Concentrations Of Nickel Chloride Research Articles

Ni-B-PTFE Nanocomposite Co-Deposition on the Surface of 2A12 Aluminum Alloy.

The spinning cup, a crucial component of textile equipment, relies heavily on 2A12 aluminum alloy as its primary raw material. Commonly, electroplating and chemical nickel-phosphorus (Ni-P) plating are employed to improve the surface characteristics of the object. Nevertheless, due to the growing expectations for the performance of aluminum alloys, the hardness and wear resistance of Ni-P coatings are no longer sufficient to fulfill industry standards. This study primarily focuses on the synthesis of Ni-B-PTFE nanocomposite chemical plating and its effectiveness when applied to the surface of 2A12 aluminum alloy. We examine the impact of the composition of the plating solution, process parameters, and various other factors on the pace at which the coating is deposited, the hardness of the surface, and other indicators of the coating. The research findings indicate that the composite co-deposited coating achieves its optimal surface morphology when the following conditions are met: a nickel chloride concentration of 30 g/L, an ethylenediamine concentration of 70 mL, a sodium borohydride concentration of 0.6 g/L, a sodium hydroxide concentration of 90 g/L, a lead nitrate concentration of 30 mL, a pH value of 12, a temperature of 90 °C, and a PTFE concentration of 10 mL/L. The coating exhibits consistency, density, a smooth surface, and an absence of noticeable pores or fissures. The composite co-deposited coating exhibits a surface hardness of 1109 HV0.1, which significantly surpasses the substrate's hardness of 232.38 HV0.1. The Ni-B-PTFE composite coating exhibits an average friction coefficient of around 0.12. It has a scratch width of 855.18 μm and a wear mass of 0.05 mg. This coating demonstrates superior wear resistance when compared to Ni-B coatings. The Ni-B-PTFE composite coating specimen exhibits a self-corrosion potential of -6.195 V and a corrosion current density of 7.81 × 10-7 A/cm2, which is the lowest recorded. This enhances its corrosion resistance compared to Ni-B coatings.

Bioaccumulation and Depuration Dynamics of Nickel Chloride in Nile Tilapia (Oreochromis niloticus) Exposed to Sub-lethal Concentrations

The current objective of this research is to examine the bioaccumulation and subsequent depuration levels of nickel chloride within vital organs such as the gills, liver, and kidney of Oreochromis niloticus under controlled laboratory conditions. The fish were subjected to exposure under two sub-lethal concentrations, i.e., 1/5th (9.39 ppm) and 1/10th (4.69 ppm), for 28 days of absorption and subsequently transferred to uncontaminated, good aerated water for 28days of elimination (depuration). Following 28 days of exposure to lower sub-lethal and higher sub-lethal nickel chloride concentrations, the sequence of bioaccumulation of nickel chloride in organs was observed as kidney > liver > gills. The depuration trend for higher and lower concentrations was gills> liver > kidney. The kidney exhibited the highest accumulation of Ni. Meanwhile, the Ni depuration in the gills was significantly (p<0.05) more when compared to other routes following exposure to both concentrations. This research assessed nickel chloride's bioaccumulation and depuration dynamics in Oreochromis niloticus, providing insights into its physiological responses to metal exposure. The study concludes that nickel accumulates predominantly in the kidney, with gills exhibiting the highest depuration rates, highlighting the importance of understanding metal uptake and elimination mechanisms in aquatic organisms for effective pollution management.

