Ion-radical Mechanism Research Articles

ELECTROCHEMICAL BEHAVIOR OF DIMETHYLSULPHONE ON A PLATINUM ELECTRODE

In this work, we studied the effect of dimethylsulfone concentrations on the rate of anodic oxygen evolution and cathodic hydrogen evolution on a platinum electrode in acidic and alkaline media. By the method of calculating the DFT electron density functional at the level of the B97-3c theory using the Orca 4.2.0 program, the dimethyl sulfone bond breaking energy on the surface of platinum will be preferable through C-S bonds, according to the ion-radical mechanism. It has been confirmed by NMR and Raman spectroscopy that the end products of the anodic oxidation of dimethylsulfone in an acidic medium are methanesulfonic acid and dimethyldisulfone, in an alkaline medium - only dimethyldisulfone; the end products of cathodic reduction of DMSO2 are dimethylpolysulfides. Based on the obtained experimental results, a scheme of the electrocatalytic behavior of dimethylsulfone on a platinum electrode is proposed.

Photochemical Oxidation of Hexacyanoferrates in Aqueous Solutions

The main kinetic laws governing the photochemical degradation of stable cyanide compounds are studied using the example of hexacyanoferrates (HCFs) in the combined {Solar/S2O2−882−} oxidation system under the action of solar radiation. The efficient oxidation of intermediate products (toxic free cyanides) to nontoxic final products proceeds in the combined {Solar/S2O2−882−} system, in addition to the complete degradation of [Fe(CN)6]3− complex. The high efficiency of HCFs oxidation in the combined system is attributed to a conjugated ion-radical mechanism that includes (along with direct photolysis) oxidation with the participation of highly reactive oxygen species (ROSes)—reactive secondary oxidizing agents consisting mostly of hydroxyl radicals generated in situ during the simultaneous alkali and light activation of persulfate with solar radiation. The effect anions (chlorides, sulfates, bicarbonates) and associated organic pollutants (xanthates, phenol) most characteristic of cyanide-containing industrial wastewater have on HCF oxidation in the {Solar/S2O2−882−} system is studied. The studied anions promote HCF photochemical oxidation in a wide range of concentrations (1–10 mM).

Photooxidation based on UV/H2O2 process for arsenic removal from aqueous solutions

The main regularities of the photochemical oxidation of arsenic (III) were studied using a mercury-free UV source KrCl excilamp (222 nm). Comparative studies of the effectiveness of direct photolysis and combined oxidation of arsenic (III) in the presence of hydrogen peroxide were performed. It was found that the combined treatment of {UV / H2O2 } achieves a significant intensification of the oxidation process. The considered oxidizing systems according to the oxidation state of As (III) can be ranked according to {UV/H2O2 }>{H2O2 }>{UV}. The ion-radical mechanism of the photochemical oxidation of arsenic in the combined {UV / H2O2} oxidation system using the UV radiation of the KrCl excilamp is proposed. The fundamental possibility of using a mercury-free source of quasi-monochromatic radiation of the KrCl excilamp (222 nm) for the photochemical process based on the combined oxidation system {UV / H2O2} to remove arsenic from aqueous solutions is established.

Photocatalytic Oxidation of Thiocianates in Aqueous Solutions

The kinetic patterns of the photocatalytic oxidation of thiocyanates by persulfate under the influence of quasi-solar ultraviolet radiation (UV) were investigated. The influence of the main factors (pH, temperature of the reaction medium, nature of the catalyst, exposure time) on the efficiency of the oxidation of thiocyanates in the combined system {UV/S2O82–/Fe3+} was studied. It was established that the process of photocatalytic oxidation of thiocyanates proceeds via the ion-radical mechanism with the participation of reactive oxygen species generated in situ, mostly hydroxyl radicals and sulfate anion radicals.

