Chromatographic Zinc Isotope Separation by Chelating Exchange Resin

Zinc isotope separations were studied by displacement chromatography using the chelating properties of malate, citrate and lactate exchange resin and EDTA as ligands. After each chromatographic operation, the heavier zinc isotopes were found to preferentially fractionated into the carboxylate complex solution phase. The separation coefficients (ε) for zinc isotope separation had the largest value and were obtained for the isotopic pairs ⁶⁸Zn/⁶⁴Zn (7.16 × 10^?4) and ⁶⁶Zn/⁶⁴Zn (3.08 × 10^?4), respectively, at 298 ± 1 K. The separation coefficient per unit mass differences (ε/ΔM) for the isotopic pair of ⁶⁸Zn/⁶⁴Zn was found to range around 1.55 × 10^?4.     

Effect of the 67Zn isotope on leukemic cells and normal lymphocytes

Porphyrinofullerene nanoparticles (NP) containing magnetic isotopes ²⁵Mg and ⁶⁷Zn (²⁵Mg-NP and ⁶⁷Zn-NP) and the natural isotopic composition of zinc (Zn) were tested on human leukemic cells of patients with acute leukemia and on lymphocytes of healthy donors. The fundamental differences in the cytotoxic effect of magnetic and nonmagnetic zinc isotopes on tumor cells were observed, as well as the complete absence of the influence of the magnetic magnesium isotope and pristine nanoparticles. The ⁶⁷Zn-NP manifested high cytotoxicity towards cells of acute B-lymphoblast leukemia with LD₅₀ almost three times lower than that of healthy donors and four times lower than that of the Zn-NP. Apoptosis was evaluated by cytofluorimetry for the drugs used.     

Tuning Immobilized Commercial Lipase Preparations Features by Simple Treatment with Metallic Phosphate Salts

Four commercial immobilized lipases biocatalysts have been submitted to modifications with different metal (zinc, cobalt or copper) phosphates to check the effects of this modification on enzyme features. The lipase preparations were Lipozyme^®TL (TLL-IM) (lipase from Thermomyces lanuginose), Lipozyme^®435 (L435) (lipase B from Candida antarctica), Lipozyme^®RM (RML-IM), and LipuraSelect (LS-IM) (both from lipase from Rhizomucor miehei). The modifications greatly altered enzyme specificity, increasing the activity versus some substrates (e.g., TLL-IM modified with zinc phosphate in hydrolysis of triacetin) while decreasing the activity versus other substrates (the same preparation in activity versus R- or S- methyl mandelate). Enantiospecificity was also drastically altered after these modifications, e.g., LS-IM increased the activity versus the R isomer while decreasing the activity versus the S isomer when treated with copper phosphate. Regarding the enzyme stability, it was significantly improved using octyl-agarose-lipases. Using all these commercial biocatalysts, no significant positive effects were found; in fact, a decrease in enzyme stability was usually detected. The results point towards the possibility of a battery of biocatalysts, including many different metal phosphates and immobilization protocols, being a good opportunity to tune enzyme features, increasing the possibilities of having biocatalysts that may be suitable for a specific process.     

Neutron activation of traces in electrolytic zinc sulphate solutions : Simultaneous determination of mercury,uranium and ytterbium

A neutron activation determination of traces of mercury, uranium and ytterblum in electrolytic zinc sulphate solutions has been devised The isotope ¹⁹⁷Hg was measured by means of its 68-and 77-keV photopeaks Uranium was determined by measurements of the 106-keV photopeak of the ²³⁹Np daughter activity The 50- and 53-keV X-rays of ytterbium isotopes ¹⁹⁹Yb and ¹⁷⁵Yb were counted using a 1-mm thick Nal(Tl) wafer crystal The chemical separation was performed on anion-exchange resin. The matrix activities were eliminated in 185N hydrofluoric acid while the neptunium and ytterbium activities were desorbed with 5N hydrochloric acid Mercury was eluted from the column with 0.5 M thourea-0.005 N hydrochloric acid and precipitated as sulpinde     

In vitro synthesis of (1→3)-β-D-glucan (callose) and cellulose by detergent extracts of membranes from cell suspension cultures of hybrid aspen

