LINE‐1 hypomethylation induced by reactive oxygen species is mediated via depletion of S‐adenosylmethionine

Whether long interspersed nuclear element‐1 (LINE‐1) hypomethylation induced by reactive oxygen species (ROS) was mediated through the depletion of S‐adenosylmethionine (SAM) was investigated. Bladder cancer (UM‐UC‐3 and TCCSUP) and human kidney (HK‐2) cell lines were exposed to 20 μM H₂O₂ for 72 h to induce oxidative stress. Level of LINE‐1 methylation, SAM and homocysteine (Hcy) was measured in the H₂O₂‐exposed cells. Effects of α‐tocopheryl acetate (TA), N‐acetylcysteine (NAC), methionine, SAM and folic acid on oxidative stress and LINE‐1 methylation in the H₂O₂‐treated cells were explored. Viabilities of cells treated with H₂O₂ were not significantly changed. Intracellular ROS production and protein carbonyl content were significantly increased, but LINE‐1 methylation was significantly decreased in the H₂O₂‐treated cells. LINE‐1 methylation was restored by TA, NAC, methionine, SAM and folic acid. SAM level in H₂O₂‐treated cells was significantly decreased, while total glutathione was significantly increased. SAM level in H₂O₂‐treated cells was restored by NAC, methionine, SAM and folic acid; while, total glutathione level was normalized by TA and NAC. Hcy was significantly decreased in the H₂O₂‐treated cells and subsequently restored by NAC. In conclusion, in bladder cancer and normal kidney cells exposed to H₂O₂, SAM and Hcy were decreased, but total glutathione was increased. Treatments with antioxidants (TA and NAC) and one‐carbon metabolites (SAM, methionine and folic acid) restored these changes. This pioneer finding suggests that exposure of cells to ROS activates glutathione synthesis via the transsulfuration pathway leading to deficiency of Hcy, which consequently causes SAM depletion and eventual hypomethylation of LINE‐1. Copyright © 2015 John Wiley & Sons, Ltd.     

Flavin oxidation in flavin‐dependent N‐monooxygenases

Siderophore A (SidA) from Aspergillus fumigatus is a flavin‐containing monooxygenase that hydroxylates ornithine (Orn) at the amino group of the side chain. Lysine (Lys) also binds to the active site of SidA; however, hydroxylation is not efficient and H₂O₂ is the main product. The effect of pH on steady‐state kinetic parameters was measured and the results were consistent with Orn binding with the side chain amino group in the neutral form. From the pH dependence on flavin oxidation in the absence of Orn, a pK_a value >9 was determined and assigned to the FAD‐N5 atom. In the presence of Orn, the pH dependence displayed a pK_a value of 6.7 ±0.1 and of 7.70 ±0.10 in the presence of Lys. Q102 interacts with NADPH and, upon mutation to alanine, leads to destabilization of the C4a‐hydroperoxyflavin (FAD_OOH). Flavin oxidation with Q102A showed a pK_a value of ~8.0. The data are consistent with the pK_a of the FAD N5‐atom being modulated to a value >9 in the absence of Orn, which aids in the stabilization of FAD_OOH. Changes in the FAD‐N5 environment lead to a decrease in the pK_a value, which facilitates elimination of H₂O₂ or H₂O. These findings are supported by solvent kinetic isotope effect experiments, which show that proton transfer from the FAD N5‐atom is rate limiting in the absence of a substrate, however, is significantly less rate limiting in the presence of Orn and or Lys.     

Shear stress‐mediated F1/FO ATP synthase‐dependent CO2 gas excretion from human pulmonary arteriolar endothelial cells

