Magnesium Chelation Research Articles

Rapid method for screening of both calcium and magnesium chelation with comparison of 21 known metal chelators.

Chelation is the rational treatment modality in metal overload conditions, but chelators are often non-selective and can, hence, cause an imbalance in the homeostasis of physiological metals including calcium and magnesium. The aim of this study was to develop an affordable, rapid but sensitive and precise method for determining the degree of chelation of calcium and magnesium ions and to employ this method for comparison on a panel of known metal chelators. Spectrophotometric method using o-cresolphthalein complexone (o-CC) was developed and its biological relevance was confirmed in human platelets by impedance aggregometry. The lowest detectable concentration of calcium and magnesium ions by o-CC was 2.5μM and 2μM, respectively. The indicator was stable for at least 110days. Four and seven out of twenty-one chelators strongly chelated calcium and magnesium ions, respectively. Importantly, the chelation effect of clinically used chelators was not negligible. Structure-activity relationships for eight quinolin-8-ols showed improvements in chelation particularly in the cases of dihalogen substitution, and a negative linear relationship between pKa and magnesium chelation was observed. Calcium chelation led to inhibition of platelet aggregation in concentrations corresponding to the complex formation. A novel method for screening of efficacy and safety of calcium and magnesium ion chelation was developed and validated.

Hydrogen peroxide participates in leaf senescence by inhibiting CHLI1 activity.

Hydrogen peroxide promoted leaf senescence by sulfenylating the magnesium chelating protease I subunit (CHLI1) in the chlorophyll synthesis pathway, and inhibited its activity to reduce chlorophyll synthesis. Leaf senescence is the final and crucial stage of plant growth and development, during which chlorophyll experiences varying degrees of destruction. It is well-known that the higher ROS accumulation is a key factor for leaf senescence, but whether and how ROS regulates chlorophyll synthesis in the process are unknown. Here, we report that H2O2 inhibits chlorophyll synthesis during leaf senescence via the I subunit of magnesium-chelatase (CHLI1). During leaf senescence, the decrease of chlorophyll content is accompanied by the increase of H2O2 accumulation, as well as the inhibition of catalase (CAT) genes expression. The mutant cat2-1, with increased H2O2 shows an accelerated senescence phenotype and decreased CHLI1 activity compared with the wild type. H2O2 inhibits CHLI1 activity by sulfenylating CHLI1 during leaf senescence. Consistent with this, the chli1 knockout mutant displays the same premature leaf senescence symptom as cat2-1, while overexpression of CHLI1 in cat2-1 can partially restore its early senescence phenotype. Taken together, these results illustrate that CAT2-mediated H2O2 accumulation during leaf senescence represses chlorophyll synthesis through sulfenylating CHLI1, and thus inhibits its activity, providing a new insight into the pivotal role of chlorophyll synthesis as a participant in orchestrating the leaf senescence.

Vivid COVID-19 LAMP is an ultrasensitive, quadruplexed test using LNA-modified primers and a zinc ion and 5-Br-PAPS colorimetric detection system

Sensitive and rapid point-of-care assays have been crucial in the global response to SARS-CoV-2. Loop-mediated isothermal amplification (LAMP) has emerged as an important diagnostic tool given its simplicity and minimal equipment requirements, although limitations exist regarding sensitivity and the methods used to detect reaction products. We describe the development of Vivid COVID-19 LAMP, which leverages a metallochromic detection system utilizing zinc ions and a zinc sensor, 5-Br-PAPS, to circumvent the limitations of classic detection systems dependent on pH indicators or magnesium chelators. We make important strides in improving RT-LAMP sensitivity by establishing principles for using LNA-modified LAMP primers, multiplexing, and conducting extensive optimizations of reaction parameters. To enable point-of-care testing, we introduce a rapid sample inactivation procedure without RNA extraction that is compatible with self-collected, non-invasive gargle samples. Our quadruplexed assay (targeting E, N, ORF1a, and RdRP) reliably detects 1 RNA copy/µl of sample (=8 copies/reaction) from extracted RNA and 2 RNA copies/µl of sample (=16 copies/reaction) directly from gargle samples, making it one of the most sensitive RT-LAMP tests and even comparable to RT-qPCR. Additionally, we demonstrate a self-contained, mobile version of our assay in a variety of high-throughput field testing scenarios on nearly 9,000 crude gargle samples. Vivid COVID-19 LAMP can be an important asset for the endemic phase of COVID-19 as well as preparing for future pandemics.

