Purification and Characterization of Thermostable α-Galactosidase from <Emphasis Type="Italic">Aspergillus terreus</Emphasis><Subscript>GR</Subscript>

An extracellular thermostable α-galactosidase producing Aspergillus terreus _GR strain was isolated from soil sample using guar gum as sole source of carbon. It was purified to apparent homogeneity by acetone precipitation, gel filtration followed by DEAE-Sephacel chromatographic step. The purified enzyme showed a single band after sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE). The molecular weight of the purified enzyme after SDS-PAGE was 108 kDa. The enzyme showed optimum pH and temperature of 5.0 and 65 °C, respectively, for artificial substrate pNPαGal. α-Galactosidase from A. terreus _GR is found to be thermostable, as it was not inactivated after heating at 65 °C for 40 min. The K _m for pNPαGal, oNPαGal, raffinose, and stachyose are 0.1, 0.28, 0.42, and 0.33 mM, respectively. Inhibitors such as 1,10-phenanthroline, phenylmethylsulfonyl fluoride, ethylenediaminetetraacetic acid, mercaptoethanol, and urea have no effect, whereas N-bromosuccinamide inhibited enzyme activity by 100%. Among metal ions tested, Mg²⁺, Ni²⁺, Ca²⁺, Co²⁺, and Mn²⁺ had no effect on enzyme activity, but Ag⁺, Hg²⁺, and Cu²⁺ have inhibited complete activity.     

Investigation of metal activation of a partially purified polyphenol oxidase enzyme electrode

Biosensors can be developed using different biological materials and immobilization technologies. Enzymes are generally used in biosensor construction, and some enzymes need metal ions or small organic molecules as a cofactor for their activation. Polyphenol oxidases can be activated by several metal ions such as Cu²⁺, Mg²⁺, Zn²⁺, Mn²⁺, and Ni²⁺. In this study, a new measurement method has been developed that is based on the metal ion activation of the polyphenol oxidase enzyme used in the biosensor preparation, especially to determine the concentration of Mg²⁺ ions. Polyphenol oxidase (PPO) (EC 1.10.3.1) was partially purified from potato (Solanum tuberosum) by using (NH₄)₂SO₄ precipitation, dialysis, and lyophylization processes. As a result of this processes, approximately 30-fold purification was achieved for PPO. For construction of the biosensor, the enzyme was immobilized on the dissolved oxygen probe membrane using gelatin and glutaraldehyde (2.5%). Using the biosensor, we obtained responses for catechol in the absence and presence of Mg²⁺ ions. Differences between the biosensor responses were related to the concentration of Mg²⁺ ions. The biosensor response depends linearly on concentration of Mg²⁺ ions between 0.05 and 7.5?mM. In the optimization studies, phosphate buffer (pH 7.0, 50?mM) and 35°C were determined to be the optimum conditions. This project will be a novel biosensor study and it might bring a new term, ‘activation based biosensor’ into the biosensor area.     

Study of Complex Formation between N-Phenylaza-15-Crown-5 with Mg2+, Ca2+, Ag+ and Cd2+ Metal Cations in Some Binary Mixed Aqueous and Non-aqueous Solvents using the Conductometric Method

The complexation reactions between Mg²⁺, Ca²⁺, Ag⁺ and Cd²⁺ metal cations with N-phenylaza-15-crown-5 (Ph-N15C5) were studied in acetonitrile (AN)–methanol (MeOH), methanol (MeOH)–water (H₂O) and propanol (PrOH)–water (H₂O) binary mixtures at different temperatures using the conductometric method. The conductance data show that the stochiometry of all of the complexes with Mg²⁺, Ca²⁺, Ag⁺ and Cd²⁺ cations is 1:1 (L:M). The stability of the complexes is sensitive to the solvent composition and a non-linear behaviour was observed for variation of log K _f of the complexes versus the composition of the binary mixed solvents. The selectivity order of Ph-N15C5 for the metal cations in neat MeOH is Ag⁺>Cd²⁺>Ca²⁺>Mg²⁺, but in the case of neat AN is Ca²⁺>Cd²⁺>Mg²⁺>Ag⁺. The values of thermodynamic parameters (ΔH _c ^o , ΔS _c ^o ) for formation of Ph-N15C5–Mg²⁺, Ph-N15C5–Ca²⁺, Ph-N15C5–Ag⁺ and Ph-N15C5–Cd²⁺ complexes were obtained from temperature dependence of stability constants and the results show that the thermodynamics of complexation reactions is affected by the nature and composition of the mixed solvents.     

