Nonmagnetic Isotopes Research Articles

Magnetic-Isotope Effects of Magnesium and Zinc in Enzymatic ATP Hydrolysis Driven by Molecular Motors

The effects of different magnesium and zinc isotopes on the enzyme activity of myosin subfragment-1 have been explored. The rate of the enzymatic ATP hydrolysis in reaction media enriched with the magnetic isotope, 25Mg, is twice as high as it is in reaction media enriched with the nonmagnetic isotopes, 24Mg or 26Mg. A similar effect of nuclear spin catalysis has been detected in the experiments with zinc isotopes as cofactors of the enzyme. The rate of the enzymatic ATP hydrolysis with magnetic 67Zn increases by 40–50% compared to that with nonmagnetic 64Zn or 68Zn. The magnetic-isotope effects have been observed at the physiological concentration of magnesium and zinc chlorides (5 mM). The catalytic effect of the magnetic magnesium isotope 25Mg has been revealed in the experiments with Mg-dependent ATPase of myometrial plasma membranes. The magnetic-isotope effects indicate that there is a spin-selective rate-limiting step in the chemo-mechanical process driven by the “molecular motor” due to the energy of ATP hydrolysis and that nuclear spin catalysis causes acceleration of this stage. Some possible mechanisms of the nuclear spin catalysis are discussed.

Effect of Magnesium Isotopes on Antibiotic Sensitivity of E. coli

The effect of 25Mg, a magnetic magnesium isotope, on the sensitivity of Escherichia coli K12 TG1 to quinolone/fluoroquinolone (nalidixic acid and ciprofloxacin) and aminoglycoside antibiotics (amikacin and tobramycin) was found. In the case of fluoroquinolones, determination of antibiotic sensitivity by the disc diffusion method revealed the 7‒14% larger growth inhibition zones on the medium with the magnetic magnesium isotope than for the same antibiotics in the variants with 24Mg, 26Mg, or the natural Mg isotope. The effect of the magnetic magnesium isotope 25Mg on the increase in resistance to the quinolones/fluoroquinolones group of antibiotics was observed independently of the determining method: the growth rate of E. coli culture incubated in the medium with 25Mg and ciprofloxacin decreased by 80% compared to the control without antibiotics, while in the variants with 24Mg, 26Mg, and natural Mg the decrease did not exceed 50%. An increase in antibiotic resistance (opposite magnetic isotopic effect) was shown for amikacin, tobramycin, and clindamycin. In the variants with amikacin and clindamycin, the growth inhibition zones of bacteria enriched with 25Mg were 16‒17 and 17‒24% smaller, respectively. An increase in resistance to tobramycin (aminoglycosides) was observed for submerged E. coli cultures growing in the medium with 25Mg: at the antibiotic concentration two times lower than the MIC, the growth rate of E. coli was 86% of the control, while in the variants with nonmagnetic isotopes or natural magnesium it decreased by 40‒50%. The mechanisms of magnetic isotopic effects of 25Mg are discussed: its effect on the enzymatic activity of Mg-dependent enzymes involved in protection of the cells from the action of antibiotics.

The Magnetic Isotopes Effect of Magnesium 25Mg on the Physiological Properties of Bacteria E. coli

Magnetic isotope effects of magnesium 25Mg on antibiotic resistance and biofilm formation of bacteria E. coli were discovered. The increase in antibiotic resistance in the presence of the ion 25Mg2+ was registered for E. coli cells incubated with quinolones, indicating the inhibiting effect of the magnetic moments of nuclei 25Mg on deoxyribonucleic acid (DNA) synthesis. It was discovered that the process of biofilm formation by the bacteria E. coli is magnetosensitive. Magnetic magnesium isotope presence in nutrient media stimulated formation of biofilm compared with nonmagnetic isotopes 24, 26Mg. As e result the enrichment of media by magnetic magnesium can be used to control the physiological properties of bacteria: biofilm formation and antibiotic resistance.