ХЕЛАТУВАННЯ ДВОВАЛЕНТНИХ КАТІОНІВ ТА АНТИРАКОВА АКТИВНІСТЬПОХІДНИХ 8-ГІДРОКСИСТИРИЛХІНОЛІНІВ IN VITRO

Background. The search for new methods of cancer treatment and diagnosis are important. The disadvantages of chemotherapy drugs are the rapid acquisition of resistance and high toxicity. 8-hydroxyquinoline derivatives have a wide spectrum of biological activity and have the necessary properties for fluorescent cancer diagnosis. The aim of the study was to determine the chelation of calcium, magnesium and zinc cations by hydrophobic derivatives of 8-hydroxystyrylquinolines (8HQ) 2-(4-chlorostyryl)quinolin-8-ol (STQ-Cl) and 2-(4-nitrostyryl)quinolin-8-ol (STQ-NO2) in physiological solution, the stability of the complexes and the cytotoxicity of the compounds to prostate and breast cancer cell lines in vitro. Methods. 8HQ derivatives STQ-Cl and STQ-NO2 were used. Solutions of Ca2+, Mg2+, Zn2+ cations were prepared by the method of two-fold dilutions in 0.5-0.0078125 mM concentration range based on 0.9 % NaCl. Both individual solutions of each cation and a mixture in an equivalent molar ratio were used. The concentration of 8HQ derivatives were 0.05 mM. Optical absorption was registered in 200-700 nm wavelength range. Cytotoxicity was investigated on breast (MDA-MB-231) and prostate (DU-145) cancer cell lines. STQ-Cl and STQ-NO2 derivatives in DMSO were added to the incubation solution by four-fold dilutions (0.125–0.00003 mM). For luminescence studies, MDA-MB-231 and DU-145 cells were grown on coverslips. The final concentration of 8HQ derivatives were 5 mM. Cells were kept for 5, 10, 20 and 30 min. Luminescence was recorded under the same conditions for all samples, with an exposure time of 10 ms. Results. Mg2+ and Ca2+ (0.03125 mM) were contributed to reduce the intensity of optical absorption maxima of STQ-Cl by 1.6 and 1.3 times, respectively. The effect was most pronounced at 0.015625 mM Zn2+. Weak differences in the optical absorption of solutions were detected when STQ-NO2 was incubated with different concentrations of Mg2+ and Ca2+. The optical absorption intensity of the STQ-NO2 aqueous solution was increased at 0.015625 and 0.03125 mM Zn2+. The maximum cytotoxicity against MDA-MB-231 cells for STQ-Cl was about 80 %, and STQ-NO2 was 60 % at 0.04 mM Zn2+. DU-145 cells were more sensitive to STQ-NO2 (EC50 = 0.011 mM), but weakly sensitive to STQ-Cl (50 % at 0.125 mM). The maximum luminescence intensity was after 20 min of incubation with STQ-Cl and STQ-NO2 (5 mM) for both cells lines and was not change over time. Conclusions. The decrease of optical absorption maxima of STQ-Cl aqueous solutions in the presence of magnesium, calcium, and zinc cations was a consequence of aggregation processes. This phenomenon was probably the reason for the different cytotoxicity of STQ-Cl and STQ-NO2, as well as the presence of other mechanisms of action to cancer cells. Results was a consequence of different affinity of 8-hydroxyquinoline derivatives to magnesium, calcium and zinc cations, solubility in water, stability, aggregation of metal complexes and free compounds.

Antioxidant activity analysis of collagen peptide-magnesium chelate

Antioxidant peptides from natural polymer collagen are highly desirable and their ability to coordinate with minerals will provide new leads for the prevention and treatment of oxidative stress-related diseases. Here, we tested the changes of structures and functional properties of bovine bone collagen peptides (BBCP) after magnesium chelation. The Fourier transform infrared (FTIR) results revealed that Mg(II) chelated with BBCP mainly via amino nitrogen and carboxyl oxygen atoms. The fluorescence and circular dichroism (CD) results indicated that Mg(II) could induce and stabilize the conformational structures, and change the amino acid distribution on the surfaces of BBCP. The chelation of BBCP and Mg(II) led to the improvement of radical scavenging activities, and enhanced the intracellular antioxidant enzyme activities and GSH levels, thus demonstrating higher protective and reparative effects against H2O2-induced oxidative damage. This work provides mechanistic insights for further development of peptide-magnesium chelates for oxidative stress mitigation.