We studied the physiological role of flow through pulmonary arterioles in CO₂ gas exchange. We established human pulmonary arteriolar endothelial cells (HPAoEC). The cells demonstrated marked immunocytochemical staining of PECAM‐1, VEGF R2, ACE‐1, and CA type IV on their cell surface. Ten seconds shear stress stimulation caused the co‐release of H⁺ and ATP via the activation of F₁/F_O ATP synthase on the HPAoEC. F₁/F_O ATP synthase was immunocytochemically observed on the cell surface of non‐permeabilized HPAoEC. In the shear stress‐loaded HPAoEC culture media supernatant, ATPase activity increased in a time‐dependent manner. The HPAoEC were strongly stained for NTPDase 1, which partially co‐localized with purinergic P2Y1. The purinergic P2Y1 receptor agonist UTP (10^?6 M) significantly potentiated the shear stress‐induced increase in ATPase activity in the culture medium supernatant. Ten seconds shear stress stimulation also produced stress strength‐dependent CO₂ gas excretion from the HPAoEC, which was significantly reduced by the inhibition of F₁/F_O ATP synthase or CA IV on the endothelial cell (EC) surface. In conclusion, we have proposed a new concept of CO₂ exchange in the human lung, flow‐mediated F₁/F_O ATP synthase‐dependent H⁺ secretion, resulting in the facilitation of a dehydration reaction involving in plasma and the excretion of CO₂ gas from arteriolar ECs. J. Cell. Physiol. 227: 2059–2068, 2012. © 2011 Wiley Periodicals, Inc.     

F1FO ATP Synthase Is Expressed at the Surface of Embryonic Rat Heart‐Derived H9c2 Cells and Is Affected by Cardiac‐Like Differentiation

Taking advantage from the peculiar features of the embryonic rat heart‐derived myoblast cell line H9c2, the present study is the first to provide evidence for the expression of F₁F_O ATP synthase and of ATPase Inhibitory Factor 1 (IF₁) on the surface of cells of cardiac origin, together documenting that they were affected through cardiac‐like differentiation. Subunits of both the catalytic F₁ sector of the complex (ATP synthase‐β) and of the peripheral stalk, responsible for the correct F₁‐F_O assembly/coupling, (OSCP, b, F6) were detected by immunofluorescence, together with IF₁. The expression of ATP synthase‐β, ATP synthase‐b and F6 were similar for parental and differentiated H9c2, while the levels of OSCP increased noticeably in differentiated cells, where the results of in situ Proximity Ligation Assay were consistent with OSCP interaction within ecto‐F₁F_O complexes. An opposite trend was shown by IF₁ whose ectopic expression appeared greater in the parental H9c2. Here, evidence for the IF₁ interaction with ecto‐F₁F_O complexes was provided. Functional analyses corroborate both sets of data. i) An F₁F_O ATP synthase contribution to the exATP production by differentiated cells suggests an augmented expression of holo‐F₁F_O ATP synthase on plasma membrane, in line with the increase of OSCP expression and interaction considered as a requirement for favoring the F₁‐F_O coupling. ii) The absence of exATP generation by the enzyme, and the finding that exATP hydrolysis was largely oligomycin‐insensitive, are in line in parental cells with the deficit of OSCP and suggest the occurrence of sub‐assemblies together evoking more regulation by IF₁. J. Cell. Biochem. 9999: 1–13, 2015. © 2015 Wiley Periodicals, Inc. J. Cell. Biochem. 117: 470–482, 2016. © 2015 Wiley Periodicals, Inc.     

Coproporphyrin III excretion identifies the anaerobic coproporphyrinogen III oxidase HemN as a copper target in the Cu+‐ATPase mutant copA− of Rubrivivax gelatinosus

Two genes encoding structurally similar Copper P_1B‐type ATPases can be identified in several genomes. Notwithstanding the high sequence and structural similarities these ATPases held, it has been suggested that they fulfil distinct physiological roles. In deed, we have shown that the Cu⁺‐ATPase CtpA is required only for the activity of cuproproteins in the purple bacterium Rubrivivax gelatinosus; herein, we show that CopA is not directly required for cytochrome c oxidase but is vital for copper tolerance. Interestingly, excess copper in the copA^? mutant resulted in a substantial decrease of the cytochrome c oxidase and the photosystem under microaerobic and anaerobic conditions together with the extrusion of coproporphyrin III. The data indicated that copper targeted the tetrapyrrole biosynthesis pathway at the level of the coproporphyrinogen III oxidase HemN and thereby affects the oxidase and the photosystem. This is the first in vivo demonstration that copper, like oxygen, affects tetrapyrrole biosynthesis presumably at the level of the SAM and [4Fe‐4S] containing HemN enzyme. In light of these results and similar findings in Escherichia coli, the potential role of copper ions in the evolution of [4Fe‐4S] enzymes and the Cu⁺‐ATPases is discussed.     

