Magnetic field and nuclear spin influence on the DNA synthesis rate.

The rate of a chemical reaction can be sensitive to the isotope composition of the reactants, which provides also for the sensitivity of such "spin-sensitive" reactions to the external magnetic field. Here we demonstrate the effect of the external magnetic field on the enzymatic DNA synthesis together with the effect of the spin-bearing magnesium ions ([Formula: see text]Mg). The rate of DNA synthesis monotonously decreased with the external magnetic field induction increasing in presence of zero-spin magnesium ions ([Formula: see text]Mg). On the contrary, in the presence of the spin-bearing magnesium ions, the dependence of the reaction rate on the magnetic field induction was non-monotonous and possess a distinct minimum at 80-100 mT. To describe the observed effect, we suggested a chemical scheme and biophysical mechanism considering a competition between Zeeman and Fermi interactions in the external magnetic field.

Isotope Effects Induced by Molecular Compression.

Zero-point energies (ZPEs) of hydroxyl ion and hydrogen and water molecules, free and compressed in C60 cages, are computed; the excess energy acquired by molecules under compression is in the range 2-3 kcal/mol and depends on the isotopes. The differences in ZPE of compressed isotopic molecules strongly exceed those of the free molecules, resulting in the large deuterium and tritium isotope effects. These effects induced by compression are suggested as a probe for testing molecular compression of enzymatic sites; they may be important for understanding enormously large isotope effects observed in some enzymatic reactions, where they are attributed to the tunneling.

A specific role of magnetic isotopes in biological and ecological systems. Physics and biophysics beyond.

The great diversity of molecular processes in chemistry, physics, and biology exhibits universal property: they are controlled by powerful factor, angular momentum. Conservation of angular momentum (electron spin) is a fundamental and universal principle: all molecular processes are spin selective, they are allowed only for those spin states of reactants whose total spin is identical to that of products. Magnetic catalysis induced by magnetic interactions is a powerful and universal means to overcome spin prohibition and to control physical, chemical and biochemical processes. Contributing almost nothing in total energy, being negligibly small, magnetic interactions are the only ones which are able to change electron spin of reactants and switch over the processes between spin-allowed and spin-forbidden channels, controlling pathways and chemical reactivity in molecular processes. The main source of magnetic and electromagnetic effects in biological systems is now generally accepted and demonstrated in this paper to be radical pair mechanism which implies pairwise generation of radicals in biochemical reactions. This mechanism was convincingly established for enzymatic adenosine triphosphate (ATP) and desoxynucleic acid (DNA) synthesis by using catalyzing metal ions with magnetic nuclei (25Mg, 43Ca, 67Zn) and supported by magnetic field effects on these reactions. The mechanism, is shown to function in medicine as a medical remedy or technology (trans-cranial magnetic stimulation, nuclear magnetic control of the ATP synthesis in heart muscle, the killing of cancer cells by suppression of DNA synthesis). However, the majority of magnetic effects in biology remain to be irreproducible, contradictory, and enigmatic. Three sources of such a state are shown in this paper to be: the presence of paramagnetic metal ions as a component of enzymatic site or as an impurity in an uncontrollable amount; the property of the radical pair mechanism to function at a rather high concentration of catalyzing metal ions, when at least two ions enter into the catalytic site; and the kinetic restrictions, which imply compatibility of chemical and spin dynamics in radical pair. The purpose of the paper is to analyze the reliable sources of magnetic effects, to elucidate the reasons of their inconsistency, to show how and at what conditions magnetic effects exhibit themselves and how they may be controlled, switched on and off, taking into account not only biological and madical but some geophysical and environmental aspects as well.

Nuclear spin selectivity in enzymatic catalysis: A caution for applied biophysics.

Nuclear magnetic ions 25Mg2+, 43Ca2+, and 67Zn2+ suppress DNA synthesis by 3-5 times with respect to ions with nonmagnetic nuclei. This observation unambiguously evidences that the DNA synthesis occurs by radical pair mechanism, which is well known in chemistry and implies pairwise generation of radicals by electron transfer between reaction partners. This mechanism coexists with generally accepted nucleophilic one; it is switched on, when at least two ions enter into the catalytic site. It is induced by both sorts of ions, magnetic and nonmagnetic but it functions by 3-5 times more efficiently with magnetic ions stimulating radical pair mechanism. Decreasing catalytic activity of polymerases by 3-5 times, nuclear magnetic ions 25Mg2+, 43Ca2+, and 67Zn2+ even more strongly, by 30-50 times, increase mortality of cancer cells. The two reasons of this unique phenomenon are suggested: first, the high concentration of nuclear magnetic ions delivered by specific nano-container into the cancer cells, and, second, generation of short DNA fragments by polymerases loaded with nuclear magnetic ions, which is known to activate protein p53, efficiently stimulating apoptosis of cancer cells.