The Influence of Selected Transition Elements on Cell Metabolism

Abstract The elements are present in the environment. Moreover, they are used in pharmacy and the production of new materials used in medical applications. They are often as environmental pollutants. They can accumulate in organisms and induce toxic effects on the cellular level. HepG2, L929 and Caco-2 cell lines were exposed to known concentrations of chromium chloride, iron chloride, nickel chloride, molybdenum trioxide and cobalt chloride (200 or 1000 μ M used alone and in combinations). Concentrations of chromium, iron, nickel, molybdenum and cobalt in the cell lysate and the culture medium were determined by ICP-MS. Moreover, sodium, potassium, calcium and magnesium concentrations were also measured. What is more, cells were observed under light and scanning electron microscope. The dose-dependent increase in the concentration of chromium, iron, nickel, molybdenum and cobalt in all cell lines after incubation with elements was observed. Potassium concentration decreases while sodium calcium and magnesium increase after incubation of cells with of mentioned elements. The incubation of cells with microelements induces cell morphology changes. The presented study shows the crucial role of tested microelements in the induction of cell death as a result of an imbalance of sodium, potassium, calcium and magnesium concentration inside the cell.

Exploring the potential of nickel-chloride bath for electroforming of pure nickel and nickel composites

Electroforming is becoming increasingly important as a reliable method for the production and replication of independent parts. Researchers are continually striving to reduce production costs for the fabrication of complex tools with the highest precision and lowest cost, and electroforming is a key technique for achieving this goal. The present research aimed to produce pure nickel foils via electroforming using a simple and inexpensive nickel-chloride bath, which has not been previously utilized for electroforming. The effects of saccharin concentration, nickel-chloride concentration, direct current density, and the use of graphite as an insoluble anode were investigated. The surface morphology of the electroformed products was characterized through scanning electron microscopy (SEM) and their chemical composition was analyzed using energy dispersive x-ray (EDX) and x-ray diffraction (XRD) pattern. The microhardness of the foils was determined using the Vickers hardness test. Results showed that specimens produced using the nickel-chloride bath had a good surface appearance with acceptable brightness and satisfactory microhardness. Ten electroforming tests were conducted to determine the optimal bath components, pH, and direct current density for the fabrication of pure nickel products. It was found that these parameters had a significant influence on the quality of the appearance and surface morphology of the foils. In addition, using a graphite anode was seen to reduce the cathode current efficiency as compared to a soluble nickel anode and was affected by the preferred orientation of nickel crystal plates. It can be concluded that the nickel-chloride bath has excellent potential for the production of pure nickel products using the electroforming method.

Electrochemical Behavior of Dysprosium Ion and Its Co-Electroreduction with Nickel Ions in the Molten KCl-NaCl-CsCl Eutectic

The electrochemical behavior of dysprosium ions, as well as dysprosium and nickel ion co-reduction, on inert tungsten electrodes and active nickel electrodes were studied in the eutectic KCl-NaCl-CsCl melt at a temperature of 823 K using the methods of cyclic and square-wave voltammetry and open circuit chronopotentiometry. The process of Dy3+ ions electroreduction was found to be reversible and to proceed within a single three-electron stage up to the polarization rate of 0.1 V/s. The increase in the polarization rate indicates a slower rate of the charge transfer, which causes the quasi-reversible character of the charge transfer. It is shown that when the KCl-NaCl-CsCl eutectic melt contains both nickel and dysprosium ions, the voltammetry curves at 823 K have a wave of nickel ion reduction at the potentials of −(0.22–0.28) V and a dysprosium ion reduction at the potentials of −(2.175–2.250) V relative to a chlorine-silver reference electrode. Apart from these waves, the voltammograms have two reduction waves at the potentials of −(1.9–1.95) V and −(2.05–2.1) V. These waves are associated with the reduction of dysprosium ions and their depolarization on metallic nickel, which was preliminary deposited on the tungsten electrode, as well as the formation of the intermetallic phases of dysprosium and nickel of various DyxNiy compositions. The (E-t) dependencies of the open circuit chronopotentiometry elucidate plateaus of the potential delay, which correspond to the dissolution of separate dysprosium and nickel intermetallic phases. Based on the results of the voltammetry changes and the chronopotentiometry of the open circuit, a series of electrochemical syntheses were performed in the potentiostatic regime at the potentials of −(1.7–2.1) V. The intermetallic phases of DyNi5, DyNi3 and DyNi2 were obtained at a definite ratio of the dysprosium and nickel chloride concentrations in the KCl-NaCl-CsCl eutectic melt and at a temperature of 823 K. The synthesized intermetallic samples were characterized by X-ray diffraction and scanning electron microscopy.

