explanation for potential health hazards associated with magnetic fields. It has been proposed that autofluorescence of HeLa cells is magnetic field sensitive, relying on single-cell imaging kinetic measurements. Here, we investigate the magnetic field sensitivity of an endogenous autofluorescence in HeLa cells. Under the experimental conditions used, magnetic field sensitivity of an endogenous autofluorescence was not observed in HeLa cells. We present a number of arguments indicating why this is the case in the analysis of magnetic field effects based on the imaging of cellular autofluorescence decay. Our work indicates that new methods are required to elucidate the effects of magnetic fields at the cellular level. Despite decades of research, the biological effects of magnetic fields still remain a highly debatable topic without consensus over major outcomes 1-4. Thus far, dozens of studies have ascribed a variety of biological effects to both electromagnetic as well as static magnetic fields 5-8. It has been widely acknowledged that many investigations which deal with the biological impact of magnetic fields are hampered by shortcomings in experimental design and often also by the lack of reproducibility 1-4,6,7,9,10. Specifically, direct attempts to replicate key findings on biological effects of magnetic fields have been largely unsuccessful 11-15. Therefore, the jury is still out with regards to the molecular and/or biophysical foundations for these proposed cellular effects. Considering all the abovementioned queries, studies focusing on biological effects of magnetic fields are intriguing, challenging, and timely. Furthermore, some epidemiological studies presumed a low interrelation between residential proximity to high-voltage power lines and childhood leukemia 16-18. Recent literature analysis showed that the majority of large-scale epidemiological studies do not support this association (for review see 19 and references therein). In this flow of data the International Agency for Research on Cancer (IARC) classified magnetic fields of extremely low-frequencies as "possibly carcinogenic to humans" (Group 2B) in 2002, admitting that the evidence is limited 20. Recent systematic reviews on bioeffects of weak and intermediate, static, and different frequency range, magnetic and electromagnetic fields found, that current evidence does not allow one to draw a firm conclusion for biological and health-related consequences of exposure to those fields 4,21,22. Numerous studies on biological effects of magnetic fields have produced many hypothesizes, proposing distinct potential mechanisms of magnetic field action on biological matter 1-3,6-8. One hypothesis explaining