New Possibilities for Magnetic Control of Chemical and Biochemical Reactions.

Chemistry is controlled by Coulomb energy; magnetic energy is lower by many orders of magnitude and may be confidently ignored in the energy balance of chemical reactions. The situation becomes less clear, however, when reaction rates are considered. In this case, magnetic perturbations of nearly degenerate energy surface crossings may produce observable, and sometimes even dramatic, effects on reactions rates, product yields, and spectroscopic transitions. A case in point that has been studied for nearly five decades is electron spin-selective chemistry via the intermediacy of radical pairs. Magnetic fields, external (permanent or oscillating) and the internal magnetic fields of magnetic nuclei, have been shown to overcome electron spin selection rules for pairs of reactive paramagnetic intermediates, catalyzing or inhibiting chemical reaction pathways. The accelerating effects of magnetic stimulation may therefore be considered to be magnetic catalysis. This type of catalysis is most commonly observed for reactions of a relatively long-lived radical pair containing two weakly interacting electron spins formed by dissociation of molecules or by electron transfer. The pair may exist in singlet (total electron spin is zero) or triplet (total spin is unity) spin states. In virtually all cases, only the singlet state yields stable reaction products. Magnetic interactions with nuclear spins or applied fields may therefore affect the reactivity of radical pairs by changing the angular momentum of the pairs. Magnetic catalysis, first detected via its effect on spin state populations in nuclear and electron spin resonance, has been shown to function in a great variety of well-characterized reactions of organic free radicals. Considerably less well studied are examples suggesting that the basic mechanism may also explain magnetic effects that stimulate ATP synthesis, eliminating ATP deficiency in cardiac diseases, control cell proliferation, killing cancer cells, and control transcranial magnetic stimulation against cognitive deceases. Magnetic control has also been observed for some processes of importance in materials science and earth and environmental science and may play a role in animal navigation. In this Account, the radical pair mechanism is applied as a consistent explanation for several intriguing new magnetic phenomena. Specific examples include acceleration of solid state reactions of silicon by the magnetic isotope 29Si, enrichment of 17O during thermal decomposition of metal carbonates and magnetic effects on crystal plasticity. In each of these cases, the results are consistent with an initial one-electron transfer to generate a radical pair. Similar processes can account for mass-independent fractionation of isotopes of mercury, sulfur, germanium, tin, iron, and uranium in both naturally occurring samples and laboratory experiments. In the area of biochemistry, catalysis by magnetic isotopes has now been reported in several reactions of DNA and high energy phosphate. Possible medical applications of these observations are pointed out.

Why magnetic and electromagnetic effects in biology are irreproducible and contradictory?

The main source of magnetic and electromagnetic effects in biological systems is now generally accepted and demonstrated in this paper to be radical pair mechanism which implies pairwise generation of radicals in biochemical reactions. This mechanism was convincingly established for enzymatic adenosine triphosphate (ATP) and desoxynucleic acid (DNA) synthesis by using catalyzing metal ions with magnetic nuclei ((25)Mg, (43)Ca, (67)Zn) and supported by magnetic field effects on these reactions. The mechanism, is shown to function in medicine as a medical remedy or technology (trans-cranial magnetic stimulation, nuclear magnetic control of the ATP synthesis in heart muscle, the killing of cancer cells by suppression of DNA synthesis). However, the majority of magnetic effects in biology remain to be irreproducible, contradictory, and enigmatic. Three sources of such a state are shown in this paper to be: the presence of paramagnetic metal ions as a component of enzymatic site or as an impurity in an uncontrollable amount; the property of the radical pair mechanism to function at a rather high concentration of catalyzing metal ions, when at least two ions enter into the catalytic site; and the kinetic restrictions, which imply compatibility of chemical and spin dynamics in radical pair. It is important to keep in mind these factors to properly understand and predict magnetic effects in magneto-biology and biology itself and deliberately use them in medicine.