Nickel chloride removal and insights into heavy metal removal by hydrate-based method

Heavy metal ion in waste water can be potential treated by hydrate formation and dissociation. In this work, nickel chloride was chosen for preparing heavy metal solution, which was then removed by forming methane (CH4) hydrate. Four common factors of stirring speed, hydration time, temperature, and concentration were considered respectively. The nickel chloride removal efficiency reached 71.8% with the dissociated water of 44.9% for the stirring speed, hydration time, temperature, and nickel chloride concentration of 400 r/min, 1 h, 271.1 K, and 100 ppm, respectively. Adhered heavy metal solution on the hydrate surface resulted in the impurity of heavy metal removal by hydrate-based method, and wrapped heavy metal solution by accumulated hydrate was another main reason for the impurity of heavy metal removal. In addition, a flushing water method was proposed and conducted. Nickel chloride removal efficiency was improved to 89.5% with the yield of dissociated water of 44.2%. Finally, controlling hydrate formation conditions and combining hydrate-based method with other method were also proposed to enhance the heavy metal removal efficiency.

Hydrothermal Synthesis of Nickel Oxide and Its Application in the Additive Manufacturing of Planar Nanostructures

The hydrothermal synthesis of nickel oxide in the presence of triethanolamine was studied. Furthermore, the relationship between the synthesis conditions, thermal behavior, crystal structure features, phase composition and microstructure of semi-products, and the target oxide nanopowders was established. The thermal behavior of the semi-products was studied using a simultaneous thermal analysis (in particular, using one that involved thermogravimetric analysis and differential scanning calorimetry, TGA/DSC). An X-ray diffraction (XRD) analysis revealed that varying the triethanolamine and nickel chloride concentration in the reaction system can govern the formation of α- and β-Ni(OH)2-based semi-products that contain Ni(HCO3)2 or Ni2(CO3)(OH)2 as additional components. The set of functional groups in the powders was determined using a Fourier-transform infrared (FTIR) spectroscopy analysis. Using microextrusion printing, a composite NiO-(CeO2)0.80(Sm2O3)0.20 anode film was fabricated. Using XRD, scanning electron microscopy (SEM), and atomic force microscopy (AFM) analyses, it was demonstrated that the crystal structure, dispersity, and microstructure character of the obtained material correspond to the initial nanopowders. Using Kelvin probe force microscopy (KPFM) and scanning capacitance microscopy (SCM), the local electrophysical properties of the printed composite film were examined. The value of its conductivity was evaluated using the four-probe method on a direct current in the temperature range of 300-650 °C. The activation energy for the 500-650 °C region, which is of most interest in the context of intermediate-temperature SOFCs working temperatures, has been estimated.

Effects of Combined Stresses of Salinity (NaCl) and Heavy Metal (NiCl2) Levels on Seed Germination and Growth of Citrullus colocynthis l.