Biochemical and Biophysical Characterisation of the Hepatitis E Virus Guanine-7-Methyltransferase.

Hepatitis E virus (HEV) is an understudied pathogen that causes infection through fecal contaminated drinking water and is prominently found in South Asian countries. The virus affects ~20 million people annually, leading to ~60,000 infections per year. The positive-stranded RNA genome of the HEV genotype 1 has four conserved open reading frames (ORFs), of which ORF1 encodes a polyprotein of 180 kDa in size, which is processed into four non-structural enzymes: methyltransferase (MTase), papain-like cysteine protease, RNA-dependent RNA polymerase, and RNA helicase. MTase is known to methylate guanosine triphosphate at the 5′-end of viral RNA, thereby preventing its degradation by host nucleases. In the present study, we cloned, expressed, and purified MTase spanning 33–353 amino acids of HEV genotype 1. The activity of the purified enzyme and the conformational changes were established through biochemical and biophysical studies. The binding affinity of MTase with magnesium ions (Mg2+) was studied by isothermal calorimetry (ITC), microscale thermophoresis (MST), far-UV CD analysis and, fluorescence quenching. In summary, a short stretch of nucleotides has been cloned, coding for the HEV MTase of 37 kDa, which binds Mg2+ and modulate its activity. The chelation of magnesium reversed the changes, confirming its role in enzyme activity.

Synthesis, Characterization, and Cellular Uptake of Magnesium Maltol and Ethylmaltol Complexes.

Magnesium deficiency and/or deficit (hypomagnesemia, <0.75 mmol/L in the blood) has become a recognized problem in healthcare and clinical settings. Concomitantly, supplementation has become recognized as the primary means of mitigating such deficiencies. Common magnesium supplements typically suffer from shortcomings: rapid dissociation and subsequent laxation (magnesium salts: e.g., magnesium chloride), poor water solubility (magnesium oxides and hydroxides), poor characterizability (magnesium chelates), and are/or use of non-natural ligands. To this end, there is a need for the development of fully characterized, water-soluble, all-natural magnesium compounds. Herein, we discuss the synthesis, solution and solid-state characterization, aqueous solubility, and cellular uptake of magnesium complexes of maltol and ethylmaltol, ligands whose magnesium complexes have yet to be fully explored.

Impact of the encapsulated salt characteristics on its release from multiple W/O/W emulsions

AbstractW/O/W emulsions based on Miglyol oil and stabilized by polyglycerol polyricinoleate and sodium caseinate were prepared with similar characteristics in terms of internal droplet diameter, oil globule diameter, internal aqueous fraction and fat globules fraction. The emulsions differ only by the nature of the encapsulated salt in the inner aqueous droplets. The release of each encapsulated salt from the internal to the external aqueous phase was followed during 30 days at 25°C, showing for all cases that the double structure was preserved with time and the release increased during storage, mainly according to diffusion/permeation mechanism and resulting in a competition between the chelation and the hydration enthalpy of the salt. Double emulsions encapsulating different Magnesium salts have shown that the release depends strongly on the anion via its magnesium chelation and its hydration enthalpy. Indeed, as the complexation constant of Mg2+ with its counterion increases, the leakage decreases. On the other hand, as the hydration enthalpy of Mg2+ counterion decreases, the leakage decreases too. Likewise, double emulsions encapsulating different chloride salts have shown that the release depends also on the cation via its hydration enthalpy and its chelation with caseinate affecting accordingly the stiffening of the globule/water interface, more pronounced for bivalent than for monovalent cations. It was thus directly highlighted that the release from W/O/W emulsions was well controlled by the characteristics of the salt, and anion and cation diffuse accompanied at a rate ensuring the electroneutrality of the diffusive species. These results are very useful not only in term of fundamental understanding but also on application level, especially for food supplementation such as of dairy product.Practical applicationsThe search for an innovative functional effect can lead to food supplementation with bioactive substances which can be either molecules or living bioactive cells. However, the direct addition of these substances to food can induce chemical degradation, aggregation of proteins and generate an unpleasant taste. These drawbacks can be avoided or at least reduced by encapsulation. Despite their thermodynamic instability, W/O/W emulsions are promising systems for encapsulation of hydrophilic species in their internal aqueous phase and hence find applications among others in food for taste masking or supplementation. The release of the encapsulated species to the external aqueous phase should be controlled, depending on the desired application. The release depends also on the characteristics of the encapsulated salt. A better understanding of its impact on the stability of the double emulsion will allow targeting formulation of stable emulsions and hence contributing to their better industrial development.