Solvent extraction of magnesium, zinc and manganese into nitrobenzene by using strontium dicarbollylcobaltate in the presence of valinomycin

From extraction experiments and γ-activity measurements, the exchange extraction constants corresponding to the general equilibrium M²⁺(aq)+SrL²⁺(nb)⇔ML²⁺(nb)+Sr²⁺(aq) taking place in the two-phase water-nitrobenzene system (M²⁺ = Mg²⁺, Zn²⁺, Mn²⁺; L = valinomycin; aq = aqueous phase, nb = nitrobenzene phase) were evaluated. Further, the stability constants of the ML²⁺ complexes in water saturated nitrobenzene were calculated. They were found to increase in the order of Mg²⁺<Mn²⁺<Zn²⁺.     

Characterization of Cyclodextrin Glucanotransferase Produced by <Emphasis Type="Italic">Bacillus megaterium</Emphasis>

Cyclodextrin glucanotransferase, produced by Bacillus megaterium, was characterized, and the biochemical properties of the purified enzyme were determined. The substrate specificity of the enzyme was tested with different α-1,4-glucans. Cyclodextrin glucanotransferase displayed maximum activity in the case of soluble starch, with a K _m value of 3.4 g/L. The optimal pH and temperature values for the cyclization reaction were 7.2 and 60 °C, respectively. The enzyme was stable at pH 6.0–10.5 and 30 °C. The enzyme activity was activated by Sr²⁺, Mg²⁺, Co²⁺, Mn²⁺, and Cu²⁺, and it was inhibited by Zn²⁺and Ag⁺. The molecular mass of cyclodextrin glucanotransferase was established to be 73,400 Da by sodium dodecyl sulfate–polyacrylamide gel electrophoresis, 68,200 Da by gel chromatography, and 75,000 Da by mass spectrometry. The monomer form of the enzyme was confirmed by the analysis of the N-terminal amino acid sequence. Cyclodextrin glucanotransferase formed all three types of cyclodextrins, but the predominant product was β-cyclodextrin.     

Purification and Characterization of a Hyperthermostable and High Maltogenic α-Amylase of an Extreme Thermophile <Emphasis Type="Italic">Geobacillus thermoleovorans</Emphasis>

The purified α-amylase of Geobacillus thermoleovorans had a molecular mass of 26 kDa with a pI of 5.4, and it was optimally active at 100 °C and pH 8.0. The T _1/2 of α-amylase at 100 °C increased from 3.6 to 5.6 h in the presence of cholic acid. The activation energy and temperature quotient (Q ₁₀) of the enzyme were 84.10 kJ/mol and 1.31, respectively. The activity of the enzyme was enhanced strongly by Co²⁺ and Fe²⁺; enhanced slightly by Ba²⁺, Mn²⁺, Ni²⁺, and Mg²⁺; inhibited strongly by Sn²⁺, Hg²⁺, and Pb²⁺, and inhibited slightly by EDTA, phenyl methyl sulfonyl fluoride, N-ethylmaleimide, and dithiothreitol. The enzyme activity was not affected by Ca²⁺ and ethylene glycol-bis (β-amino ethyl ether)-N,N,N,N-tetra acetic acid. Among different additives and detergents, polyethylene glycol 8000 and Tween 20, 40, and 80 stabilized the enzyme activity, whereas Triton X-100, glycerol, glycine, dextrin, and sodium dodecyl sulfate inhibited to a varied extent. α-Amylase exhibited activity on several starch substrates and their derivatives. The K _m and K _cat values (soluble starch) were 1.10 mg/ml and 5.9 × 10³ /min, respectively. The enzyme hydrolyzed raw starch of pearl millet (Pennisetum typhoides) efficiently.     