Salinity and heavy metal stresses are a great hindrance to the germination and development of plants. Nickel (Ni) is an indispensable micronutrient for plants at low concentrations. However, the proficiency depends upon the plant types. Citrullus colocynth is a medicinal cucurbit weed. The contemporary target of the study is to appraise the influence of combined stresses by varying concentrations of sodium chloride and nickel chloride on germination, morphology, biochemical ions, and physiology of C. colocynth. Germination percentage, root length, shoot length, fresh weight, dry weight, number of leaves, Na+, K+, Ca++, Cl-, Ni+, chlorophyll a and b, proline, SOD and CAT of C. colocynth were measured with nine combined levels (100 mM NaCl + 50 uM NiCl2), (200 mM NaCl + 50 uM NiCl2), (400 mM NaCl + 50 uM NiCl2), (100 mM NaCl + 100 uM NiCl2), (200 mM NaCl +100 uM NiCl2), (400 mM NaCl +100 uM NiCl2), (100 mM NaCl + 200 uM NiCl2), (200 mM NaCl + 200 uM NiCl2) and (400 mM NaCl +200 uM NiCl2). This experiment was conceded out in a completely randomized design with four replications. Germination percentage, root length, shoot length, fresh weight, dry weight, and the number of leaves, K+, Ca++, chlorophyll a, and b decreased by increasing stress levels while Na+, Cl-, Ni+, Proline, SOD, and CAT increased with increasing stress levels. This species has a positive morpho-physiological response under low(100mM NaCl, 50 uM NiCl2) and moderate (200mM NaCl, 100 uM NiCl2) combinations of salt and heavy metals while tolerance was observed under high-stress levels(400mM NaCl, 200 uM NiCl2). It is concluded that this species can be recommended for phytoremdiation against combined salt and heavy metal stresses.

Effect of Coating Bath Parameters on Properties of Electroless Nickel-Boron Alloy Coatings

Electroless nickel-boron binary coatings were obtained with various bath compositions to investigate the effect of bath parameters on tribological and mechanical behaviours of the coating. Characterisation of the coating for surface morphology and phase structure is done using Scanning Electron Microscopy (SEM) and X-ray Diffraction (XRD), respectively, whereas tribological behaviour of coatings is evaluated on a pin-on-disc tribo-tester. Elastic modulus and surface hardness of coatings have been obtained using nano-indentation technique, while the scratch behaviour of the coatings has been determined using micro-scratch test. Corrosion resistance of coatings is also determined. It is observed that surface roughness of the coatings increased with increase in sodium borohydride concentration but decreased slightly with increase in nickel chloride concentration. Friction and wear characteristics are found to increase with surface roughness which occurs due to increased boron content. Surface hardness and scratch hardness are also seen to vary with coating bath parameters.

Production of metallic nickel particles of a given size from nickel (II) salts using sodium borohydride

Fine nickel particles offer an innovative material which can be used, in particular, as a filler in conducting compositions. However, for successful practical application in the above area the size of such particles should not exceed 12 μm. The method of chemical reduction of salts in liquid phase was selected to produce metallic nickel particles with controlled size. Nickel chloride was used as a salt, and sodium borohydride with its high reduction activity – as a reducing agent. The synthesis was carried out in aqueous medium at room temperature with the [BH4–]/[Ni2+] ratio equal to 3.5 mol/mol. The authors looked at the hydrolysis of sodium borohydride in solutions with varying concentrations of alkali and thus determined what concentration of sodium hydroxide would be optimum to stabilize the sodium borohydride solution. Kinetic dependencies of pH and the optical density of the reaction mixture were obtained. Their comparison and analysis helped time-space the processes of nucleation and synthesis suggesting that that was an autocatalytic reaction. The obtained results helped establish that the optimum range of nickel chloride concentrations is 15 to 20 mmol/L. An optical microscope was used to obtain microphotographs of the synthesized particles and determine their sizes as a function of the concentration of the initial salt and the storage time. It was established that the maximum size of the obtained particles in the nickel chloride concentration range of 5 to 20 mmol/L after a week after synthesis was 10 μm. At the same time, when the nickel chloride concentration is 15 to 20 mmol/L, the most probable size of the particles after a week after synthesis is 4–6 μm.This research was funded by the D. Mendeleev University of Chemical Technology of Russia. Project number: G-2020-019.

THE EFFECT OF NiCl2 ON THE OPTICAL PROPERTIES OF POLYVINYL ALCOHOL FILMS

By Wasan Al-Taa'y, Mohammed Abdul Nabi & 1 more. Optical properties of pure and doped polyvinyl alcohol films (PVA), prepared by casting technique with different nickel chloride concentrations have been studied.