The aim of this work was to optimize the conditions for in vitro synthesis of (1→3)-β-D-glucan (callose) and cellulose, using detergent extracts of membranes from hybrid aspen (Populus tremula × tremuloides) cells grown as suspension cultures. Callose was the only product synthesized when CHAPS extracts were used as a source of enzyme. The optimal reaction mixture for callose synthesis contained 100 mM Mops buffer pH 7.0, 1 mM UDP-glucose, 8 mM Ca²⁺, and 20 mM cellobiose. The use of digitonin to extract the membrane-bound proteins was required for cellulose synthesis. Yields as high as 50% of the total in vitro products were obtained when cells were harvested in the stationary phase of the growth curve, callose being the other product. The optimal mixture for cellulose synthesis consisted of 100 mM Mops buffer pH 7.0, 1 mM UDP-glucose, 1 mM Ca²⁺, 8 mM Mg²⁺, and 20 mM cellobiose. The in vitroβ-glucans were identified by hydrolysis of radioactive products, using specific enzymes. ¹³C-Nuclear magnetic resonance spectroscopy and transmission electron microscopy were also used for callose characterization. The (1→3)-β-D-glucan systematically had a microfibrillar morphology, but the size and organization of the microfibrils were affected by the nature of the detergent used for enzyme extraction. The discussion of the results is included in a short review of the field that also compares the data obtained with those available in the literature. The results presented show that the hybrid aspen is a promising model for in vitro studies on callose and cellulose synthesis.     

Microanalytical isotope ratio measurements and elemental mapping using laser ablation ICP-MS for tissue thin sections: zinc tracer studies in rats

The kinetics of zinc absorption, metabolism and excretion is extensively studied by nutritionists. Stable isotopes of zinc can be used to identify body zinc compartments that have different turnover kinetics. Since the compartments might belong to physiological subsections of different organs, there is a need for microsampling analysis to determine isotope ratios of the trace element zinc in tissue samples. Here, we study the feasibility to use laser ablation coupled to quadrupole ICP-MS for the determination of zinc tracers given to rats at different time points with the aim to generate isotope ratio bioimages of heart tissue. A double tracer (⁷⁰Zn and ⁶⁷Zn) experiment with rats was designed to label the exchangeable zinc pool as well as the stable zinc pool. The isotope ratios determined by laser ablation ICP-MS were evaluated by additional measurements of tissue digests. Accumulated tracers which made up more than 0.1% of total zinc could be identified in the tissues of the treated rats. It was established that at least 50 measurements from the microsampling were necessary to distinguish between controls and a tracer treated rat resulting in reduced resolution of the bioimage. With the parameters used, features in the tissue thin sections of at least 250 μm² in size are necessary to detect the incorporation of a tracer. When different time points have to be measured, higher precisions are required and therefore a larger area needs to be ablated (1 mm²). Using the bioimages and pool measurements from one physiological feature, it was possible to show that the aorta cell walls incorporate the zinc tracer at the different time points.     

Isotope ratio determinations by inductively coupled plasma/mass spectrometry for zinc bioavailability studies

A method is described for the measurement of ⁶⁷Zn/^6*Zn and ⁷⁰ZN/⁶⁸Zn ratios by inductively coupled plasma/mass spectrometry with ultrasonic nebulization. The method provides sufficient accuracy and precision for zinc bioavailability studies that use samples of human feces or blood plasma. Extraction of zinc from ashed samples yields aqueous solutions sufficiently devoid of matrix ions that could affect count rates and isotope ratios. Effects of sodium matrix, zinc concentration, and instrumental parameters on the precision of isotope ratio determinations are documented. Additions of spikes enriched in ⁶⁷Zn and ⁷⁰Zn to natural-abundance fecal samples verify that ratios can be determined on solutions 30 μM in zinc (<300 nmol of zinc per sample) with relative accuracies of <1% and relative standard deviations (r.s.d.) of ?1% over the range from natural abundance to 370 atom% excess of ⁷⁰Zn and to 84 atom% excess of ⁶⁷Zn.     

Isotope shift in hafnium I: Parametric analysis,ab initio calculation,and changes in nuclear charge radii

The isotope shift in the arc spectrum of hafnium was studied in 10 lines for the isotopes¹⁷⁶Hf,¹⁷⁸Hf, and¹⁸⁰Hf by means of a photoelectric recording Fabry-Perot spectrometer with digital data processing. The observed shifts together with results from an earlier study were analyzed by means of the parametric method. The field shift difference between the terms 5d ³(⁴ F) 6s ⁵ F and³ F resulted in 17(2) mK for the isotope pair^178,180Hf. This reflects the influence of a second-order effect which is described by the parameterg ₂=?4.4(6) mK. The parameterz _5d , displaying the magnitude of spin-dependent effects in the isotope shift of 5d ³6s, was found to be 0.8(2) mK for the same isotope pair. The experimental data are compared with results obtained from the non-relativistic Hartree-Fock method. The calculated electron densities describe the experimental field shifts with good accuracy. Hartree-Fock screening ratios for various types of transitions were used to evaluate changes in mean-square nuclear charge radii. The mean value ofλ ^178,180≈δ〈r ²〉^178,180 equals 0.069(10) fm².     