Purification, characterization, kinetic properties, and thermal behavior of extracellular polygalacturonase produced by filamentous fungus Tetracoccosporium sp

For the first time, a polygalacturonase from the culture broth of Tetracoccosporium sp. was isolated and incubated at 30°C in an orbital shaker at 160 rpm for 48h. The enzyme was purified by ammonium sulfate precipitation and two-step ion-exchange chromatography and had an apparent molecular mass of 36 kDa, as shown by sodium dodecyl sulfate (SDS)-polyacrylamide gel electrophoresis. Its optimum activity was at pH 4.3 and 40°C, and the K _m and V _max values of this enzyme (for polygalacturonic acid) were 3.23 mg/mL and 0.15 μmol/min, respectively. Ag⁺, Co²⁺, EDTA, Tween-20, Tween-80, and Triton X-100 stimulated polygalacturonase activity whereas Al³⁺, Ba²⁺, Ca²⁺, Fe²⁺, Fe³⁺, Ni²⁺, Mg²⁺, Mn²⁺, and SDS inhibited it. In addition, iodoacetamide and iodoacetic acid did not inhibit enzyme activity at a concentration of 1 mM, indicating that cysteine residues are not part of the catalytic site of polygalacturonase. We studied the kinetic properties and thermal inactivation of polygalacturonase. This enzyme exhibited a t _1/2 of 63 min at 60°C and its specific activity, turnover number, and catalytic efficiency were 6.17 U/mg, 113.64 min⁻¹, and 35.18 mL/(min·mg), respectively. The activation energy (ΔE ^#) for heat inactivation was 5.341 kJ/mol, and the thermodynamic activation parameters ΔG ^#, ΔH ^#, and ΔS ^# were also calculated, revealing a potential application for the industry.     

phosphate hydrate complexes of singly and doubly charged magnesium ions: Structure,energies, and spin states

For mixed magnesium phosphate hydrate complexes containing Mg²⁺ and Mg⁺ cations and HPO₄²⁻, HPO₄⁻, and H₂P₂O₇²⁻ anions, theoretical analysis of the electronic structure and energies has been performed at the model level in order to predict the actual role of these systems in various reactions that occur in the catalytic sites of ATP synthesizing enzymes. The calculations (DFT/B3LYP, MP2 with the 6–31G* basis set) of isolated aqua complexes Mg(H₂O) _n ^p (n = 1−6, p = 0, +1, +2) show that their relative stability monotonically increases with increasing n in each series and sharply decreases at a given n in going from the charged systems of Mg²⁺ (4–16 eV) and Mg⁺ (2–7 eV) to the neutral systems of Mg (<2 eV). An even higher stability is predicted for mixed magnesium complexes. The energies of fragmentation of mixed Mg²⁺ complexes into singlet phosphate and Mg²⁺-containing fragments at n = 0–4 are within 6–27 eV, and the energies of fragmentation into the corresponding radical ions are within 3–10 eV; for the Mg⁺ complexes, the fragmentation energies are also high (6–14 eV). The reasons for the enhanced stability of the complexes of both types have been analyzed with allowance for the predicted specific features of the electron density redistribution upon complex formation. Typical changes in the geometry of the P- and Mg-containing fragments caused by formation of mixed complexes have been discussed in the framework of the vibronic model of heteroligand systems. The high stability of all mixed magnesium complexes relative to various fragmentation products presumably rules out any dissociative processes in them in the course of ATP synthesis with the participation of phosphorylating enzymes.     