Contribution of Seven Electroplating Factors on Some Properties of Zn-Ni Coating on Medium Carbon Steel using Taguchi's L27 Orthogonal Array

The protective Zn-alloy coating enhances the carbon steels' corrosion resistance. Seven factors of Zn-Ni coating electroplating on medium carbon steel were optimized using Taguchi L27 (37) orthogonal array. The impact of nickel chloride concentration (N), distance factor between anode and cathode (X), plating process time (P), bath temperature (T), deposition current density (I), substrate hardness (H), and substrate roughness (R) on the corrosion current density (ICorr) and the coating thickness were examined. Two different samples were also morphologically studied. Results indicated that N:20 g l-1; X:9 cm; P:20 min; T:45 °C; I:3 A dm-2; H:44 HRC; and R:P500 can produce Zn-Ni coating with the highest corrosion resistance (lowest ICorr) with inhibition efficiency of 96.5%. Among factors, T, P, H, and N had the highest impact on ICorr with a total percentage contribution of about 60%. In addition, the thickness was mainly affected by I, P, and H, with a total percentage contribution >90%. The optimal combination for lowest ICorr resulted in a smooth and more homogenous and compact structure of coating without microcracks. Higher microhardness was also obtained due to the high nickel content in Zn-Ni coating (14.7%wt). However, the worst combination gave semi-spherical-shaped crystallites with non-uniform distribution of particles.

Nickel sulphide-reduced graphene oxide composites as counter electrode for dye-sensitized solar cells: Influence of nickel chloride concentration

Nickel sulphide-reduced graphene oxide (NiS-rGO) composite films have been prepared via modified Hummers’s method assisted with spin coating technique. The NiS-rGO samples were then employed as counter electrode in a dye-sensitized solar cell (DSSC). The main aim of this work is to investigate the relationship between the concentrations of NiCl2 with the properties of NiS-rGO and performance parameters of the device. The dominant rGO and minor NiS phase exist in the composite. The morphology of the composite is white strips rGO and NiS agglomerate particle. The element of C, O, Ni and S present in the composite. The highest η of 1.04% and Jsc of 7.39 mA cm−2 were obtained from the device with 0.06 M NiCl2 resulted from the longest carrier lifetime. The photovoltaic parameters results reveal that NiS-rGO composite has potential to become as a free platinum counter electrode of DSSC.

Repeatability and reproducibility of longitudinal relaxation rate in 12 small-animal MRI systems

BackgroundMany translational MR biomarkers derive from measurements of the water proton longitudinal relaxation rate R1, but evidence for between-site reproducibility of R1 in small-animal MRI is lacking. ObjectiveTo assess R1 repeatability and multi-site reproducibility in phantoms for preclinical MRI. MethodsR1 was measured by saturation recovery in 2% agarose phantoms with five nickel chloride concentrations in 12 magnets at 5 field strengths in 11 centres on two different occasions within 1–13 days. R1 was analysed in three different regions of interest, giving 360 measurements in total. Root-mean-square repeatability and reproducibility coefficients of variation (CoV) were calculated. Propagation of reproducibility errors into 21 translational MR measurements and biomarkers was estimated. Relaxivities were calculated. Dynamic signal stability was also measured. ResultsCoV for day-to-day repeatability (N = 180 regions of interest) was 2.34% and for between-centre reproducibility (N = 9 centres) was 1.43%. Mostly, these do not propagate to biologically significant between-centre error, although a few R1-based MR biomarkers were found to be quite sensitive even to such small errors in R1, notably in myocardial fibrosis, in white matter, and in oxygen-enhanced MRI. The relaxivity of aqueous Ni2+ in 2% agarose varied between 0.66 s−1 mM−1 at 3 T and 0.94 s−1 mM−1 at 11.7T. InterpretationWhile several factors affect the reproducibility of R1-based MR biomarkers measured preclinically, between-centre propagation of errors arising from intrinsic equipment irreproducibility should in most cases be small. However, in a few specific cases exceptional efforts might be required to ensure R1-reproducibility.