ЭКСИЛАМПЫ КАК ПЕРСПЕКТИВНЫЙ ИСТОЧНИК УФ ИЗЛУЧЕНИЯ ДЛЯ ФОТОХИМИЧЕСКОГО ОБЕЗВРЕЖИВАНИЯ МЫШЬЯКСОДЕРЖАЩИХ ВОД

Актуальность исследования обусловлена необходимостью решения проблемы поступления в водные объекты токсичных веществ, в том числе соединений мышьяка, путем поиска и разработки эффективных фотохимических методов очистки и обезвреживания мышьяксодержащих растворов с использованием экологически чистых окислителей и современных безртутных источников УФ излучения. Цель: изучить возможности использования эксиламп для обезвреживания As-содержащих вод и установить закономерности фотохимической активации окисления мышьяка пероксидом водорода с использованием безртутного источника квазимонохроматического излучения KrCl-эксилампы. Объекты: модельные водные растворы мышьяка (III) с концентрацией 2,7 мкмоль∙л–1 (~0,2 мг/л), приготовленные на дистиллированной (УЭП=2 мкСм/см, рН 5,8) и водопроводной воде. Методы: спектрофотометрическое определение ионов мышьяка (III); контроль рН потенциометрическим методом, съемка электронных спектров поглощения растворов реагирующих веществ; поглощенная мощность излучения эксилампы, определенная методом химической актинометрии с атразином; оценка доз УФ излучения. Результаты. Установлена принципиальная возможность использования безртутного источника квазимонохроматического излучения KrCl-эксилампы (222 нм) для фотохимического окисления As(III) комбинированной системой {УФ/H2O2}. Изучены основные закономерности фотохимического окисления мышьяка (III) с использованием безртутного источника УФ излучения – KrCl-эксилампы (222 нм). Проведены сравнительные исследования эффективности прямого фотолиза и комбинированного окисления мышьяка (III) в водном растворе ультрафиолетовым излучением KrCl-эксилампы в присутствии пероксида водорода. По эффективности окисления As(III) рассмотренные окислительные системы можно выстроить в ряд: {УФ/H2O2}>{H2O2}>{УФ}. При комбинированной обработке {УФ/H2O2} наблюдается существенная интенсификация процесса окисления, через 10 минут остаточная концентрация мышьяка в растворе – ниже ПДК (0,01 мг/л). Также рассмотрено влияние гидрокарбонат-ионов, наиболее характерных анионов природных «водных матриц», на скорость реакции окисления As(III). Предложен ион-радикальный механизм фотохимического окисления мышьяка в комбинированной окислительной системе {УФ/H2O2} с использованием УФ излучения KrCl эксилампы.

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.

The investigation of liquid phase reaction of 4-aminotoluene with ozone in the presence of manganese bromide catalyst

A new catalytic system Mn(ІІ)- KBr-H 2 SO 4 -Ас 2 О to obtain 4-aminobenzaldehyde treatment by ozonation of 4-aminotoluene is developed. It has been shown that injection of potassium bromide significantly increases the depth, speed and selectivity of substrate oxidation, the main reaction product is 4-acetylaminobenzylidendiacetate with the discharge of 84.5%. Active particles responsible for the inclusion of 4-aminotoluene oxidation by a methyl group in the presence of manganese (II) acetate and potassium bromide is manganese bromide radical-ion (Mn (II) Br •), which is more active than Mn (III) and because of the higher rate of initiating oxidation by a methyl group. It is proposed the mechanism of the process by which the substrate oxidation is carried out by ion-radical unchain mechanism in which manganese-bromide radical is generated mainly in reaction with ozone. The main functions of sulfuric acid in the system are determined. It affects the main stages of the catalytic cycle: reduces the rate of manganese bromide complex reaction with ozone, significantly increases the rate of substrate oxidation by a methyl group and catalyzes the acylation reaction. These data are the basis for laying the foundations of technology of 4- aminotoluene oxidation by ozone to 4-aminobenzaldehyde and development of preparative and industrial methods for obtaining of aromatic aldehydes.