Magnetic Isotopes of 25Mg and 67Zn and Magnetic Fields Influence on Adenosine Triphosphate Content in Escherichia Coli

Studies on the magnetic isotopes effect of zinc 67Zn and magnesium 25Mg on the adenosine triphosphate (ATP) concentration in living organisms were held in this work on the example of E. coli bacteria. External static magnetic fields 0-100 mT were used to enhance the effect of magnetic isotopes on intracellular processes. Enrichment of microorganisms with magnesium or zinc isotopes during growth changes the ATP concentration in cells depending on the type of isotope – magnetic or non-magnetic. The effect of weak magnetic fields of 0-10 mT stimulates the bacterial cell growth and the intracellular ATP concentration change. The maximum concentration of ATP was achieved by using a magnetic isotope of magnesium 25Mg and exposure of bacteria to the static magnetic fields 70-90 mT. Non-magnetic isotopes of magnesium or zinc and magnetic fields other than the ranges 0-10 and 70-90 mT can be used to decrease the rate of ATP synthesis.

Magnetic fields and magnetic isotope 25Mg effects on biofilms formation by bacteria E. coli

The biofilm formation by bacteria E. coli is a magnetosensitive process. The combined effects of a magnetic magnesium isotope 25Mg and a static magnetic field in the range of 20-35 mT stimulate biofilm formation by bacteria E. coli compared to non-magnetic magnesium isotopes 24,26Mg. Magnetic field effects in the range of 2-10 mT, registered for all bacteria regardless of magnesium-isotope enrichment of nutrient medium, indicate the sensitivity of intracellular processes to weak magnetic fields.

Magnetic Fields and Magnetic Isotope 25Mg Effects on Biofilms Formation by Bacteria E. coli.

The biofilm formation by bacteria E. coli is a magnetosensitive process. The combined effects of a magnetic magnesium isotope 25Mg and a static magnetic field in the range of 20-35 mT stimulate biofilm formation by E. coli compared to nonmagnetic magnesium isotopes 24.26Mg. Magnetic field effects in the range of 2-10 mT, recorded for all bacteria regardless of the magnesium-isotope enrichment of the nutrient medium, indicate the sensitivity of intracellular processes to weak magnetic fields.

Biological effects of static magnetic fields and zinc isotopes on E. coli bacteria.

The sensitivity of intracellular enzymatic systems to static magnetic fields (SMFs) and magnetic isotopes has been shown both in vitro and in vivo. These effects are determined by the spin-dependent magnetosensitive stages of enzymatic reactions. The search for experimental evidence of the combined effect of SMFs and zinc magnetic isotope 67 Zn on the intracellular processes on Escherichia coliEscherichia coli bacteria has taken place in vivo. The joint effects of external SMFs and magnetic zinc isotope 67 Zn on vital functions of E.coli bacteria have been shown experimentally. The combined effect of isotope 67 Zn and weak SMFs (25-35 mT) causes a 2-4-fold increase in the colony-forming ability and growth rate constants of bacteria E. coli compared with nonmagnetic zinc isotopes 64,66 Zn. The effects of SMFs in the range of 2.2-8 mT were detected for all bacteria, regardless of zinc isotope content in the media. An increase in ATP concentration in E. coli was detected for bacteria grown on a medium with the magnetic isotope 67 Zn in the SMF range of 2.2-4.2 mT. The major elements' (Na, K, Ca, Mg, P, Zn) metabolism in E. coli depend on the intensity of SMFs and zinc isotopes. These data confirm the existence of intracellular enzymatic processes stages that are sensitive to SMFs and magnetic moments of atomic nuclei. It is important to note that magnetic zinc 67 Zn and magnesium 25 Mg isotopes induce effects on viability of E. coli in different SMF ranges. Bioelectromagnetics. 40:62-73, 2019. © 2018 Wiley Periodicals, Inc.