Selection of the Optimum Electrolysis Bath Composition for the Synthesis of Holmium–Iron Triad Metal Intermetallics

The results of high-temperature electrochemical synthesis of holmium–iron triad metal intermetallics in chloride melts are presented. The influence of the current density, the composition of an electrolysis bath, and the synthesis time on the electrolysis processes and the composition of the end product is studied. The electrolysis of the molten KCl–NaCl mixture containing 0.5–2.5 mol % holmium trichloride and 0.1–2.5 mol % nickel (cobalt) dichloride at a current density of 0.5–2.0 A/cm2, a temperature of 973–1073 K, and an electrolysis time of 30–90 min is shown to cause the formation of a cathode deposit in the form of a “metal–salt pear” on a tungsten electrode. This pear consists of a mixture of metallic nickel (cobalt) and HoNi, HoNi5, and HoNi3 (HoCo2, HoCo3, HoCo5, Ho2Co17) intermetallics. The intermetallic compound content in the cathode deposit is found to increase at a constant current density (1.2 A/cm2) and when the holmium chloride content in a melt or the ratio of the holmium chloride concentration to the nickel (cobalt) chloride concentration increases. Only a mixture of holmium–nickel (cobalt) intermetallics can exist in the cathode deposit if the electrolysis bath composition and the electrolysis parameters are controlled. The electrochemical synthesis of holmium–iron intermetallics was performed under galvanostatic conditions in molten KCl–NaCl–HoCl3. Iron ions are introduced in a melt via the anodic dissolution of metallic iron. The results of X-ray diffraction analysis of the electrolysis products demonstrate the fundamental possibility of synthesizing holmium–iron intermetallics. The optimum conditions of electrosynthesis of holmium–iron triad metal intermetallics are determined.

Optimization of Mechanical Properties of Nickel-Cobalt Coatings from Sulphamate Baths

Nickel-cobalt alloys are important coating materials due to their magnetic properties [1-2],wear resistance [3-4] and electrocatalytic properties [5]. Their deposition from sulfamateelectrolytes has many advantages including low internal stress, homogenous deposition athigh current densities, high current efficiencies and higher hardness as compared to theconventional Watts electrolyte [6]. A statistical experimental design was used to study theeffects of boric acid and nickel chloride concentrations, bath temperature and applied currentdensity on nickel coatings in sulphamate baths. After the optimization of the electrolytecomposition, effects of pH and Co additions to the electrolyte were investigated. The coatingthickness and its distribution were measured by XRF techniques. Microhardness, surfacemorphology and internal stress of coatings were also determined. It was found that Coaddition to the electrolyte and operation at higher pH yielded deposits of higher Co contentand enhanced hardness up to a certain point.

Development of cultures of the marine sponge Hymeniacidon perleve for genotoxicity assessment using the alkaline comet assay.

Sponges are a potential alternative model species to bivalves in pollution biomonitoring and environmental risk assessment in the aquatic ecosystem. In the present study, a novel in vivo exposure sponge culture model was developed from field-collected and cryopreserved sponge (Hymeniacidon perleve) cells to investigate the genotoxic effects of environmentally relevant metals in the laboratory. Sponge cell aggregates were cultured and exposed to noncytotoxic concentrations (0-0.4 mg/L) of cadmium chloride, nickel chloride, and sodium dichromate as quantified by the reduction of 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide and DNA-strand breaks assessed by the comet assay. Reactive oxygen species (ROS) formation was quantified by oxidation of 2',7'-dichlorofluorescin diacetate in sponge cell aggregates exposed to the same concentrations of Cd, Cr, and Ni. There was a statistically significant (p < 0.05) concentration-dependent increase in the level of DNA-strand breaks and ROS formation in all of the metals investigated. To the best of our knowledge, we have utilized for the first time the alkaline comet assay to detect DNA-strand breaks in marine sponge cells and demonstrated that exposure to noncytotoxic concentrations of Cd, Cr, and Ni for 12 h results in a concentration-dependent increase in DNA damage and levels of ROS production. In conclusion, we have developed a novel in vivo model based on culture of cryopreserved sponge cells that is compatible with the alkaline comet assay. Genotoxicity in marine sponges measured by the comet assay technique may be a useful tool for biomonitoring research and risk assessment in aquatic ecosystems. Environ Toxicol Chem 2017;36:3314-3323. © 2017 SETAC.