Magnetic isotope and magnetic field effects on the DNA synthesis.

Magnetic isotope and magnetic field effects on the rate of DNA synthesis catalysed by polymerases ß with isotopic ions (24)Mg(2+), (25)Mg(2+) and (26)Mg(2+) in the catalytic sites were detected. No difference in enzymatic activity was found between polymerases ß carrying (24)Mg(2+) and (26)Mg(2+) ions with spinless, non-magnetic nuclei (24)Mg and (26)Mg. However, (25)Mg(2+) ions with magnetic nucleus (25)Mg were shown to suppress enzymatic activity by two to three times with respect to the enzymatic activity of polymerases ß with (24)Mg(2+) and (26)Mg(2+) ions. Such an isotopic dependence directly indicates that in the DNA synthesis magnetic mass-independent isotope effect functions. Similar effect is exhibited by polymerases ß with Zn(2+) ions carrying magnetic (67)Zn and non-magnetic (64)Zn nuclei, respectively. A new, ion-radical mechanism of the DNA synthesis is suggested to explain these effects. Magnetic field dependence of the magnesium-catalysed DNA synthesis is in a perfect agreement with the proposed ion-radical mechanism. It is pointed out that the magnetic isotope and magnetic field effects may be used for medicinal purposes (trans-cranial magnetic treatment of cognitive deceases, cell proliferation, control of the cancer cells, etc).

Mass-independent isotope effects.

Three fundamental properties of atomic nuclei-mass, spin (and related magnetic moment), and volume-are the source of isotope effects. The mostly deserved and popular, with almost hundred-year history, is the mass-dependent isotope effect. The first mass-independent isotope effect which chemically discriminates isotopes by their nuclear spins and nuclear magnetic moments rather than by their masses was detected in 1976. It was named as the magnetic isotope effect because it is controlled by magnetic interaction, i.e., electron-nuclear hyperfine coupling in the paramagnetic species, the reaction intermediates. The effect follows from the universal physical property of chemical reactions to conserve angular momentum (spin) of electrons and nuclei. It is now detected for oxygen, silicon, sulfur, germanium, tin, mercury, magnesium, calcium, zinc, and uranium in a great variety of chemical and biochemical reactions including those of medical and ecological importance. Another mass-independent isotope effect was detected in 1983 as a deviation of isotopic distribution in reaction products from that which would be expected from the mass-dependent isotope effect. On the physical basis, it is in fact a mass-dependent effect, but it surprisingly results in isotope fractionation which is incompatible with that predicted by traditional mass-dependent effects. It is supposed to be a function of dynamic parameters of reaction and energy relaxation in excited states of products. The third, nuclear volume mass-independent isotope effect is detected in the high-resolution atomic and molecular spectra and in the extraction processes, but there are no unambiguous indications of its importance as an isotope fractionation factor in chemical reactions.

Photo-oxidation of water by molecular oxygen: isotope exchange and isotope effects.

Photolysis of (17,18)O-labeled water in the presence of molecular oxygen is accompanied by transfer of (17)O and (18)O isotopes from water to oxygen, demonstrating that photoinduced oxidation of water does occur. The reaction exhibits the following isotope effect: oxidation of H(2)(17)O is faster by 2.6% (in the Earth's magnetic field) and by 6.0% (in the field 0.5 T) than that of H(2)(18)O. The effect is supposed to arise in the two spin-selective, isotope-sorting reactions-recombination and disproportionation-in the pairs of encountering HO(2) radicals. The former is spin allowed from the singlet state; the latter occurs only in the triplet one. Nuclear spin sorting produced by these reactions proceeds in opposite directions with the dominating contribution of recombination, which provides observable (17)O/(18)O isotope fractionation in favor of magnetic isotope (17)O. Neither isotope exchange nor the reaction itself occurs in the dark.

Ion-radical mechanism of enzymatic ATP synthesis: DFT calculations and experimental control.