Mechanism of the initiation of low-temperature radiation telomerization of tetrafluoroethylene in hexafluoroisopropanol

ESR and IR spectroscopy and scanning calorimetry are used to investigate the mechanism of low-temperature radiation telomerization of tetrafluoroethylene (TFE) in hexafluoroisopropanol (HFIP). It is found that the low-temperature telomerization of TFE in HFIP proceeds via an ion-radical mechanism. This process is initiated by the radical anions (CF3)2C·-O− formed during the deprotonation of OH groups of primary hydroxyl radicals (CF3)2C·-OH exhibiting strong acidic properties. An interpretation of ESR spectra of irradiated HFIP recorded at 230–240 K is proposed with regard to the anisotropy on β-fluorine atoms and estimates of the angles between the corresponding C-F bonds and the axis of the unpaired electron orbital.

Magnetic Control of Enzymatic Phosphorylation

Ion-radical mechanism of the phosphorylation in the three processes of paramount importance – enzymatic ATP synthesis, DNA replication, and enzymatic phosphorylation of proteins, which are three cornerstones of the life chemistry, was discovered by using pure isotope forms of metal (magnesium, zinc, calcium) ions catalyzing enzymatic phosphorylation. It is convincingly proved by magnetic isotope and magnetic field effects on these processes. Ionradical mechanism is inevitable because on the pathway of compression of reactants in any molecular machine (enzyme) electron transfer occurs which precedes generally accepted nucleophilic reaction. Ion-radical mechanism being controlled by magnetic interactions is switched on when at least two metal ions enter in catalytic site: the first one is tightly bound with phosphate group, the second one is ‘free’, and not bound with phosphate groups; it acts as an electron acceptor, it is a main actor of the ion-radical mechanism. This mechanism may be also switched off by presence of Fe ions. Ion-radical mechanism manifests itself in the ATP synthesis in isolated mitochondria and in the whole living organisms as well in the widely used polymerase chain reaction of the DNA replication. The mechanism can be used to stimulate ATP synthesis and eliminate ATP deficiency at cardiac diseases, to control cell proliferation, to kill cancer cells, and control trans-cranial magnetic stimulation against cognitive deceases.

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 β with isotopic ions 24Mg2+, 25Mg2+ and 26Mg2+ in the catalytic sites were detected. No difference in enzymatic activity was found between polymerases β carrying 24Mg2+ and 26Mg2+ ions with spinless, non-magnetic nuclei 24Mg and 26Mg. However, 25Mg2+ ions with magnetic nucleus 25Mg were shown to suppress enzymatic activity by two to three times with respect to the enzymatic activity of polymerases β with 24Mg2+ and 26Mg2+ ions. Such an isotopic dependence directly indicates that in the DNA synthesis magnetic mass-independent isotope effect functions. Similar effect is exhibited by polymerases β with Zn2+ ions carrying magnetic 67Zn and non-magnetic 64Zn 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).

The Mitochondria Free Iron Content to Limit an Isotope Effect of 25Mg2+ in ATP Synthesis: A caution