Isomerization ofn-butane on the SO4/ZrO2 catalyst promoted by IV Period metals

The catalytic activity of superacidic systems based on SO₄/ZrO₂ and modified by IV Period metals in isomerization ofn-butane was studied. At low temperatures of the reaction, the introduction of Fe³⁺, Sc³⁺, Co²⁺, or Zn²⁺ ions (1%) increases the yield of isobutane by 1.5 times due to the activation ofn-butane on the sites created by the promoting ions. The addition of Cr³⁺, V⁴⁺, or Mn²⁺ (1%) decreases the catalytic activity because of a decrease in the catalyst acidity, most likely, due to the reduction of surface sulfur species. The influence of the nature of the support and surface additives of SiO₂, TiO₂, and ZrO₂ on the activity and selectivity of the catalytic system inn-butane isomerization was studied. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7 pp. 1276–1280, July, 1999     

A Simple Fluorometric Method Using Chlorophyll a for Determination of Hg2+ Ion

A simple and green analytical procedure based on chlorophyll a is presented for the determination of Hg²⁺ ion. Chlorophyll a was extracted and purified from the leaves of pea and is employed as a reagent for analysis of Hg²⁺ ion. It displays remarkable fluorescence emission at 674 nm when excited at 412 nm. The emission intensity decreased significantly on exposure to various concentrations of Hg²⁺ ion. This forms the basis for the determination of Hg²⁺ ion. The proposed method was evaluated for sensitivity and selectivity. The linear concentration range was found to be 2.0–10 μM with r² = 0.997 and the limit of detection for Hg²⁺ ion was 1.3 μM. Ions including Pb²⁺, Cd²⁺, Ag⁺, Zn²⁺, Co²⁺, Ni²⁺, Cu²⁺, Mg²⁺, Mn²⁺, Ru³⁺, Er³⁺, K⁺, Na⁺, NH₄⁺, Cl⁻, NO₃⁻, CH₃COO⁻ and SO₄²⁻ did not interfere with the measurement of Hg²⁺ ion even at 500-fold excess. Since chlorophyll a is widely available in the leaves of most plants, and the extraction and purification process is simple, this technique can provide an alternative, sensitive and economical way to determine Hg²⁺ ion.     

Determination of alkali, alkaline earth and transition metal ions in UO2, ThO2 powders and sintered (Th,U)O2 pellets by ion chromatography

An ion chromatographic method has been developed for the determination of traces of Li⁺, Na⁺, K⁺, Ca²⁺, Mg²⁺, Sr²⁺, Fe³⁺, Cu²⁺, Ni^2+, Co²⁺, Zn²⁺, Cd²⁺, Mn²⁺ in UO₂, ThO₂ powders and sintered (Th,U)O₂ pellets. This new method utilizes poly-(butadiene-maleic acid) (PBDMA) coated silica cation exchange column and mixed functionality column of anion and cation exchange to achieve the separation of alkali, alkaline earths and transition metal ions, respectively. It involves matrix separation after sample dissolution by solvent extraction with TBP (tri butyl phosphate)-TOPO (tri octyl phosphine oxide)/CCl₄. Interference of transition metal ions in the determination of alkali, alkaline earth metal ions are removed by using pyridine 2,6-dicarboxylic acid (PDCA) in the tartaric acid mobile phase. Mobile phase composition is optimized for the base line separation of alkali, alkaline earth and transition metal ions. Linear calibration graphs in the range 0.01–20 μg mL⁻¹ were obtained with regression coefficients better than 0.999. The respective relative standard deviations were also determined. Recoveries of the spiked samples are within ±10% of the expected value. The developed method is authenticated by comparison with certified standards of UO₂ and ThO₂ powders.     

Influence of MgO (CaO) on the structure of silicate-phosphate glasses

Thermal and structural properties of model silicate-phosphate glasses containing the different amounts of the glass network modifiers, i.e. Mg²⁺ and Ca²⁺ were studied. To explain the changes of the parameters characterizing the glass transition effect (T_g, Δc_p) and the crystallization process (T_c, ΔH) depending on the cations modifiers additions, analysis of the bonds and chemical interactions of atoms in the structure of glasses was used. ³¹P MAS-NMR spectra of SiO₂–P₂O₅–MgO(CaO)–K₂O glasses show that the phosphate complexes are mono- and diphosphate. It has been found that increasing amounts of Mg²⁺ or Ca²⁺ cations in the structure of glasses causes the reduction of the degree of polymerization of the phosphate framework (Q¹→Q⁰). The influence of increasing of modifiers in the structure of silicate- phosphate glasses on the number of non-bridging oxygens per SiO₄ tetrahedron and density of glasses was presented.     