Ellagic acid mitigates arsenic‐trioxide‐induced mitochondrial dysfunction and cytotoxicity in SH‐SY5Y cells

In the current study, neuroprotective significance of ellagic acid (EA, a polyohenol) was explored by primarily studying its antioxidant and antiapoptotic potential against arsenic trioxide (As₂O₃)‐induced toxicity in SH‐SY5Y human neuroblastoma cell lines. The mitigatory effects of EA with particular reference to cell viability and cytotoxicity, the generation of reactive oxygen species, DNA damage, and mitochondrial dynamics were studied. Pretreatment of SH‐SY5Y cells with EA (10 and 20 μM) for 60 min followed by exposure to 2 μM As₂O₃ protected the SH‐SY5Y cells against the harmful effects of the second. Also, EA pre‐treated groups expressed improved viability, repaired DNA, reduced free radical generation, and maintained altered mitochondrial membrane potential than those exposed to As₂O₃ alone. EA supplementation also inhibited As₂O₃‐induced cytochrome c expression that is an important hallmark for determining mitochondrial dynamics. Thus, the current investigations are more convinced for EA as a promising candidate in modulating As₂O₃‐induced mitochondria‐mediated neuronal toxicity under in vitro system.     

Mixtures of hemoglobin‐based oxygen carriers and perfluorocarbons exhibit a synergistic effect in oxygenating hepatic hollow fiber bioreactors

Hepatic hollow fiber (HF) bioreactors are being developed for use as bioartificial liver assist devices (BLADs). In general, BLADs suffer from O₂ limited transport, which reduces their performance. This modeling study seeks to investigate if O₂ carrying solutions consisting of mixtures of hemoglobin‐based oxygen carriers (HBOCs) and perfluorocarbons (PFCs) can enhance O₂ transport to hepatocytes cultured in the extra capillary space (ECS) of HF bioreactors. We simulated supplementing the circulating cell culture media stream of the HF bioreactor with a mixture containing these two types of oxygen carriers (HBOCs and PFCs). A mathematical model was developed based on the dimensions and physical characteristics of a commercial HF bioreactor. The resulting set of partial differential equations, which describes fluid transport; as well as, mass transport of dissolved O₂ in the pseudo‐homogeneous PFC/water phase and oxygenated HBOC, was solved to yield the O₂ concentration field in the three HF domains (lumen, membrane and ECS). Our results show that mixtures of HBOC and PFC display a synergistic effect in oxygenating the ECS. Therefore, the presence of both HBOC and PFC in the circulating cell culture media dramatically improves transport of O₂ to cultured hepatocytes. Moreover, the in vivo O₂ spectrum in a liver sinusoid can be recapitulated by supplementing the HF bioreactor with a mixture of HBOCs and PFCs at an inlet pO₂ of 80 mmHg. Therefore, we expect that PFC‐based oxygen carriers will be more efficient at transporting O₂ at higher O₂ levels (e.g., at an inlet pO₂ of 760 mmHg, which corresponds to pure O₂ in equilibrium with aqueous cell culture media at 1 atm). Biotechnol. Bioeng. 2010; 105: 534–542. © 2009 Wiley Periodicals, Inc.     

The unique histidine in OSCP subunit of F‐ATP synthase mediates inhibition of the permeability transition pore by acidic pH

The permeability transition pore (PTP) is a Ca²⁺‐dependent mitochondrial channel whose opening causes a permeability increase in the inner membrane to ions and solutes. The most potent inhibitors are matrix protons, with channel block at pH 6.5. Inhibition is reversible, mediated by histidyl residue(s), and prevented by their carbethoxylation by diethylpyrocarbonate (DPC), but their assignment is unsolved. We show that PTP inhibition by H⁺ is mediated by the highly conserved histidyl residue (H112 in the human mature protein) of oligomycin sensitivity conferral protein (OSCP) subunit of mitochondrial F₁F_O (F)‐ATP synthase, which we also show to undergo carbethoxylation after reaction of mitochondria with DPC. Mitochondrial PTP‐dependent swelling cannot be inhibited by acidic pH in H112Q and H112Y OSCP mutants, and the corresponding megachannels (the electrophysiological counterpart of the PTP) are insensitive to inhibition by acidic pH in patch‐clamp recordings of mitoplasts. Cells harboring the H112Q and H112Y mutations are sensitized to anoxic cell death at acidic pH. These results demonstrate that PTP channel formation and its inhibition by H⁺ are mediated by the F‐ATP synthase.     