Effect of nickel chloride on seed germination and morphophysiological parameters of seedlings of Alisma plantago-aquatica L. and Sium latifolium L.

The effect of nickel chloride concentrations in the range of 1–1000 mg/L on seed germination and the development of organs and pigment system in seedlings of the helophyte common water-plantain Alisma plantago-aquatica L. and hygrohelophyte greater water-parsnip Sium latifolium L. has been studied. It is shown that nickel chloride has practically no effect on the germination of the common water-plantain; however, it suppresses the germination of the greater water-parsnip. It is demonstrated that the toxicant suppresses the growth of seedlings and synthesis of photosynthetic pigments. The length of cotyledons and hypocotyl is less variable, with a much stronger effect on roots and leaves. It is determined that the morphometric parameters are less sensitive to the toxicant when compared to physiological ones. In general, the common water-plantain is more resistant to the effect of nickel chloride than the greater water-parsnip.

Nicotinamide N-Methyltransferase Suppression Participates in Nickel-Induced Histone H3 Lysine9 Dimethylation in BEAS-2B Cells

Background: Nickel compounds are well-established human carcinogens with weak mutagenic activity. Histone methylation has been proposed to play an important role in nickel-induced carcinogenesis. Nicotinamide N-methyltransferase (NNMT) decreases histone methylation in several cancer cells by altering the cellular ratio of S-adenosylmethionine (SAM) to S-adenosylhomocysteine (SAH). However, the role of NNMT in nickel-induced histone methylation remains unclear. Methods: BEAS-2B cells were exposed to different concentrations of nickel chloride (NiCl₂) for 72 h or 200 μM NiCl₂ for different time periods. Histone H3 on lysine 9 (H3K9) mono-, di-, and trimethylation and NNMT protein levels were measured by western blot analysis. Expressions of NNMT mRNA and the H3k9me2-associated genes, mitogen-activated protein kinase 3 (MAP2K3) and dickkopf1 (DKK1), were determined by qPCR analysis. The cellular ratio of nicotinamide adenine dinucleotide (NAD⁺) to reduced NAD (NADH) and SAM/SAH ratio were determined. Results: Exposure of BEAS-2B cells to nickel increased H3K9 dimethylation (H3K9me2), suppressed the expressions of H3K9me2-associated genes (MAP2K3 and DKK1), and induced NNMT repression at both the protein and mRNA levels. Furthermore, over-expression of NNMT inhibited nickel-induced H3K9me2 and altered the cellular SAM/SAH ratio. Additionally, the NADH oxidant phenazine methosulfate (PMS) not only reversed the nickel-induced reduction in NAD⁺/NADH but also inhibited the increase in H3K9me2. Conclusions: These findings indicate that the repression of NNMT may underlie nickel-induced H3K9 dimethylation by altering the cellular SAM/SAH ratio.

Biochemical characterization of the hydrogen photoevolution in cyanobacterium Oscillatoria chalybea

The filamentous non-heterocystous cyanobacterium Oscillatoria chalybea showed molecular hydrogen photoevolution under different conditions. The major part of determined hydrogen evolution would be derived from a hydrogenase system distinct from the nitrogenase. To improve the hydrogen production, different buffers, temperatures, pH values and some inorganic cofactors were studied. The results revealed that the best buffer was Tricine-KCl, the optimum temperature was 25 °C, the optimum pH value was within the range 7–7.5 and the optimum concentration of nickel chloride was 50 μM that improved also the growth of O. chalybea. The influence of inorganic cofactors showed that the addition of 10−5 MnCl2 increases the photoevolution of molecular hydrogen.