Characterization of neutron transmuted zinc traces in pure copper materials by isotope dilution mass spectrometry

The neutron transmutation doping (NTD) of highly pure copper with zinc was investigated as a promising means of achieving controlled gradation of the zinc content in the range 1–20 μg g^–1. The doping process leads to the enrichment of two stable isotopes ⁶⁴Zn and ⁶⁶Zn in a ratio which differs from that of natural isotopic distribution. Mass spectrometric investigations by thermal ionization mass spectrometry (TIMS) were performed to validate the results obtained by gamma spectrometry. The investigations included both determination of the isotopic ratios of the doped zinc isotopes and the analysis of the accumulated zinc contents by isotope dilution (ID) analysis. Thereby a sample-specific correction of the blank could be performed because the isotope ⁶⁸Zn was not influenced, because of the transmutation process. The results obtained by TIMS prove the strict proportionality of the doped zinc content, in the range 5 to 20 μg g^–1, to the neutron fluence. Comparison with gamma spectrometric results showed a very good agreement within the uncertainties.     

1H- and13 C-NMR Studies of Polymerization of 2,3-Dideuteromethyloxirane with Zinc Dialkoxide

The deuterium-decoupled 100 MHz ¹H-NMR spectra of 2,3-dideuteromethyloxirane and its polymer prepared with a lattice-disordered zinc dialkoxide were analyzed with consideration of the deuterium isotope effects on proton chemical shifts. The results of ¹H- and ^l3C-NMR studies indicated that the initiator for methyloxirane polymerization catalyzed by the diethylzinc-alcohol system was a lattice-disordered zinc dialkoxide, from the aspect of stereoregularity of the polymers obtained.     

Zinc-containing derivatives of 2-aminopyrimidine

A platform containing three anticancer components is proposed. The components are a radioactive ⁶⁹mZn isotope and zinc complexes, where both zinc and ligand exhibit anticancer properties. Two zinc-containing complexes, namely (2-AP)₂ZnCl₂ and (2-AP)₂Zn(Sal)₂ (AP is 2-aminopyrimidine, Sal is salicylate) were synthesized and characterized. Their cytotoxicity with respect to some leukemia cell lines is demonstrated. Their stability in physiological solution and percentage of apoptosis (by flow cytometry) are investigated. Stable complexes of compounds with the isotope ⁶⁹mZn were characterized by TLC and autoradiography.     

Parametric analysis andab initio calculation of isotope shifts in rhenium I

The isotope shift in the arc spectrum of rhenium was studied in 12 lines for the highly enriched isotopes¹⁸⁵Re and¹⁸⁷Re by means of a photoelectric recording Fabry-Perot spectrometer with digital data processing. The observed shifts together with results from earlier studies were analyzed by means of the parametric method. The field shift difference between the terms 5d ⁶(⁵ D)6s ⁶ D and⁴ D was found to be 40 (5) mK, showing the influence of second-order effects. The parameterz _5d , displaying the magnitude of spin-dependent effects in 5d ⁶6s, was found to be 1.3 (8) mK. The experimental data are compared with results from non-relativistic Hartree-Fock calculations. The calculated electron densities describe the measured isotope shifts with good accuracy.     

Nuclear spin catalysis in biochemical physics

Magnetic isotope effects have been recently discovered in living nature. They were observed for the first time in experiments on cells enriched with various magnesium isotopes, magnetic ²⁵Mg or non-magnetic ones. A catalytic effect of the magnetic isotope of magnesium was discovered in experiments with myosin, the most important biomolecular motor utilizing the energy of ATP to perform mechanical work. The rate of ATP hydrolysis with the magnetic ²⁵Mg isotope is 2.0–2.5 times higher than that obtained with nonmagnetic ²⁴Mg or ²⁶Mg. A similar effect of the nuclear spin catalysis was experimentally observed for zinc isotopes. The rate of ATP hydrolysis in the case of magnetic ⁶⁷Zn increased by 40–50% as compared to that observed experimentally for nonmagnetic isotopes (⁶⁴Zn or ⁶⁸Zn). Catalytic effects of the magnetic isotope of magnesium were also experimentally found for H⁺-ATPase isolated from yeast mitochondria and ATPase of the plasma membrane of the myometrium. The magnetic isotope effect indicates unambiguously that the chemomechanical processes involve a limiting step catalyzed by biomolecular motors, which depends on the electronic spin state, and that this step is accelerated in the presence of nuclear spin of the magnetic isotope.

     

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.     

Substoichiometric isotope dilution analysis of copper traces in zinc by adsorptive sampling

The spontaneous deposition of Cu²⁺ from aqueous solutions on a hydrogen-saturated platinum surface as a possibility for the substoichiometric sampling of copper is shown. A sensitive isotope dilution method has been developed for the determination of traces of copper in high purity zinc making use of the spontaneous deposition of microquantities of Cu²⁺ from aqueous solutions of zinc salts on a cathodically polarized platinum surface. If the same platinum surface is used in each run, the saturation values of the deposited copper are practically independent of the concentrations and contents of copper and zinc in the solution. The copper traces were labelled with the product of the⁶⁴Zn(n,p)⁶⁴Cu nuclear reaction. A copper content of 0.18±0.03 ppm in zinc was determined by this method.     