Mercury Isotopes in Earth and Environmental Chemistry

In Earth and environmental chemistry magnetic isotopes are the universal means to identify reaction mechanisms. Mass-independent fractionation of isotopes as a signature of mechanism occurs by two ways: first, via magnetic isotope effect (MIE), which is controlled by magnetic, or hyperfine, coupling between unpaired electrons and magnetic nuclei in paramagnetic species (in radicals, particularly), and, second, via nuclear volume effect (NVE), which is induced by the difference in volumes of isotopic nuclei. MIE is the dependence of the reaction rates on the nuclear magnetic moment of reactants and fractionates magnetic and nonmagnetic isotopes; NVE fractionates isotopes with different nuclear volumes. Both effects, MIE and NVE, are supposed to coexist in condensed phases. Decisive test for their differentiation is illustrated by example of radical pairs with mercury nuclei: if isotope fractionation is controlled by MIE, the ratio Δ201Hg/Δ199Hg is expected to be in the limits 1.05–1.25 for isotopic enrichment and 0.80–0.92 for impoverishment. If isotope fractionation is controlled by NVE, this ratio is estimated to be in the range 0.50–0.62. In contrast to MIE-induced two-directional fractionation, which is controlled by direction of coherent spin conversion of radical pair (triplet–singlet or vice versa), the NVE induces one-directional, universal isotope fractionation, almost independent on the reaction mechanism.

Firefly Luciferase Bioluminescence as a Tool for Searching Magnetic Isotope Effects in ATP-Dependent Enzyme Reactions

Cells and tissues are composed from atoms of chemical elements, some of which have two kinds of stable isotopes, magnetic and nonmagnetic ones. Not long ago, magnetic isotope effects (MIEs) have been discovered in experiments with cells enriched with magnetic or nonmagnetic isotopes of magnesium. These MIEs can stem from higher efficiency of the enzymes of bioenergetics in the cells enriched with magnetic magnesium isotope. In the studies of MIEs in biological systems, it is needed to monitor the ATP concentrations as the major energy source in cells. The most sensitive and rapid method of the ATP measurements is based on the use of the firefly luciferase–luciferin system. Since luciferase is the ATP-dependent enzyme and activated by Mg-ions, it is necessary to elucidate whether this enzyme is sensitive to magnetic field of the magnesium isotope’s nuclear spin. Herein we present the results of studying the effects of different isotopes of magnesium, magnetic 25Mg and nonmagnetic 24Mg and 26Mg, on bioluminescence spectra and enzymatic activity of firefly luciferase. It was shown, that neither kinetics of the bioluminescence signal nor the bioluminescence spectra manifest any statistically significant dependence on the type of magnesium isotope. So, no MIEs have been revealed in the luciferase-catalyzed oxidation of luciferin. It means that firefly luciferase bioluminescence can serve as the tool for search and studies of magnetic isotope effects in ATP-dependent enzyme reactions in biological systems, including the enzymatic synthesis and hydrolysis of ATP.

Magnetosensitivity of E. coli Bacteria in the Presence of Zinc Isotopes.

The combined effect of the zinc magnetic isotope 67Zn and weak magnetic field 25-35 mT causes a 2-4-fold increase in the colony-forming ability of bacteria E. coli in comparison with the nonmagnetic isotopes 64, 66Zn. The effects of magnetic field in the range of 2.2-8 mT were detected for all bacteria regardless of the zinc-isotope enrichment of the media. This indicates the sensitivity of intracellular processes to weak magnetic fields. An increase in the ATP concentration in E. coli cells was only detected for the bacteria grown on the medium with the magnetic zinc isotope in the range of 2.2-4.2 mT. The obtained data confirm the existence of stages of intracellular enzymatic processes that are sensitive to magnetic fields and magnetic moments of atomic nuclei.

Isotope effects on the spin dynamics of single-molecule magnets probed using muon spin spectroscopy.

Muon spin relaxation (μSR) experiments on a single-molecule magnet enriched in different Dy isotopes detect unambiguously the slowing down of the zero field spin dynamics for the non-magnetic isotope. This occurs in the low temperature regime dominated by quantum tunnelling, in agreement with previous ac susceptibility investigations. In contrast to the latter, however, μSR is sensitive to all fluctuation modes affecting the lifetime of the spin levels.