Stability and Structure of Binary and Ternary Metal Ion Complexes of Orotidinate 5′-Monophosphate (OMP3-) in Aqueous Solution

Abstract

The stability constants of the 1:1 complexes formed between Mg^{2 +}, Ca^{2 +}, Sr^{2 +}, Ba^{2 +}, Mn^{2 +}, Co^{2 +}, Ni^{2 +}, Cu^{2 +}, Zn ²⁺ or Cd ²⁺ and orotidinate 5′-monophosphate (OMP^3-) were determined by potentio-metric pH titrations in aqueous solution (I =0.1 M, NaNO₃; 25°C). In addition to the stability constants of these M(OMP)^? complexes, for several cases also the corresponding acidity constants for the release of the proton from the H(N-3) site were calculated; i.e., the formation of M(OMP-H)^2- complexes was quantified. On the basis of recent measurements for simple phosphate monoesters [R-MP^2-; R is a noncoordinating residue; S.S. Massoud and H. Sigel, Inorg. Chem., 27, 1447-1453 (1988)], evidence is provided that the somewhat increased stability of all the mentioned M(OMP)^? complexes is mainly the result of a charge effect of the carboxylate group (in position 6 of OMP^3-) and not of a direct participation in complex formation; i.e., there are no indications for the formation of significant amounts of macrochelates involving the phosphate and the carboxylate groups. This is different for the M(OMP-H)^2- complexes of Co ²⁺ , Ni²⁺ and Cd²⁺: in these cases significant amounts of macrochelates form; i.e., the metal ion is not only coordinated to the phosphate group but also (in part) to the ionized ^?(N-3) site, which is placed in the neighbourhood of the phosphate residue in the dominating syn conformation of this nucleotide. For the metal ions Mg^{2 +}, Ca²⁺, Sr^{2 +}, Ba²⁺ and Mn^{2 +}, which have in general a rather low affinity for N binding sites, no evidence for the formation of macrochelates is detected. In addition, the stability constants of the ternary Cu(Arm)(OMP)^? complexes, where Arm = 2,2′-bipyridyl or 1,10-phenanthroline, were determined by potentiometric pH titrations. Evaluation of the stability data shows that an equilibrium betweeen an ‘open’ isomer and a Cu(Arm)(OMP)^? species with an intramolecular stack exists; the formation degree of these aromatic ring stacks reaches about 40 percent. Overall it is quite evident that OMP^3- is a versatile ligand with remarkable properties which may be utilized by nature in recognition reactions during the intricate metabolic processes in which this nucleotide is involved.     

Purification and Biochemical Characterization of Polyphenol Oxidases from Embryogenic and Nonembryogenic Cotton (<Emphasis Type="Italic">Gossypium hirsutum</Emphasis> L.) Cells

Polyphenol oxidases (PPOs) were isolated from cell suspensions of two cultivars of cotton (Gossypium hirsutum L.), and their biochemical characteristics were studied. PPO from Coker 312, an embryogenic cultivar, showed a highest affinity to catechol 20 mM, and PPO from R405-2000, a nonembryogenic cultivar, showed a highest affinity to 4-methylcatechol 20 mM. The optimal pH for PPO activity was 7.0 and 6.0 for Coker 312 and R405-2000, respectively. The enzyme had an optimal temperature of 25 °C and was relatively stable at 20–30 °C. Reducing sodium metabisulfite, ascorbic acid, dithiothreitol, SnCl₂, and FeCl₃ markedly inhibited PPO activity, whereas its activity was highly enhanced by Mg²⁺, Ca²⁺, and Mn²⁺ and was moderately inhibited by Ba²⁺, Cu²⁺, and Zn²⁺. The analysis revealed a single band on the sodium dodecyl sulfate polyacrylamide gel electrophoresis which corresponded to a molecular weight of 55 kDa for Coker 312 and 42 kDa for R405-2000.     

