The role of zinc and its compounds in leukemia.

Zinc is one of the most important microelements necessary for normal body functioning. Zinc is marked in numerous diseases and, hence, its properties and behavior in the body have long been a subject of extensive study. This review considers trends in the assessment of the role of zinc and its compounds in the past decade. It becomes evident that redox-inactive zinc is the main supervisor in the conformation of the most important molecules in all body organs and tissues. We placed emphasis on the variety of zinc-binding sites and the role of zinc in the genesis and progress of different forms of leukemia. The importance of some families of transcription factors in the development and prognosis of treatment of various leukemia forms is examined; new directions of these studies are shown.

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.

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.

Glutamic acid-141: a heme 'bodyguard' in anionic tobacco peroxidase.

The role of the conserved glutamic acid residue in anionic plant peroxidases with regard to substrate specificity and stability was examined. A Glu141Phe substitution was generated in tobacco anionic peroxidase (TOP) to mimic neutral plant peroxidases such as horseradish peroxidase C (HRP C). The newly constructed enzyme was compared to wild-type recombinant TOP and HRP C expressed in E. coli. The Glu141Phe substitution supports heme entrapment during the refolding procedure and increases the reactivation yield to 30% compared to 7% for wild-type TOP. The mutation reduces the activity towards ABTS, o-phenylenediamine, guaiacol and ferrocyanide to 50% of the wild-type activity. No changes are observed with respect to activity for the lignin precursor substrates, coumaric and ferulic acid. The Glu141Phe mutation destabilizes the enzyme upon storage and against radical inactivation, mimicking inactivation in the reaction course. Structural alignment shows that Glu141 in TOP is likely to be hydrogen-bonded to Gln149, similar to the Glu143-Lys151 bond in Arabidopsis A2 peroxidase. Supposedly, the Glu141-Gln149 bond provides TOP with two different modes of stabilization: (1) it prevents heme dissociation, i.e., it 'guards' heme inside the active center; and (2) it constitutes a shield to protect the active center from solvent-derived radicals.

Spin biochemistry: magnetic 24Mg-25Mg-26Mg isotope effect in mitochondrial ADP phosphorylation.

The rates of adenosine triphosphate (ATP) production by isolated mitochondria and mitochondrial creatine kinase incubated in isotopically pure media containing, separately, (24)Mg(2+), (25)Mg(2+), and (26)Mg(2+) ions were shown to be strongly dependent on the magnesium nuclear spin and magnetic moment. The rate of adenosine 5'-diphosphate phosphorylation in mitochondria with magnetic nuclei (25)Mg is about twice higher than that with the spinless, nonmagnetic nuclei (24,26)Mg. When mitochondrial oxidative phosphorylation was selectively blocked by treatment with 1-methylnicotine amide, (25)Mg(2+) ions were shown to be nearly four times more active in mitochondrial ATP synthesis than (24,26)Mg(2+) ions. The rate of ATP production associated with creatine kinase is twice higher for (25)Mg(2+) than for (24,26)Mg and does not depend on the blockade of oxidative phosphorylation. There is no difference between (24)Mg(2+) and (26)Mg(2+) effects in both oxidative and substrate phosphorylation. These observations demonstrate that the enzymatic phosphorylation is a nuclear spin selective process controlled by magnetic isotope effect. The reaction mechanism proposed includes a participation of intermediate ion-radical pairs with Mg(+) cation as a radical partner. Therefore, the key mitochondrial phosphotransferases work as a magnesium nuclear spin mediated molecular machines.

Magnetic isotope effect of magnesium in phosphoglycerate kinase phosphorylation.

Phosphoglycerate kinase (PGK) is found to be controlled by a (25)Mg(2+)-related magnetic isotope effect. Mg(2+) nuclear spin selectivity manifests itself in PGK-directed ADP phosphorylation, which has been clearly proven by comparison of ATP synthesis rates estimated in reaction mixtures with different Mg isotopy parameters. Both pure (25)Mg(2+) (nuclear spin 5/2, magnetic moment +0.85) and (24)Mg(2+) (spinless, nonmagnetic nucleus) species as well as their mixtures were used in experiments. In the presence of (25)Mg(2+), ATP production is 2.6 times higher compared with the yield of ATP reached in (24)Mg(2+)-containing PGK-based catalytic systems. The chemical mechanism of this phenomenon is discussed. A key element of the mechanism proposed is a nonradical pair formation in which (25)Mg(+) radical cation and phosphate oxyradical are involved.

On various possibilities in pulsed radiation biochemistry and chemistry.

Several experiments are described that relate to the application of new regimes of radiation action on enzymes in vitro and some other materials. These regimes have recently come into practice due to the appearance of a new generation of devices with very short high-energy pulses of ionizing radiation. It is shown that the term "flash radiation biochemistry" in its perfect sense has to be used at the condition of the overlapping individual effective interaction microvolumes (e.g. spurs and blobs) realized during a time interval (radiation pulse duration) that is low compared with the corresponding physical-chemical process. In this situation a number of unexpected effects occur at very low absolute doses. These processes are analyzed in terms of their non-stationary and non-diffusive developments.

A novel electrophoretic technique designed to modify the ratio of magnesium isotopes inside the creatine kinase active sites. A preliminary report.

A simple and efficient preparative electrophoretic technique has been proposed to obtain a modified creatine kinase (CK, E.C.2.7.3.2) molecule with an increased content of 25Mg in the active site. A key point of the method is the special design of a 0.9 x 12.0 cm column for ascendent electrophoresis, packed consecutively, from the bottom to the top, with layers of 30 % PAAG (polyacrylamide grade), 25Mg2+ -containing 7.5 % PAAG, enzyme-binding ADP Sepharose and 2.2 % agarose gels, based on different tris-glycine and tris-HCl separation buffer systems. The isotope substitution process was a result of simultaneous desorption of enzyme from ADP Sepharose and electrically directed extensive flow of 25Mg2+ cations through the porous gel matrix. Greater than 8-fold 25Mg enrichment, i.e. a 10.2-86.3 % increase of 25Mg contribution to total enzyme magnesium, has been reached. The modified 25Mg-rich CK samples manifest higher (2.4-fold increase) values of specific catalytic activity when compared with intact (control) ones.