Chelated Magnesium Logic Gate Regulates Riboswitch Pseudoknot Formation.

Magnesium plays a critical role in the structure, dynamics, and function of RNA. The precise microscopic effect of chelated magnesium on RNA structure is yet to be explored. Magnesium is known to act through its diffuse cloud around RNA, through the outer sphere (water-mediated), inner sphere, and often chelated ion-mediated interactions. A mechanism is proposed for the role of experimentally discovered site-specific chelated magnesium ions on the conformational dynamics of SAM-I riboswitch aptamers in bacteria. This mechanism is observed with atomistic simulations performed in a physiological mixed salt environment at a high temperature. The simulations were validated with phosphorothioate interference mapping experiments that help to identify crucial inner-sphere Mg2+ sites prescribing an appropriate initial distribution of inner- and outer-sphere magnesium ions to maintain a physiological ion concentration of monovalent and divalent salts. A concerted role of two chelated magnesium ions is newly discovered since the presence of both supports the formation of the pseudoknot. This constitutes a logical AND gate. The absence of any of these magnesium ions instigates the dissociation of long-range pseudoknot interaction exposing the inner core of the RNA. A base triple is the epicenter of the magnesium chelation effect. It allosterically controls RNA pseudoknot by bolstering the direct effect of magnesium chelation in protecting the functional fold of RNA to control ON and OFF transcription switching.

Combined preparation based on chelating magnesium by phosphorylated casein. Characteristics of its syntesis

The article is devoted to the development and synthesis of a new drug for use in animal husbandry and veterinary medicine as an immunostimulatory and adaptogenic agent. The basis of the new drug is a combination of magnesium, phosphorus, and casein of cow's milk.&#x0D; Given the important scientific and practical importance for veterinary medicine of innovative drugs that would have pronounced immunostimulatory and adaptogenic properties, the aim of our research is to develop a method of obtaining a new drug with an original composition and further studies of its effectiveness and safety.&#x0D; Modern materials and methods were used to achieve this goal. In particular, mass spectrometry was used on a Waters H-class UPLC liquid high-pressure liquid chromatography spectrometer with a Waters TQ-S micro three-quadrupole detector; atomic emission spectrometer with inductively coupled plasma Analytik-Jena Plasma Quant PQ 9000 Elite; liquid chromatographer with a three-quadrupole mass detector and with analytical column – Waters ACQUITY UPLC BEH C18 1.7μm 2.1x50mm.&#x0D; The result of the work was the development of a method of modification of the casein molecule, which was carried out in several stages: the first stage was the direct phosphorylation of the casein molecule; the second stage of the synthesis was the chelation of magnesium with casein.&#x0D; Based on the results of this work, the following conclusions were formed: 1) the synthesis of a new drug is carried out in two stages: the first – modification of casein by direct phosphorylation and the second stage – chelation of magnesium with casein; 2) it was found that the efficiency of phosphorylation directly correlates with the number of treatment cycles of the reaction mixture and is optimal for three treatment cycles

Comparative transcriptome and proteome profiling of chlorophyll metabolism pathway in four types of Magnolia officinalis