A SPECTRAL STUDY OF Cu2+ AND Cd2+ WITH A SUBSTITUTED PYRAZINE LIGAND

Abstract

We wish to report a novel ligand that forms an intense blue to purple color when complexed with various non-transition as well as transition metals. This color appears when Cd²⁺, Zn²⁺, Ag¹⁺, Mg²⁺ Fe²⁺, Fe³⁺, Cu²⁺, Co²⁺, Ni²⁺, or Mn²⁺ is added to N,N′-bis(4-N″,N″-dimethylanilinyl)-2,5-bis(methylenimino)pyrazine (Figure 1) which is dissolved in dimethylformamide (DMF). The ligand is capable of being multidentate; therefore, spectro-photometric titration experiments were performed using Cd²⁺ in one experiment and Cu²⁺ in another experiment. If these ions can be considered as being representative of the non-transition and transition complexes respectively, then the stoichiometry is 1:1 and 2:1 (metal:ligand). Whether this sampling is truly representative is under further investigation.     

Grass Degrading β-1,3-1,4-d-glucanases from Bacillus subtilis GN156: Purification and Characterization of Glucanase J1 and pJ2 Possessing Extremely Acidic pI

Purification of β-1,3-1,4-glucanase from the cell-free culture fluid of Bacillus subtilis GN156 by affinity chromatography of epoxy-activated sepharose 6B and ultrafiltration technique resulted in homogeneous J1 and partially purified pJ2 enzymes. The molecular weight and pI of J1 were 25 kDa and 3.5, respectively, while those for J2 were 90 kDa and 3.6, respectively. Both β-1,3-1,4-glucanase J1 and pJ2 had optimum pH values of 6–6.5 and an optimum temperature of 60°C. Both enzymes were not inhibited by Li²⁺ but were inhibited significantly by Ca²⁺, Cu²⁺, Mn²⁺ and Zn²⁺. However, J1 was slightly inhibited by Fe²⁺, while pJ2 was inhibited by Mg²⁺ as well. They were highly specific to only barley β-glucan. K _m and V _max values of J1 were 1.53 mg/ml and 8,511 μU/ml.min, respectively, while those for pJ2 were 4.36 mg/ml and 7,397 μU/ml.min, respectively. Degradation of barley β-1, 3-1,4-glucan resulted in four different oligosaccharides with 1,3 linkages triose, tetrose, pentose and a high molecular weight (HMW) with 1,3 linkage estimated from their mobilities. The quantitative degradation by the crude enzyme after of incubation yielded in descending order: triose, pentose and tetrose, while that of J1 in descending order yielded: pentose, triose and tetrose. The pJ2 showed low activity yielding a degradation pattern in descending order: pentose, triose, tetraose and a HMW polysaccharide.     

A soluble form of phosphatase in Saccharomyces cerevisiae capable of converting farnesyl diphosphate into E,E-farnesol

After anion-exchange chromatography, the soluble fraction of a cell-free extract of Saccharomyces cerevisiae showed two phosphatase activity peaks when p-nitrophenyl phosphate (pNPP) was used as the substrate. However, only the second pNPP active peak demonstrated the ability to convert farnesyl diphosphate (FPP) into E,E-farnesol. N-terminal sequence analysis of the purified pNPP/FPP phosphatase revealed that it was a truncated form of alkaline phosphatase Pho8 lacking 62 amino acids from the N-terminus and was designated Pho8Δ62. Although other isoprenyl diphosphates such as geranyl diphosphate (GPP) and geranylgeranyl diphosphate (GGPP) could also be hydrolyzed by Pho8Δ62 to the corresponding alcohols, selectivity was observed among these substrates. The optimum pH was 7.0 for all three isoprenyl diphosphate substrates. Although lower hydrolytic activity was observed for FPP and GGPP at pH 6.0 and 8.5, hydrolysis of GPP was observed only at pH 7.0. Mg²⁺ and Mn²⁺ inhibited hydrolysis of FPP and GGPP, and GGPP was more sensitive to Mg²⁺ inhibition than FPP. The rate of FPP hydrolysis increased in the presence of Triton X-100.     