Determination of selenium via the fluorescence quenching effect of selenium on hemoglobin‐catalyzed peroxidative reaction

A new method for the determination of selenium based on its fluorescence quenching on the hemoglobin‐catalyzed reaction of H₂O₂ and l ‐tyrosine has been established. The effect of pH, foreign ions and the optimization of variables on the determination of selenium was examined. The calibration curve was found to be linear between the fluorescence quenching (F₀/F) and the concentration of selenium within the range of 0.16‐4.00 µg/mL. The detection limit was 1.96 ng/mL and the relative standard deviation was 3.14%. This method can be used for the determination of selenium in Se‐enriched garlic bulbs with satisfactory results. Copyright © 2014 John Wiley & Sons, Ltd.     

Post‐illumination transient O2‐uptake is driven by photorespiration in tobacco leaves

This study aims to elucidate the molecular mechanism for the transient increase in the O₂‐uptake rate in tobacco (Nicotiana tabacum cv Xanthi) leaves after turning off actinic lights (ALs). The photosynthetic O₂ evolution rate reaches a maximum shortly after the onset of illumination with ALs and then decreases to zero in atmospheric CO₂/O₂ conditions. After turning off the ALs, tobacco leaves show a transient increase in the O₂‐uptake rate, the post‐illumination transient O₂‐uptake, and thereafter, the O₂‐uptake rate decreases to the level of the dark‐respiration rate. Photosynthetic linear electron flow, evaluated as the quantum yield of photosystem II [Y(II)], maintained a steady‐state value distinct from the photosynthetic O₂‐evolution rate. In high‐[CO₂] conditions, the photosynthetic O₂‐evolution rate and Y(II) showed a parallel behavior, and the post‐illumination transient O₂‐uptake was suppressed. On the other hand, in maize leaves (a C4 plant), even in atmospheric CO₂/O₂ conditions, Y(II) paralleled the photosynthetic O₂‐evolution rate and the post‐illumination transient O₂‐uptake was suppressed. Hypothesizing that the post‐illumination transient O₂‐uptake is driven by C3 plant photorespiration in tobacco leaves, we calculated both the ribulose 1,5‐bisphosphate carboxylase‐ and oxygenase‐rates (Vc and Vo) from photosynthetic O₂‐evolution and the post‐illumination transient O₂‐uptake rates. These values corresponded to those estimated from simultaneous chlorophyll fluorescence/O₂‐exchange analysis. Furthermore, the H⁺‐consumption rate for ATP synthesis in both photosynthesis and photorespiration, calculated from both Vc and Vo that were estimated from chlorophyll fluorescence/CO₂‐exchange analysis, showed a positive linear relationship with the dissipation rate of the electrochromic shift signal. Thus, these findings support our hypothesis.     

Polymerization of Horseradish Peroxidase by a Laccase‐Catalyzed Tyrosine Coupling Reaction

The polymerization of proteins can create newly active and large bio‐macromolecular assemblies that exhibit unique functionalities depending on the properties of the building block proteins and the protein units in polymers. Herein, the first enzymatic polymerization of horseradish peroxidase (HRP) is reported. Recombinant HRPs fused with a tyrosine‐tag (Y‐tag) through a flexible linker at the N‐ and/or C‐termini are expressed in silkworm, Bombyx mori. Trametes sp. laccase (TL) is used to activate the tyrosine of Y‐tagged HRPs with molecular O₂ to form a tyrosyl‐free radical, which initiates the tyrosine coupling reaction between the HRP units. A covalent dityrosine linkage is also formed through a HRP‐catalyzed self‐crosslinking reaction in the presence of H₂O₂. The addition of H₂O₂ in the self‐polymerization of Y‐tagged HRPs results in lower activity of the HRP polymers, whereas TL provides site‐selectivity, mild reaction conditions and maintains the activity of the polymeric products. The cocrosslinking of Y‐tagged HRPs and HRP‐protein G (Y‐HRP‐pG) units catalyzed by TL shows a higher signal in enzyme‐linked immunosorbent assay (ELISA) than the genetically pG‐fused HRP, Y‐HRP‐pG, and its polymers. This new enzymatic polymerization of HRP promises to provide highly active and functionalized polymers for biomedical applications and diagnostics probes.     