Sir: The Mg-promoted magnetic isotope effect (MIE), that is a nuclear spin selective over-activation of mitochondrial ATP synthesis by Mg nuclei, has been first discovered and originally described in a pioneer work by Buchachenko et al. [1] published in Cell Biochem. Biophys. back in 2005. Since then, a number of subsequent studies were uncovering some details of its ion–radical mechanism [2–5] with emphasize on potential medicinal applications due to both in vitro and in vivo experiments [6–9]. Obviously, a nuclear–magnetic control over the metal dependent enzymatic catalysis might be affected by traces of any other than Mg magnetic (paramagnetic, ferromagnetic) bivalent cations. In general, a possibility of the nucleotide phosphorylation dysfunctions caused by changes in intra-mitochondrial free metal cations pool was in fact ‘‘stated for alert’’ long ago [10]. As per the role of iron as a powerful suppressor for Mg-MIE in the nucleotidyl kinases directed ATP formation, this became clear just recently [5, 11]. Being attractive to pharmacologists [4, 6–8] and biotechnologists [12], Mg-MIE deserves to be specifically tested for its dependence on iron traces in situ. So we have investigated a correlation between the contents of free Fe in mitochondria isolated from several rat tissues (iron– lacking media employed), and the ATP synthesis rates estimated using these mitochondria in vitro respiration systems [13] in the presence of optimal (20 mM MgCl2) concentrations of either magnetic (Mg) or non-magnetic (Mg) ions [1, 3]. Both A grade isotopes with the enrichment level of not less than 96.4 % were purchased from Gamma Lab SA (Alicante, Spain). ATP synthesis rates were estimated by [p] orthophosphate (6.78–8.45 Ci/mmol, Amersham Radiochemical Centre, UK) incorporation in to de novo synthesized ATP [1] in the in vitro ‘‘breathing’’ mitochondria [13]. Mitochondria were isolated from the following rat tissues: spleen [14], liver [15], skeletal muscles [16], heart muscle [17], kidneys [18], and brain [19]. To get the intra– mitochondrial free iron pool samples, the pre-washed mitochondria pellets were first subjected to Triton X-100/ acetone treatment and then to a triple acetone–extraction of the total low molecular weight compounds fraction [1]. The resulting samples were used to measure the Fe content values by the energy–dispersive X-ray fluorescence spectrometry with a Fe–Zr performance element range employing the XEPOS–HE analytical system (SPECTRO Analytical Instruments, GmbH, Kleve, Germany). As seen from the data obtained (Table. 1), the endogenous mitochondrial-free iron pool level is no doubt critical for ‘‘turning on–off’’ the Mg-magnetic isotope effect expressing in a whole integrative (unbroken) mitochondria, i.e., within their ATP–synthesizing machinery. A. A. Svistunov Y. K. Napolov A. A. Bukhvostov (&) Department of Pharmacology, School of Pharmacy, I. M. Sechenov Moscow State Medical University, Moscow, Russia e-mail: tanzbukh@gmail.com

Possible role of Mg2+ ion in the reaction of organophosphate (dichlorvos) with serine

▸Proposed mechanism for catalytic role of magnesium ion in nucleophic attack of serine to DDVP. ▸Magnesium reduces the pKa of serine hydroxyl group and favors the reaction of serine with DDVP. ▸It is proposed that magnesium acts through a ion radical mechanism. Abstract Organophosphate pesticides (OPs) inhibit both true and pseudo-cholinesterases by reaction with the hydroxyl group of serine in their active sites. Poisoning with OPs is commonly seen in clinics. A common antidote for OP poisoning is atropine but, after ageing and OP dealkylation, even oximes could not be effective. It has been shown that oximes are not always useful in management of OP poisoning. On the other hand, magnesium has been found effective in both clinical and experimental studies. Studies to find more effective antidotes for OP poisoning are in progress. Presently, the possible role of magnesium ion in catalysis of reaction of dichlorvos (2,2-dichlorovinyl dimethyl phosphate, DDVP), a water-soluble OP, with serine is proposed. The hydroxyl group of serine could be a target to which DDVP can react. Nucleophilic attack of pralidoxime to DDVP was previously investigated. To confirm the idea, data were derived from recent and previous research on the role of magnesium in phosphoryl group transfer reactions. Possible reactions of serine and pralidoxime with DDVP in the absence and the presence of magnesium ion were separately investigated theoretically. We propose that the chemical reaction of serine with DDVP exclusively occurs in the presence of a magnesium divalent cation, whereas the reaction of pralidoxime with DDVP occurs independent of the presence of the magnesium ion. The role of the dissociation constant (p K a ) of functional groups in these reactions seems important. It is suggested that application of serine in combination with the magnesium cation can become a more efficient antidote for treatment of OP poisoning.

Enzymic processes as a mechanism of biological magnetoreception

It is shown that enzymatic reactions with electron transfer can play the role of magnetosensitive stages of intracellular processes. The system of von Neumann-Liouville equations for the spin density matrices of the participants of ion-radical enzymatic processes in cells was solved using the steady-state approximation. Within the framework of the Δg mechanism of spin conversion of ion-radical pairs of the substrates of enzymatic reactions, the magnetic-field dependences of the rates of enzymatic processes are calculated. Magnetic field effects can be used as evidence for the ion-radical mechanism of enzymatic reactions and as a means of determining their kinetic characteristics.