Binding Interaction of Captopril with Metal Ions: A Fluorescence Quenching Study

The binding interaction of captopril (CPL) with biologically active metal ions Mg²⁺, Ca²⁺, Mn²⁺, Co²⁺, Ni²⁺, Cu²⁺ and Zn²⁺ was investigated in an aqueous acidic medium by fluorescence spectroscopy. The experimental results showed that the metal ions quenched the intrinsic fluorescence of CPL by forming CPL‐metal complexes. It was found that static quenching was the main reason for the fluorescence quenching. The quenching constant in the case of Cu²⁺ was highest among all quenchers, perhaps due to its high nuclear charge and small size. Quenching of CPL by metal ions follows the order Cu²⁺>Ni²⁺>Co²⁺>Ca²⁺>Zn²⁺>Mn²⁺>Mg²⁺. The quenching constant K_sv, bimolecular quenching constant K_q, binding constant K and the binding sites "n" were determined together with their thermodynamic parameters at 27 and 37°C. The positive entropy change indicated the gain in configurational entropy as a result of chelation. The process of interaction was spontaneous and mainly ΔS‐driven.     

Effect of copper and manganese ions on activities of laccase and peroxidases in three Pleurotus species grown on agricultural wastes

Copper (Cu²⁺) and manganese (Mn²⁺) ions influenced laccase (Lac) and peroxidase production in Pleurotus eryngii, Pleurotus ostreatus, and Pleurotus pulmonarius. In P. eryngii, the optimum Cu²⁺ concentration for Lac production was 1 mM and for peroxidases 10mM, and Mn²⁺ concentration of 5mM led to peaks of Lac and peroxidase activity. In P. ostreatus HAI 493, the highest level of Lac activity was at Cu²⁺ concentrations of 1 and 10 mM and Mn²⁺ concentration of 1mM, respectively. The absence of Cu²⁺ and Mn²⁺ caused the highest levels of peroxidase production. In P. ostreatus HAI 494, the highest level of Lac activity was at a Cu²⁺ concentration of 5 mM and at Mn²⁺ concentration of 1 mM, respectively. High levels of peroxidase activity were found in the medium without and with 1mM Cu²⁺, and at 1 and 5 mM Mn²⁺, respectively. In P. pulmonarius, the highest Lac activity was found in the presence of 5 mM Cu²⁺ and 5 mM Mn²⁺, respectively. The absence of Cu²⁺ and Mn²⁺ as well as their presence at a concentration of 1 mM led to the peaks of peroxidase activities.     

Quantum yields and quantitative spectra of firefly bioluminescence with various bivalent metal ions

We measured quantitative spectra of firefly (Photinus pyralis) bioluminescence in the presence of Zn²⁺ and other bivalent metal ions to investigate the effects of these metal ions on luciferin‐luciferase reaction. We studied the dependence of the quantum yield and spectrum on quantity and kind of bivalent metal ions. Adding various amounts of Mg²⁺, Mn²⁺ and Ca²⁺ produced virtually no change in the quantum yields or the spectra of bioluminescence. In contrast, increasing amounts of ions such as Zn²⁺ and Cd²⁺ decreased quantum yields and changed the bioluminescence color from yellow‐green to red. Quantitative analysis showed that the sensitivities of the quantum yield and color to various metal ions were in the order of Hg²⁺>Zn²⁺, Cd²⁺>Ni²⁺, Co²⁺, Fe²⁺≫Mg²⁺, Mn²⁺, Ca²⁺. We propose that the changes in quantum yield and spectrum caused by the metal ions are due to their effect on luciferase that surrounds oxyluciferin during its radioactive decay. We also found that having more metal ions accelerated bioluminescence reactions. The sensitivity of the reaction rate had no correlation with those of the quantum yield and spectrum.