Precise determination of isotopic ratios for some biologically significant elements by inductively coupled plasma mass spectroscopy

Isotope ratios for copper, iron, lead, lithium, nickel and zinc were measured with an ELAN 5000 ICP-MS instrument. Except for lithium isotopes, ratio relative standard deviations (RSDs) of about 0.1% were achieved with measurement times of 10 min or less per sample on isotope pairs that differed by no more than a factor of 10 in abundance. It was necessary to accumulate several million counts to reduce statistical counting errors, to correct for the dead time in the counting circuitry, and to compensate for a slow drift of apparent ratios with time. Drift compensation was achieved by using a third isotope of the test element, by adding two internal standard elements with isotopes bracketing the mass range of interest, or by frequent recalibration with a standard of known abundances. Attempts to compensate for drift in lithium isotope ratios were not successful and typical RSDs for ⁶Li/⁷Li remained around 0.5%. Copper and zinc ratios were measured in pig feces with ratio precision and drift behavior essentially identical to that seen for synthetic solutions.     

Effect of Solution pH and Composition on Horse Liver Alcohol Dehydrogenase Thermostability

The influence of solution composition (pH, salts, and chelant) on the thermostability of horse liver alcohol dehydrogenase was studied by differential scanning calorimetry (DSC) in the pH range from7.51 to 9.50 and showing the enzyme catalytic activity. The experiments demonstrated that the effect of increasing pH on the heat denaturation temperature of the enzyme was slight, but the denaturation enthalpy was considerably increased, indicating the enzyme conformation alteration by changing pH and the presence of enthalpy-entropy compensation. The effect of ionic strength on thermostability was not noticeable, i.e., the electrostatic interactions were not a dominant factor for the thermostability. The anions Cl⁻ and SCN⁻ imposed diverse influence upon the enzyme thermostability, and SCN⁻can reduce the thermostability considerably. The chelant 1,10-phenanthroline, which can reversibly bind together with the zinc ions functioning the catalytic action in the enzyme molecules, increases the thermostability considerably. The hydration of the enzyme plays an important role to the thermostability. This revised version was published online in July 2006 with corrections to the Cover Date.     

5-氟尿嘧啶卟啉锰/锌配合物的合成、光电性质及抗癌活性

合成了新型5-氟尿嘧啶修饰的自由卟啉5-(2-(5-氟尿嘧啶-3-基)乙氧基苯基)-10,15,20-三苯基卟啉(L)及其锰配合物(MnL)和锌配合物(ZnL)。通过紫外-可见光谱、红外光谱、核磁共振氢谱及高分辨质谱等手段进行了结构表征。研究了它们的荧光性质和电化学性质;应用标准磺酰罗丹明B法(SRB法)测试了目标化合物对人肺癌细胞株A549、人肝癌细胞株Bel-7402和人结肠癌细胞株HCT-8生长的抑制活性。结果表明:相同实验条件下,不同金属离子对配合物的荧光强度存在较大影响:锌配合物具有荧光猝灭的性质,而锰配合物未能观察到明显的荧光发射光谱;与自由卟啉和锌配合物相比,锰配合物除卟啉环发生氧化还原反应外,Mn~(2+)自身也发生了氧化还原反应;抗癌活性测试显示锰配合物较其他2种化合物有较好的抗癌活性。     

Application of the total evaporation technique to chromium isotope ratio measurement by thermal ionization mass spectrometry

The total evaporation technique of thermal ionization mass spectrometry was applied to the isotopic analysis of chromium. High measurement reproducibility of the chromium isotope ratios was verified (2 S.E. < 0.05% (⁵³Cr/⁵²Cr)), while a clear mass fractionation effect was observed by using conventional measurement technique. The chromium isotope ratios analyzed by the total evaporation method were not affected by the sample amount on the rhenium filament (50-500 ng Cr). The isotopic analysis under the coexistence of zinc was also performed, and its effect to the chromium isotope ratios was confirmed.     

Isotope shift measurements in zirconium by Doppler-free laser polarization spectroscopy

Isotope shifts in 17 transitions of ZrI have been measured by Doppler-free laser polarization spectroscopy in a hollow cathode discharge. The results were combined with other known isotope shift data of ZrI and tested for consistency in a multidimensional King plot. By including values ofδ〈r ²〉 deduced from optical isotope shifts mass and field shifts were separated, and improved values ofδ〈r ²〉 could be determined from the King plot. The results for the isotope pairs A, A′ are as follows; 90, 92: 0.244(43) fm²; 92, 94: 0.176(20) fm²; 94, 96: 0.126(23) fm².