Magnolia officinalis is a traditional Chinese medicine,with many years of cultivating process, M. officinalis leaves show more differentiation types due to the exchange of seeds from different provenances. &quot;Da Ao&quot;(DA), &quot;Xiao Ao&quot;(XA), &quot;Chuan Hou&quot;(CH),and &quot;Liu Ye&quot;(LY)are the main types of M. officinalis in Sichuan province of China,and there were obvious differences in growth rate,chemical composition,leaf shape and leaf colour. This study selected different types of M. officinalis leaves(DA,XA,LY and CH)from Sichuan to determine their chlorophyll content. Transcriptomic level sequencing of different types of M. officinalis leaf tissues was by high-throughput sequencing analysis and proteomics used an integrated approach involving TMT labelling and LC-MS/MS to quantify the dynamic changes of the whole proteome of M. officinalis. The results showed that CH had the lowest chlorophyll content while DA had the highest chlorophyll content. Furthermore,transcriptome and proteomics results showed that chlorophyll synthesis pathway in DA glutamine-tRNA reductase,urinary porphyrins decarboxylase(UROD),oxygen-dependent protoporphyrin(ODCO),the original-Ⅲ oxidase protoporphyrin oxidase(PPO),magnesium chelating enzyme subunit ChlD,protoporphyrin magnesium Ⅸ monomethyl ester [oxidative] cyclase(MPPMC)were significantly higher than CH,XA and LY,consistent in the results of determination of chlorophyll content(chlorophyll content was highest of 37.56 mg·g~(-1) FW). Some rate-limiting enzymes related to the chlorophyll synthesis,such as ODCO,PPO and MPPMC were tested by Parallel Reaction Monitoring(PRM),and the results showed that the rate-limiting enzyme content in DA was higher than that in other three types. Therefore,based on the differences in leaf color of four types of M. officinalis,the research conducted a preliminary study on the chlorophyll metabolism pathway in leaves of different types of M. officinalis,and explored relevant genes and proteins causing leaf color differences from the molecular level,so as to lay a foundation for studying the differences in growth and development of different types of M. officinalis.

Molecular mechanisms of atlastin-mediated ER membrane fusion revealed by a FRET-based single-vesicle fusion assay

Homotypic fusion of endoplasmic reticulum membranes is driven by atlastin GTPases; however, the underlying mechanism remains largely unknown. Here, using a FRET-based single-vesicle fusion assay with liposomes bearing the yeast atlastin Sey1p, we investigated the molecular mechanisms of atlastin-mediated membrane tethering and fusion. Although Sey1p-bearing proteoliposomes frequently underwent membrane tethering in a GTP hydrolysis-dependent manner as reported in studies using bulk assays, only a small fraction of the tethered liposomes proceeded to fusion. Strikingly, the rest of the tethered liposomes failed to fuse or dissociate. This stable tethering, however, did not require continued GTP hydrolysis because GTP omission and magnesium chelation did not disrupt tethering. Interestingly, an increased Sey1p density on the membrane markedly accelerated tethering but barely affected the fusion rate of the tethered liposomes, indicating that Sey1p requires additional factors to support efficient fusion in vivo. Finally, the assay also revealed that Sey1p-mediated liposome fusion occurs through hemifusion, suggesting the mechanistic conservation between biological membrane fusion events despite the existence of diverse fusogens.

Development of functionalized carrageenan, chitosan and alginate as polymeric chelating ligands for water softening

Chitosan, carrageenan and alginate are among the most abundant biopolymers in nature. They were prepared in uniform beads shape with a diameter of 2 mm ± 10%, using the encapsulator for removal of calcium, magnesium and iron cations from hard water. Solutions of 100–500 mg/L were prepared from each cation, and the detection of cations was carried out using atomic absorption spectrometer. Carrageenan and chitosan were able to chelate the three cations without further modification. However, alginate beads succeeded to chelate iron and magnesium and failed to chelate any calcium ions; in contrast, it increased the initial calcium concentration! That could be due to the pre-cross-linking of alginate beads using calcium chloride solution, which may be leaked back to the solution. However, grafting the alginate beads with polyethyleneimine and bromoacetic acid rectified this problem and the new functional group, –COOH, has been proved using the FT-IR. Optimization of the results in terms of beads weight (0.25–3.0 g) and cations concentrations (100–500 mg/L) has shown that most biopolymeric beads can chelate 85–100% of the cations in concentrations up to 500 mg/L. According to our finding, we came up with the recommendation to use chitosan for chelation of calcium and iron as it showed 100% chelation efficiency of both cations, whereas carrageenan is highly recommended for chelation of iron and magnesium, as it showed 100 and 98% chelation efficiency, respectively. Further work can be done on the reusability of the beads and scale up for the industrial use.

