New Possibilities for Magnetic Control of Chemical and Biochemical Reactions

Abstract

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 isotopeSi, enrichment of O 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 obs...

Retinoblastoma: Magnetic Isotope Effects Might Make a Difference in the Current Anti-Cancer Research Strategy

“…So occurring simultaneously with the sharp MIE-induced enzyme suppression, this fact itself makes it possible to consider these short, size-invalid, DNA segments not-fitting their crucial role in the DNA repair based protection of cancer cell. This confirms a concept (4,5,11,12) taking DNApolβ as a legitimate target for anti-tumor agents since its inhibition deprives the tumor cell of a DNA base-excision repair.…”

“…Recognizing the MIE phenomenon as a powerful modulator for matalloenzyme programmed phosphate transferring catalysis in vivo (10) and in vitro (11), it is hardly possible to underestimate its cytostatic potential as long as a MIE-DNApolβ match leads to a breakdown of the DNA repair related survival of neoplasma. Since physical and biophysical ion-radical mechanism of MIE is no longer enigmatic (2, 10, 11), we may disclose a fresh insight into not only the processes of replication and reparation of DNA but into some linked areas of molecular pharmacology as well.…”

Retinoblastoma Case: Shall we Get A Paramagnetic Trend in Chemotherapy?

“…Some prophetic predictions regarding a therapeutic validity of epigenic DNA expression control in retinoblastoma (RB) has been publicized lately [8] and then confirmed considering the cancer DNA repair machinery as a target once its key part, DNA Polymerase Beta, overexpressed [2,7]. However, being predominantly based on experiments with RB cell lines like WERI-RB or Y79, this statement still may be treated as "immature" since the in vivo operating neuro-immune and neuro-endocrine paths are no doubt capable of making an impact on intracellular epigenetic environment.…”

“…This itself is about to deprive the cell of its usual DNA repair capabilities [1,2,8] which is a reason to expect the tumor growth to get limited [3,9]. Thus, the MIE-dependent formation of these "size The applied medicinal significance of these data looks promising due to the followings: (a) the MIE ion-radical mode [4][5][6][7] does not allow the most members of DNA Polymerases diversity (α, γ, δ) to get operated this way since the electron transfer distances in their catalytic sites are too long to make a "magnet" manifesting its MIE [1,3,5]; while (b) DNApolB is a perfect target for MIE-ions considering this enzyme active site 3D-structure [4,7]. Besides, (c) the above specified "magnets" were proven of being the substantial subjects for a cancer targeted delivery conducted with the low-toxic amphiphilic nanocationites [5,11].…”

“…This also makes them legitimate targets for pharmacologically promising inhibitors [3] including paramagnetic (magnetic, in brief) bivalent metal ions, (nMe 2+ ) [4,5]. Being capable to promote the magnetic isotope effects (MIE) in vivo and in vitro these ions could be employed to "turn off" DNApolB to limit the tumor growth [6,7]. Particularly, retinoblastoma (RB) is an appropriate object for such an impact due to the DNA repair engaging paths of epigenetic control revealed in this peculiar cancer [8].…”