Influence of the H‐site residue 108 on human glutathione transferase P1‐1 ligand binding: Structure‐thermodynamic relationships and thermal stability

The effect of the Y108V mutation of human glutathione S‐transferase P1‐1 (hGST P1‐1) on the binding of the diuretic drug ethacrynic acid (EA) and its glutathione conjugate (EASG) was investigated by calorimetric, spectrofluorimetric, and crystallographic studies. The mutation Tyr 108 → Val resulted in a 3D‐structure very similar to the wild type (wt) enzyme, where both the hydrophobic ligand binding site (H‐site) and glutathione binding site (G‐site) are unchanged except for the mutation itself. However, due to a slight increase in the hydrophobicity of the H‐site, as a consequence of the mutation, an increase in the entropy was observed. The Y108V mutation does not affect the affinity of EASG for the enzyme, which has a higher affinity (K_d ～ 0.5 μM) when compared with those of the parent compounds, K ～ 13 μM, K ～ 25 μM. The EA moiety of the conjugate binds in the H‐site of Y108V mutant in a fashion completely different to those observed in the crystal structures of the EA or EASG wt complex structures. We further demonstrate that the ΔC_p values of binding can also be correlated with the potential stacking interactions between ligand and residues located in the binding sites as predicted from crystal structures. Moreover, the mutation does not significantly affect the global stability of the enzyme. Our results demonstrate that calorimetric measurements maybe useful in determining the preference of binding (the binding mode) for a drug to a specific site of the enzyme, even in the absence of structural information.     

Differential responses in two varieties of winter wheat to elevated ozone concentration under fully open‐air field conditions

Two modern cultivars [Yangmai16 (Y16) and Yangfumai 2 (Y2)] of winter wheat (Triticum aestivum L.) with almost identical phenology were investigated to determine the impacts of elevated ozone concentration (E‐O₃) on physiological characters related to photosynthesis under fully open‐air field conditions in China. The plants were exposed from the initiation of tillering to final harvest, with E‐O₃ of 127% of the ambient ozone concentration (A‐O₃). Measurements of pigments, gas exchange rates, chlorophyll a fluorescence and lipid oxidation were made in three replicated plots throughout flag leaf development. In cultivar Y2, E‐O₃ significantly accelerated leaf senescence, as indicated by increased lipid oxidation as well as faster declines in pigment amounts and photosynthetic rates. The lower photosynthetic rates were mainly due to nonstomatal factors, e.g. lower maximum carboxylation capacity, electron transport rates and light energy distribution. In cultivar Y16, by contrast, the effects of E‐O₃ were observed only at the very last stage of flag leaf ageing. Since the two cultivars had almost identical phenology and very similar leaf stomatal conductance before senescence, the greater impacts of E‐O₃ on cultivars Y2 than Y16 cannot be explained by differential ozone uptake. Our findings will be useful for scientists to select O₃‐tolerant wheat cultivars against the rising surface [O₃] in East and South Asia.     

Enhancement of the hydrolysis activity of F0F1‐ATPases using 60 Hz magnetic fields

The effects of extremely low frequency (ELF) magnetic fields on membrane F₀F₁‐ATPase activity have been studied. When the F₀F₁‐ATPase was exposed to 60 Hz magnetic fields of different magnetic intensities, 0.3 and 0.5 mT magnetic fields enhanced the hydrolysis activity, whereas 0.1 mT exposure caused no significant changes. Even if the F₀F₁‐ATPase was inhibited by N,N‐dicyclohexylcarbodiimide, its hydrolysis activity was enhanced by a 0.5 mT 60 Hz magnetic field. Moreover, when the chromatophores which were labeled with F‐DHPE were exposed to a 0.5 mT, 60 Hz magnetic field, it was found that the pH of the outer membrane of the chromatophore was unchanged, which suggested that the magnetic fields used in this work did not affect the activity of F0. Taken together, our results show that the effects of magnetic fields on the hydrolysis activity of the membrane F₀F₁‐ATPases were dependent on magnetic intensity and the threshold intensity is between 0.1 and 0.3 mT, and suggested that the F1 part of F₀F₁‐ATPase may be an end‐point affected by magnetic fields. Bioelectromagnetics 30:663–668, 2009. © 2009 Wiley‐Liss, Inc.     