The Influence of Low Magnetic Fields and Magnesium Isotopes on E. coli Bacteria

The combined effects of external low static magnetic fields at 0–22 mT and magnesium isotopes on the growth and development of E. coli bacteria has been studied. The magnetic field and 25Mg magnetic isotope effects were obtained in two ranges: 0.8–3.0 and 8–13 mT. The experimental values of the growth rate, the number of CFUs and the ATP pool of bacteria enriched in magnetic magnesium isotope 25Mg (nuclear spin, I = 5/2) in the range of 0.8–3.0 mT are significantly higher compared to bacteria enriched in nonmagnetic isotopes 24Mg, 26Mg, or natural magnesium. The increase in the growth rate, colony-forming ability, and intracellular ATP concentration in bacteria in all groups cultivated under exposure to an external static magnetic field in the range of 0.8 to 3.0 mT confirms the existence of magnetosensitive stages of enzymatic reactions that proceed via the ion-radical mechanism. The combined influence of the magnetic field in the range of 8 to 13 mT and the magnesium magnetic isotope 25Mg on the colony forming ability of E. coli bacteria is associated with processes that are responsible for cell division. The above-mentioned effects of bacterial magnetosensitivity (to magnetic fields and magnetic isotopes) are in good agreement with theoretical predictions of the theory of spin-dependent enzymatic reactions.

Magnetosensitivity of bacteria E. coli: Magnetic isotope and magnetic field effects.

The biological effects of a 25 Mg nuclear spin and weak magnetic fields have been found and studied by using bacterial cells of Escherichia coli (E. coli) grown on standard M9 nutrient media with different isotopes of magnesium: 24 Mg, 25 Mg, 26 Mg, and a natural mixture of Mg isotopes. Among these isotopes only 25 Mg has a nuclear spin I = 5/2 and nuclear magnetic moment which have been known to affect enzymatic processes in vitro due to hyperfine interactions with uncoupled electrons of substrates. Other non-magnetic magnesium isotopes, 24 Mg and 26 Mg, have neither a nuclear spin (I = 0) nor a nuclear magnetic moment. Bacterial cells grown on 25 Mg-media and enriched with this isotope manifest a higher growth rate and colony-forming units (CFU) compared with cells grown on media containing nonmagnetic 24 Mg and 26 Mg isotopes. Magnetic field dependencies of CFU cells enriched with different magnesium isotopes have been obtained. The observed isotope-dependent differences are explained by intracellular enzymatic ion-radical reactions which are magnetic field and nuclear spin sensitive. Enzymatic synthesis of ATP is considered as the most probable magnetosensitive biochemical process in vivo as far as effectiveness of ATP production is concerned; it determines the viability of cells and was shown in vitro as a nuclear spin-dependent reaction. Bioelectromagnetics. 38:581-591, 2017. © 2017 Wiley Periodicals, Inc.

20 - Magnetic-Isotope Effects in ATP Hydrolysis Driven by Myosin as Evidence for a Free-Radical Intermediate in the Reaction