Metal Chelation as a Powerful Strategy to Probe Cellular Circuitry Governing Fungal Drug Resistance and Morphogenesis.

Fungal pathogens have evolved diverse strategies to sense host-relevant cues and coordinate cellular responses, which enable virulence and drug resistance. Defining circuitry controlling these traits opens new opportunities for chemical diversity in therapeutics, as the cognate inhibitors are rarely explored by conventional screening approaches. This has great potential to address the pressing need for new therapeutic strategies for invasive fungal infections, which have a staggering impact on human health. To explore this approach, we focused on a leading human fungal pathogen, Candida albicans, and screened 1,280 pharmacologically active compounds to identify those that potentiate the activity of echinocandins, which are front-line therapeutics that target fungal cell wall synthesis. We identified 19 compounds that enhance activity of the echinocandin caspofungin against an echinocandin-resistant clinical isolate, with the broad-spectrum chelator DTPA demonstrating the greatest synergistic activity. We found that DTPA increases susceptibility to echinocandins via chelation of magnesium. Whole genome sequencing of mutants resistant to the combination of DTPA and caspofungin identified mutations in the histidine kinase gene NIK1 that confer resistance to the combination. Functional analyses demonstrated that DTPA activates the mitogen-activated protein kinase Hog1, and that NIK1 mutations block Hog1 activation in response to both caspofungin and DTPA. The combination has therapeutic relevance as DTPA enhanced the efficacy of caspofungin in a mouse model of echinocandin-resistant candidiasis. We found that DTPA not only reduces drug resistance but also modulates morphogenesis, a key virulence trait that is normally regulated by environmental cues. DTPA induced filamentation via depletion of zinc, in a manner that is contingent upon Ras1-PKA signaling, as well as the transcription factors Brg1 and Rob1. Thus, we establish a new mechanism by which metal chelation modulates morphogenetic circuitry and echinocandin resistance, and illuminate a novel facet to metal homeostasis at the host-pathogen interface, with broad therapeutic potential.

NMR investigation of magnesium chelation and cation-induced signal shift effect of testosterone

We have previously reported that testosterone (Tes) is able to interact with magnesium chloride dissolved in methanol. In this study, we have applied 1H and 13C NMR spectroscopies to a series of Tes solutions containing Mg2+ at various concentrations. High-resolution 13C NMR spectra of Tes/Mg2+ revealed well-resolved 13C signals, and the intensities of those arising from C3, C5, C16, and C17 decreased linearly with increasing Mg2+ concentration. The magnitude of the chelation affinity could be deduced from the slopes of the 13C intensity variations; typically, the greater the slope the higher the chelation affinity. The results revealed Tes/Mg2+ chelation to be mediated by the oxygen atom attached to C3 in ring A, and the hydroxyl group attached to C17 in ring D. With regard to the chelation specificity, we showed that Tes chelates Mg2+, but not Ca2+ or Zn2+. We also explored the cation-induced signal shift effects of Tes in the presence of Mg2+, Ca2+, or Zn2+. We demonstrate that high-resolution 13C NMR spectroscopy provides a better probe than 1H NMR for the detection of cation chelation and cation-induced signal shift effects for steroid compounds such as Tes.

Synthesis and characterization of color-tunable mixed ligand based magnesium complexes for display device applications