A new, ion-radical mechanism of enzymatic ATP synthesis was recently discovered by using magnesium isotopes. It functions at a high concentration of MgCl(2) and includes electron transfer from the Mg(H(2)O)(m)(2+)(ADP(3-)) complex (m = 0-4) to the Mg(H(2)O)(n)(2+) complex as a primary reaction of ATP synthesis in catalytic sites of ATP synthase and kinases. Here, the structures and electron transfer reaction energies of magnesium complexes related to ATP synthesis are calculated in terms of DFT. ADP is modeled by pyrophosphate anions, protonated (HP(2)O(7)H(2-), HP(2)O(7)CH(3)(2-)) and deprotonated (HP(2)O(7)(3-), CH(3)P(2)O(7)(3-)). The reaction generates an ion-radical pair, composed of Mg(H(2)O)(n)(+) ion and pyrophosphate anion-radical coordinated to Mg(2+) ion. The addition of the latter to the substrate P=O bond results in ATP formation. Populations of the singlet and triplet states and singlet-triplet spin conversion in the pair are controlled by hyperfine coupling of unpaired electrons with magnetic (25)Mg and (31)P nuclei and by Zeeman interaction. Due to these two interactions, the yield of ATP is a function of nuclear magnetic moment and magnetic field; both of these effects were experimentally detected. Electron transfer reaction does not depend on m but strongly depends on n. It is exoergic and energy allowed at 0 < or = n << infinity for the deprotonated pyrophosphate anions and at 0 < or = n < 4 for the protonated ones; for other values of n, the reaction is energy deficient and forbidden. The boundary between exoergic and endoergic regimes corresponds to the trigger magnitude n* (n* = 4 for protonated anions and 6 < n* << infinity for deprotonated ones). These results explain why ATP synthesis occurs only in special devices, molecular enzymatic machines, but not in water (n = infinity). Biomedical consequences of the ion-radical enzymatic ATP synthesis are also discussed.

The C60-fullerene porphyrin adducts for prevention of the doxorubicin-induced acute cardiotoxicity in rat myocardial cells.

This is a fullerene-based low toxic nanocationite designed for targeted delivery of the paramagnetic stable isotope of magnesium to the doxorubicin (DXR)-induced damaged heart muscle providing a prominent effect close to about 80% recovery of the tissue hypoxia symptoms in less than 24 hrs after a single injection (0.03 - 0.1 LD50). Magnesium magnetic isotope effect selectively stimulates the ATP formation in the oxygen-depleted cells due to a creatine kinase (CK) and mitochondrial respiratory chain-focusing "attack" of 25Mg2+ released by nanoparticles. These "smart nanoparticles" with membranotropic properties release the overactivating cations only in response to the intracellular acidosis. The resulting positive changes in the energy metabolism of heart cell may help to prevent local myocardial hypoxic (ischemic) disorders and, hence, to protect the heart muscle from a serious damage in a vast variety of the hypoxia-induced clinical situations including DXR side effects.

Magnetic field affects enzymatic ATP synthesis.

The rate of ATP synthesis by creatine kinase extracted from V. xanthia venom was shown to depend on the magnetic field. The yield of ATP produced by enzymes with 24Mg2+ and 26Mg2+ ions in catalytic sites increases by 7-8% at 55 mT and then decreases at 80 mT. For enzyme with 25Mg2+ ion in a catalytic site, the ATP yield increases by 50% and 70% in the fields 55 and 80 mT, respectively. In the Earth field the rate of ATP synthesis by enzyme, in which Mg2+ ion has magnetic nucleus 25Mg, is 2.5 times higher than that by enzymes, in which Mg2+ ion has nonmagnetic, spinless nuclei 24Mg or 26Mg. Both magnetic field effect and magnetic isotope effect demonstrate that the ATP synthesis is an ion-radical process, affected by Zeeman interaction and hyperfine coupling in the intermediate ion-radical pair.

Fullerene-based low toxic nanocationite particles (porphyrin adducts of cyclohexyl fullerene-C(60)) to treat hypoxia-induced mitochondrial dysfunction in mammalian heart muscle.

BACKGROUND: This is the first report on the targeted delivery of fullerene-based low toxic nanocationite particles (porphyrin adducts of cyclohexyl fullerene-C(60)) to treat hypoxia-induced mitochondrial dysfunction in mammalian heart muscle. METHODS: The magnetic isotope effect generated by the release of paramagnetic (25)Mg(2+) from these nanoparticles selectively stimulates the ATP overproduction in the oxygen-depleted cell. RESULTS: Because nanoparticles are membranotropic cationites, they will only release the overactivating paramagnetic cations in response to hypoxia-induced acidic shift. The resulting changes in the heart cell energy metabolism result in approximately 80% recovery of the affected myocardium in <24 h after a single injection (0.03-0.1 LD(50)). CONCLUSIONS: Pharmacokinetics and pharmacodynamics of the nanoparticles suggest their suitability for safe and efficient administration in either single or multi-injection (acute or chronic) therapeutic schemes for the prevention and treatment of clinical conditions involving myocardial hypoxia.