Polyfluoroalkylation of pyrrole with 1,2-dibromotetrafluoroethane activated by sulfur dioxide

A possibility of the homogeneous catalytic fluoroalkylation of pyrrole with Freon BrCF2CF2Br using a nitrous base—sulfur dioxide system was shown. The influence of pKa of bases on the occurrence of these processes was studied. The ion-radical mechanism of the processes was substantiated.

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.

Paramagnetic complexes of magnesium as mediators in enzymatic ATP synthesis: DFT calculations of magnetic parameters

Magnetic parameters ( g-factors, hyperfine coupling constants a( 25Mg) and a( 31P)) of paramagnetic pyrophosphate and hydrate magnesium complexes, which model those in catalytic site of the ATP synthesizing enzymes, are calculated. Both g-factors and HFС constants a( 31P) of the paramagnetic pyrophosphate magnesium complexes are identical to those of the pyrophosphate radical. It demonstrates that namely terminal PO 3 group of the liganded ADP in the complex Mg 2+(ADP) 3− donates electron to the Mg ( H 2 O ) n 2 + ion in the primary reaction of the ion-radical mechanism of enzymatic ATP synthesis.

The effect of the oxidative properties of [Mg(H2O)6] in the triplet and singlet states on the energetics of adenosine triphosphate cleavage

The interaction of the adenosine triphosphate (ATP) molecule (the ATP subsystem) with the magnesium complex [Mg(H2O)6]2+ (the Mg subsystem) in the singlet (S) and triplet (T) states in an aqueous medium mimicked by 78 water molecules was studied by the molecular dynamics (density functional theory) method MD DFT:B3LYP with the 6–31G** basis set at T = 310 K. Potential energy surfaces for the S (lowest-lying) and T (highest-lying) states are significantly separated in space. The Mg complex moves along these surfaces to approach either oxygen atoms of the γ-β phosphate groups (O1–O2) (S PES) or oxygen atoms of β-α phosphate groups (O2–O3) (T PES). Chelation of the γ-β β-α and phosphates yields, respectively, a stable low-energy complex ([Mg(H2O)4-(O1–O2)ATP]2−) and a metastable high-energy complex ([Mg(H2O)2-(O2–O3)ATP]2−), which differ in the number of water molecules surrounding the Mg atom. Crossing of two triplet PESs is accompanied by the formation of an unstable state characterized by redistribution of spins between the Mg and ATP subsystems. This state, sensitive to interaction with the 25Mg nuclear spin, induces an unpaired electron spin, which initiates the ATP cleavage by the ion-radical mechanism, yielding a reactive radical ion of adenosine monophosphate (•AMP−), which was earlier found experimentally by the of chemically induced dynamic nuclear polarization (CIDNP) method. Biological aspects of the results obtained are discussed.

Adsorption, electrophysical, and optical studies of the surface of solid solutions and the binary components of the InSb-ZnTe system

Piezoquartz microweighing, surface electroconductivity measurements, and IR and Raman spectroscopies were used to study the mechanism and regularities of the interaction of carbon monoxide, ammonia, and oxygen, gases of different electronic natures encountered in the environment and various technological processes, with the surface of solid solutions and the binary compounds of the InSb-ZnTe system. An analysis of the results with the use of the acid-base and other physicochemical characteristics of the adsorbents and of the electronic properties of the adsorbate molecules showed that the values of adsorption of the gases lie within α = 10−5−10−3 mol/m2. It was demonstrated that, at temperatures above 293 K, the adsorption of CO and NH3 occurs by the donor-acceptor mechanism, whereas oxygen is adsorbed through the ion-radical mechanism, with the predominant participation of coordinatively unsaturated metal atoms and vacancy defects, respectively. It was revealed that the acid-base, adsorption, electrophysical, and optical properties vary similarly with changing composition of the system, a behavior that suggests the same origin of adsorption sites and inherent surface states and makes it possible to predict the adsorption activity of a surface on the basis of its acid-base properties and the properties of the binary compounds and constituent elements. Similarities and distinctions in the behavior of (InSb)x(ZnTe)1 − x solid solutions and the binary compounds (InSb and ZnTe) were identified. Specific features of solid solutions, as multicomponent systems, are that adsorption on them is energetically more favorable, especially well pronounced in the acid-base characteristic-composition and adsorption characteristic-composition diagrams. Such diagrams made it possible to determine the solid solution most active with respect to ammonia, (InSb)0.95(ZnTe)0.05, which was used to make a selective high-sensitivity gas sensor.