Antioxidant enzyme activities and hormonal status in response to Cd stress in the wetland halophyte Kosteletzkya virginica under saline conditions

Salt marshes constitute major sinks for heavy metal accumulation but the precise impact of salinity on heavy metal toxicity for halophyte plant species remains largely unknown. Young seedlings of Kosteletzkya virginica were exposed during 3 weeks in nutrient solution to Cd 5 µM in the presence or absence of 50 mM NaCl. Cadmium (Cd) reduced growth and shoot water content and had major detrimental effect on maximum quantum efficiency (F_v/F_m), effective quantum yield of photosystem II (Y(II)) and electron transport rates (ETRs). Cd induced an oxidative stress in relation to an increase in O₂^?? and H₂O₂ concentration and lead to a decrease in endogenous glutathione (GSH) and α‐tocopherol in the leaves. Cd not only increased leaf zeatin and zeatin riboside concentration but also increased the senescing compounds 1‐aminocyclopropane‐1‐carboxylic acid (ACC) and abscisic acid (ABA). Salinity reduced Cd accumulation already after 1 week of stress but was unable to restore shoot growth and thus did not induce any dilution effect. Salinity delayed the Cd‐induced leaf senescence: NaCl reduced the deleterious impact of Cd on photosynthesis apparatus through an improvement of F_v/F_m, Y(II) and ETR. Salt reduced oxidative stress in Cd‐treated plants through an increase in GSH, α‐tocopherol and ascorbic acid synthesis and an increase in glutathione reductase (EC 1.6.4.2) activity. Additional salt reduced ACC and ABA accumulation in Cd+NaCl‐treated leaves comparing to Cd alone. It is concluded that salinity affords efficient protection against Cd to the halophyte species K. virginica, in relation to an improved management of oxidative stress and hormonal status.     

Sol‐gel synthesis and luminescent properties of red‐emitting Y(P,V)O4:Eu3+ phosphors

Eu³⁺‐activated Y(P,V)O₄ phosphors were prepared by the EDTA sol‐gel method, and the corresponding morphologies and luminescent properties were investigated. The sample particles were relatively spheroid with size of 2–3 µm and had a smooth surface. The excitation spectra for Y(P,V)O₄:Eu³⁺ consisted of three strong excitation bands in the 200–350 nm range, which were attributed to a Eu³⁺‐ O^2? charge‐transfer band and ¹A₁?¹ T₁/¹ T₂ transitions in VO₄^3?. The as‐synthesized phosphors exhibited a highly efficient red luminescence at 613 nm due to the Eu^{3+ 5}D₀?⁷ F₂ electric dipole transition. With the increase in the V⁵⁺/P⁵⁺ ratio, the luminescence intensity of the red phosphor under UV excitation was greatly improved due to enhanced VO₄^3? → Eu³⁺ energy transfer. Copyright © 2015 John Wiley & Sons, Ltd.     

Structural,morphological and steady state photoluminescence spectroscopy studies of red Eu3+‐doped Y2O3 nanophosphors prepared by the sol‐gel method

Europium trivalent (Eu³⁺)‐doped Y₂O₃ nanopowders of different concentrations (0.5, 2.5, 5 or 7 at.%) were synthesized by the sol‐gel method, at different pH values (pH 2, 5 or 8) and annealing temperatures (600°C, 800°C or 1000°C). The nanopowders samples were characterized by X‐ray diffraction (XRD), field emission scanning electron microscopy (FE‐SEM), Fourier transform infrared spectroscopy (FT‐IR) and steady state photoluminescence spectroscopy. The effect of pH of solution and annealing temperatures on structural, morphological and photoluminescence properties of Eu³⁺‐doped Y₂O₃ were studied and are discussed. It was found that the average crystallite size of the nanopowders increased with increasing pH and annealing temperature values. The Y₂O₃:Eu³⁺ material presented different morphology and its evolution depended on the pH value and the annealing temperature. Activation energies at different pH values were determined and are discussed. Under ultraviolet (UV) light excitation, Y₂O₃:Eu³⁺ showed narrow emission peaks corresponding to the ⁵D_0–⁷F_J (J = 0, 1, 2 and 3) transitions of the Eu³⁺ ion, with the most intense red emission at 611 assigned to forced electric dipole ⁵D₀→⁷F₂. The emission intensity became more intense with increasing annealing temperature and pH values, related to the improvement of crystalline quality. For the 1000°C annealing temperature, the emission intensity presented a maximum at pH 5 related to the uniform cubic‐shaped particles. It was found that for lower annealing temperatures (small crystallite size) the CTB (charge transfer band) position presented a red shift. Copyright © 2015 John Wiley & Sons, Ltd.