Magnesium isotope effects in enzymatic phosphorylation.

Recent discovery of magnesium isotope effect in the rate of enzymatic synthesis of adenosine triphosphate (ATP) offers a new insight into the mechanochemistry of enzymes as the molecular machines. The activity of phosphorylating enzymes (ATP-synthase, phosphocreatine, and phosphoglycerate kinases) in which Mg(2+) ion has a magnetic isotopic nucleus 25Mg was found to be 2-3 times higher than that of enzymes in which Mg(2+) ion has spinless, nonmagnetic isotopic nuclei 24Mg or 26Mg. This isotope effect demonstrates unambiguously that the ATP synthesis is a spin-dependent ion-radical process. The reaction schemes, suggested to explain the effect, imply a reversible electron transfer from the terminal phosphate anion of ADP to Mg(2+) ion as a first step, generating ion-radical pair with singlet and triplet spin states. The yields of ATP along the singlet and triplet channels are controlled by hyperfine coupling of unpaired electron in 25Mg+ ion with magnetic nucleus 25Mg. There is no difference in the ATP yield for enzymes with 24Mg and 26Mg; it gives evidence that in this reaction magnetic isotope effect (MIE) operates rather than classical, mass-dependent one. Similar effects have been also found for the pyruvate kinase. Magnetic field dependence of enzymatic phosphorylation is in agreement with suggested ion-radical mechanism.

Paramagnet enhanced nuclear relaxation of H2 in organic solvents and in H2@C60.

We have measured the bimolecular contribution (relaxivity) R1 (M(-1) s(-1)) to the spin-lattice relaxation rate for the protons of H2 and H2@C60 dissolved in organic solvents in the presence of paramagnet nitroxide radicals. It is found that the relaxation effect of the paramagnets is enhanced 5-fold in H2@C60 compared to H2 under the same conditions. 13C relaxivity in C60 induced by nitroxide has also been measured. The resulting value of R1 for 13C is substantially smaller relative to the 1H relaxation in H2@C60 than expected solely on the basis of the smaller magnetic moment of 13C. The observed values of R1 have been analyzed quantitatively using an outer-sphere model for bimolecular spin relaxation to extract an encounter distance, d, as the dependent variable. The resulting values of d for H2 and (13)C60 are similar to the sum of the van der Waals radii for the radical and the corresponding molecule. The value of d for (1)H2@C60 is substantially smaller than the corresponding van der Waals estimates, corresponding to larger than expected values of R1. A possible explanation for the enhanced relaxivity is a contribution from hyperfine coupling. Based on the results reported here, it seems that not only is the hydrogen molecule in H2@C60 not insulated from magnetic contact with the outside world but also the interaction with paramagnets is even stronger than expected based on distance alone.

Nuclear relaxation of H2 and H2@C60 in organic solvents.

The 1H nuclear spin-lattice relaxation time (T1) of H2 and H2@C60 in organic solvents varies with solvent, and it varies proportionally for H2 and for H2@C60. Since intermolecular magnetic interactions are ruled out, the solvent must influence the modulating processes of the relaxation mechanisms of H2 both in the solvent cage and inside C60. The temperature dependence of T1 also is very similar for H2 and H2@C60, T1 going through a maximum by varying the temperature in solvents which allow a wide range of temperatures to be explored. This behavior is attributed to the presence of dipolar and spin-rotation mechanisms which have an opposite dependence on temperature.

Magnetic isotope effect in the photolysis of organotin compounds.

Photolysis of organotin molecules RSnMe3 is shown to be a spin selective radical reaction accompanied by fractionation of magnetic, (117,119)Sn, and nonmagnetic, (118,120)Sn, isotopes between starting reagents and products. A primary photolysis process is a homolytic cleavage of the C-Sn bond and generation of a triplet radical pair as a spin-selective nanoreactor. Nuclear spin dependent triplet-singlet conversion of the pair results in the tin isotope fractionation. Experimentally detected isotope distribution unambiguously demonstrates that the classical, mass-dependent isotope effect is negligible in comparison with magnetic, spin-dependent isotope effect.