Some chemical elements have magnetic and nonmagnetic stable isotopes. The question arises if the magnetic fields of the atomic nuclei impact on efficiency of biocatalysts. Magnesium cation, Mg 2+ , serves as cofactor of ATP hydrolysis catalyzed by muscle myosin. Among three stable isotopes, 24 Mg, 25 Mg, 26 Mg with natural abundance 76.7, 10.13, 11.17 %, only 25 Mg is magnetic (nuclear spin I = 5/2) while 24 Mg and 26 Mg are nonmagnetic (I = 0). The effects of different isotopes of Mg on ATPase activity of isolated myosin were studied. It was found that the rate of the enzymatic ATP hydrolysis with 25 Mg is 2.0–2.5 times higher as compared to the nonmagnetic 24 Mg or 26 Mg. The magnetic isotope effect (MIE) was observed at physiological concentrations, 5 mM, of MgCl 2 . The similar MIE was found with zinc. Among five stable isotopes, 64 Zn, 66 Zn, 67 Zn, 68 Zn, and 70 Zn with natural abundance 48.6, 27.9, 4.1, 18.8, and 0.6 %, only 67 Zn is magnetic (I = 5/2). While Zn 2+ performs the cofactor function less efficiently than Mg 2+ , it was found that the rate of the enzymatic ATP hydrolysis with 67 Zn is 40-50 % higher as compared to the nonmagnetic 64 Zn or 68 Zn. On its own, MIE unambiguously testifies presence of a spin-selective rate-limiting step as the “bottle-neck” that is accelerated by the magnetic field of nuclear spin of 25 Mg or 67 Zn. In free-radical chemistry, MIE is the sufficient demonstration of a free-radical or radical ion pair as intermediate in the reaction under study (Buchachenko, 2013). One can assume that, under the condition of the electron-conformational excitation, there is a transfer of electron density from NH 2 group of Glu459 or OH– group of the bound water molecule to ADP3– or Mg 2+ / Zn 2+ in the active site of the enzyme with formation of the corresponding radical ion pair. Although detailed mechanisms of ability of myosin to perceive the nuclear magnetism require further investigations, the nuclear spin catalysis opens novel ways in free-radical biomedicine based on the stable magnetic isotopes. Supported by RFBR, project no. 14-04-00593.

Nuclear spin catalysis in living nature

Experiments with cells enriched in stable magnesium isotopes, magnetic 25Mg or nonmagnetic 24Mg and 26Mg, are carried out. It is revealed that adaptation of bacteria E. coli to the growth media enriched in magnetic 25Mg proceeds faster as compared to the growth media enriched in nonmagnetic magnesium isotopes. In experiments with another commonly accepted cell model, S. cerevisiae yeast, it is revealed that the rate constant of postradiation recovery of the cells after UV irradiation is two times higher for cells enriched in 25Mg than for cells enriched in the nonmagnetic isotope. In collaboration with Ukrainian colleagues from the Palladin Institute of Biochemistry, the effects of different isotopes of magnesium on ATPase activity of myosin isolated from myometrium are studied. It is found that the rate of the enzymatic hydrolysis of ATP for 25Mg is 2.0–2.5 times higher as compared to nonmagnetic isotopes 24Mg and 26Mg. Some possible mechanisms of magnetic isotope effects (nuclear spin catalysis) in biological objects are discussed.

Magnetic isotope of magnesium accelerates ATP hydrolysis catalyzed by myosin

In this paper, we present the results of experimental studies on the influence of different magnesium isotopes, magnetic 25Mg and nonmagnetic 24Mg or 26Mg, on ATP-hydrolytic activity of the isolated myosin subfragment-1. The reaction rate in the presence of magnetic 25Mg isotope turned out to be 2.0–2.5 times higher than that using non-magnetic 24Mg or 26Mg isotopes. In absence of the enzyme, as at spontaneous ATP hydrolysis in aqueous solution, no magnetic isotope effect was observed. Thus, a significant catalytic effect of the magnetic 25Mg isotope (nuclear spin catalysis) was discovered in the enzymatic hydrolysis of ATP.

Electron Spin Coherence of Shallow Donors in Natural and Isotopically Enriched Germanium.

Germanium is a widely used material for electronic and optoelectronic devices and recently it has become an important material for spintronics and quantum computing applications. Donor spins in silicon have been shown to support very long coherence times (T_{2}) when the host material is isotopically enriched to remove any magnetic nuclei. Germanium also has nonmagnetic isotopes so it is expected to support long T_{2}'s while offering some new properties. Compared to Si, Ge has a strong spin-orbit coupling, large electron wave function, high mobility, and highly anisotropic conduction band valleys which will all give rise to new physics. In this Letter, the first pulsed electron spin resonance measurements of T_{2} and the spin-lattice relaxation (T_{1}) times for ^{75}As and ^{31}P donors in natural and isotopically enriched germanium are presented. We compare samples with various levels of isotopic enrichment and find that spectral diffusion due to ^{73}Ge nuclear spins limits the coherence in samples with significant amounts of ^{73}Ge. For the most highly enriched samples, we find that T_{1} limits T_{2} to T_{2}=2T_{1}. We report an anisotropy in T_{1} and the ensemble linewidths for magnetic fields oriented along different crystal axes but do not resolve any angular dependence to the spectral-diffusion-limited T_{2} in samples with ^{73}Ge.