Enzymatic Synthesis of Nucleoside Triphosphates. Does It Involve An Ion-Radical Path ?

Accumulation and release of energy in the nucleoside triphosphate enzymatic synthesis and hydrolysis does not limited to a routine energy consuming nucleophilic mechanism. These processes require an overcoming the large energy barrier exceeding a total value of accumulated or released energy level by at least 3 – 4 times (~10 kcal/mol). This energy is supposed to be taken from the mechanical compression of the catalytic site and used to form P–O chemical bond by a direct nucleophilic addition of phosphate to nucleoside diphosphate (ADP as an example). A new, energetically “cheap”, ion-radical mechanism of the ATP biosynthesis has been proposed due to the observation of magnetic isotope and magnetic field effects on the ATP synthesis. This mechanism is about to generate a compression energy to “spend” on a partial dehydratation of magnesium ion inside the nucleotidyl transferase catalyric site (energy cost of this process is 3-5 kcal/mol, i.e. by 2-3 times less than a total accumulated or released energy). Dehydration of this ion is to increase its electron affinity and hence to stimulate an electron transfer from ADP3- to Mg2+. This reaction is a starting point of the ion-radical mechanism considering the molecular mechanics of enzymatic machines and its quantum chemistry background as well. To the contrast of a hardly controllable nucleophilic path, the ion-radical mechanism might be turned on/off by a targeted delivery of paramagnetic magnesium ions, 25Mg2+, towards the phosphate transferring enzyme catalytic site. The magnesium isotope substitution is easily reachable by the endo-osmotic pressure techniques, which makes it attractive for further biotechnological and/or pharmacological application(s).

A Nuclear Spin Selective Control over the DNA Repair Key Enzyme Might Renovate the Cancer–Fight Paradigm. DNA Polymerase Beta to Engage with a Magnetic Isotope Effect

DNA Polymerase Beta (EC 2.7.7.7) is found to be operated by magnetic isotope effect (MIE) of Calcium once the Mg2+ ions replaced with the stable 43Ca2+ isotopes inside the enzyme catalytic sites. The isotope mentioned is the only paramagnetic species of the Calcium isotopic set with a 0.135 natural abundance value and the negative 7/2 nuclear spin providing a nuclear magnetic moment equal to 1.317 Bohr magnetons. As compared to the Mg/40Ca substitution, a 2.25-fold enzyme inhibition has been shown to provethe43Ca-MIE dependent mode of the catalysis turning down.An ion-radical mechanism based on the singlet – triplet conversion of the enzyme generated intermediates (ion-radical pairs) is found to be engaged once the paramagnetic metal isotope involved into the catalysis studied.The MIE promotes a primary reaction in DNA synthesis constituting in electron transfer between the ion – radical forming partners, [Ca(H2O)n2+] and [Ca2+(dNTP)]. Once the metal isotope substitution takes place inside just one of two DNA Polymerase Beta catalytic sites, a consequent43Ca – promoted inhibition leads to a residual synthesis of shorted DNA fragments that counts 25 – 35 nucleotides in length contrasting with the 180n – 210n DNA produced by either intact or40Ca – loaded polymerase. Being occurred simultaneously with a marked MIE – promoted enzyme inhibition, this fact itself makes possible to consider these short (“size-invalid”) DNA segments hardly efficient in the DNA base – excision repair. The latter is a survival factor in leukemic cells where the DNApolβ was found overexpressed. That supports a standpoint considering theDNApolβ a legitimate target for antitumor agents since its inhibition deprives the malignant cell from a DNA base – excision repair in neoplasma. A possible trend making role of these data in the current developments on a novel concept - establishing chemical background for cancer therapies is in a focus.