Stable magnetic isotopes: from spin chemistry to biomedicine

Biomolecular nanoreactors, like other cell structures, are composed of atoms of chemical elements many of which have magnetic and non-magnetic stable isotopes. The so-called magnetic isotope effect well known in spin chemistry is a direct consequence of the law of conservation of the electron angular moment (spin) and manifests itself in the fact that chemical reactions with participation of free radical pairs or ion-radical pairs exhibit different reaction rates and different yields of products according to whether the reactants contain magnetic or nonmagnetic isotopes. The magnetic isotope effects in the enzymatic catalysis were first discovered in the pioneering works of Russian scientists, A. L. Buchachenko and his co-workers. Our team studied living cells enriched in different isotopes of magnesium and discovered for the first time the magnetic isotope effects (nuclear spin catalysis) in vivo. The magnetic isotope 25Mg was much more efficient than the non-magnetic isotope 24Mg in stimulating the recovery processes of the S. cerevisiae yeast cells after short-wavelength UV irradiation. The E. coli bacterial cells are adapted substantially faster to a new growth medium containing magnetic 25Mg than to a medium containing non-magnetic 24Mg or 26Mg. Furthermore, the effects of magnesium isotopes on the muscle protein myosin were investigated in cooperation with Ukrainian biochemists and stimulation of the ATPase activity of the enzyme by the magnetic 25Mg isotope 2–2.5 times exceeding the enzyme activity in the presence of non-magnetic magnesium isotopes was detected. Detailed physicochemical mechanisms of the magnetic isotope effects in the enzymatic catalysis and elucidation of the biological mechanisms of enhancement of these effects in living cells are the objectives of further research. Nevertheless, the experimental results obtained to date provide grounds for believing that pharmaceutical agents enriched in 25Mg and possibly in the magnetic isotopes of some other chemical elements will find use in biomedicine, for example, in cardiology for prevention and treatment of acute hypoxia, in oncology as cytostatics, and for the development of new antistress agents and radiation protectors.

The magnetic isotope effect as a tool for apoptosis modulation in leukemic cells

Lymphocytes from healthy donors and leukemic cells of patients with acute B-lymphoblastic leukemia (BALL-1) and acute myeloid leukemia were exposed to nanoparticles bearing magnetic (Zn-67) and nonmagnetic (total isotope pool) nuclei of zinc. The values of the corresponding magnetic isotope effects determined as the ratio of LD50 magnitudes of preparations with magnetic and nonmagnetic zinc isotopes were 0, 3.5, and 1.5. Morphological studies using confocal and fluorescence microscopy showed apoptotic death of cells with the preparations; as well, there was an increase in the cell aggregation and better aggregation of nanoparticles in the case of 67Zn-NP, which resulted in a decrease of cytotoxicity. However the magnetic isotope effect was observed even in the case of aggregation.

Magnetic field effects in bacteria E. coli in the presence of Mg isotopes

The combined effect of weak magnetic fields and nuclear spins of the magnetic isotope 25Mg on the vital functions of E. coli bacterial cells was proved experimentally. For static external magnetic fields (0–15 mT), the value of colony-forming units of the bacteria enriched in the magnetic isotope 25Mg is higher than those for the bacterial cells containing nonmagnetic isotopes 24Mg and 26Mg and natural magnesium *Mg. According to the intracellular elemental composition, the content of the most important macro- and microelements depends on the type of the magnesium isotope (magnetic/nonmagnetic) and the external magnetic field. The magnetic field and magnetic isotope effects observed in bacteria E. coli prove the existence of magnetosensitive stages of enzymatic processes in living organisms.