In this study, we reported the synthesis and the characterization of mixed-ligand based magnesium chelates with 2-(2-hydroxyphenyl)-1H-benzimidazole (HBI) and 8-hydroxyquinoline (Q) or 5-chloro-8-hydroxyquinoline (ClQ) or 5,7-dichloro-8-hydroxyquinoline (Cl2Q) or 2-methyl-8-hydroxyquinoline (MeQ) or 5,7-dimethyl-8-hydroxyquinoline (Me2Q). The photophysical properties of these metal complexes has been investigated by UV–visible absorption and photoluminescence spectroscopy. The electrochemical behaviour of metal complexes was also reported. The metal complexes had good thermal stability (>300 °C). All prepared metal complexes exhibited bright colored light on excitation with a UV light source. The emitted light had color coordinates values at x = 0.17, y = 0.36 for [Mg(HBI)(Q)]; x = 0.21, y = 0.47 for [Mg(HBI)(ClQ)]; x = 0.16, y = 0.26 for [Mg(HBI)(Cl2Q)]; x = 0.16, y = 0.25 for [Mg(HBI)(MeQ)]; and x = 0.30, y = 0.58 for [Mg(HBI)(Me2Q)] material. Color tuning by modifying the substituents in 8-hydroxyquinoline ligand was examined in synthesized complexes. In addition, a temperature-dependence photoluminescence spectrum was used to study the emission profile of magnesium complexes. Density functional theoretical calculations had been performed to demonstrate the three-dimensional geometries and the frontier molecular orbitals energy level of metal complexes. Complexes emitting color tuned luminescence could be efficiently used for the fabrication of next generation display devices.

Experimental screening of some chelating agents for calcium and magnesium removal from saline solutions

Removal of hardness-causing ions from seawater and desalination brines improves the performance of water treatment units and provides economic and environmental benefits. Chelation of calcium (Ca2+) and magnesium (Mg2+) ions in saline solutions has been experimentally investigated as a stand-alone separation process. In the current study, ethylene glycol bis(2-aminoethyl ether)-N,N,N′,N′-tetraacetic acid (EGTA), diethylenetriaminepentaacetic acid (DTPA), N-(2-Hydroxyethyl) ethylene diamine-N,N′,N′-triacetic acid (HEDTA), ethylene diaminetetraacetic acid (EDTA), polyacrylic acid (PAA), boric acid (BA), and sodium tripolyphosphate (STP) were selected as chelating agents. It was found that DTPA exhibited the maximum Ca2+-loading capacity of 128 mg/g and minimum Mg2+-loading capacity at pH 3 for the Mediterranean Seawater. The corresponding values for EGTA in Red Seawater were 117 and 2 mg/g and were obtained at pH 3 and 6.6, respectively, with an EGTA optimum dose of 1 g/L. Maximum Ca2+ and Mg2+ loading capacities (153 and 72 mg/g, respectively) were attained using EDTA with reverse osmosis brine. On the other hand, EDTA exhibited the highest calcium and magnesium loadings (158 and 76 mg/g) with Red Seawater at pH 7.5. Among the investigated chelating agents, EGTA and EDTA were found to be the most suitable for softening of Red Seawater, whereas EGTA proved to be the most selective for calcium ions. Both calcium and magnesium adsorption onto EGTA have been best described by Langmuir isotherm indicating monolayer coverage of ions on the outer surface of the chelating agent.

Synthesis of methyl (132R/S)-alkyl-pyropheophorbide a and a non-epimerized chlorophyll a mimic

The (132R/S)-methoxycarbonyl group of methyl pheophorbides a/a′ (chlorophyll a/a′ derivatives) was converted to methyl, ethyl, propyl, and isopropyl groups through the C132-alkylation under basic conditions followed by pyrolysis in 2,4,6-collidine with lithium iodide. All the resulting products, methyl 132-alkyl-pyropheophorbides a, predominantly gave the (132R)-stereoisomers with about one tenth of the (132S)-epimers. Their stereochemistry was determined by 1D/2D NMR and their optical properties were characterized by visible absorption and circular dichroism spectroscopy. Methyl (132R)-propyl-pyropheophorbide a was converted to (132R)-propyl-pyrochlorophyll a by ester exchanging and magnesium chelating reactions. The synthetic chlorophyll a analogue showed non-epimerization at the 132-position in pyridine-d5 at 40°C, while naturally occurring chlorophyll a was easily epimerized under the same conditions to give its epimeric mixture.

Purification and characterization of a phenoloxidase in the hemocytes of Ephestia kuehniella Zeller (Lepidoptera: Pyralidae): effects of insect growth regulators and endogenous inhibitors

A phenoloxidase was extracted and purified from hemocytes of Ephestia kuehniella by using ammonium sulfate, Sepharyl G-100 and DEAE-Cellulose fast flow chromatographies. At the final stage of purification, a protein was purified by molecular mass of 78.5 kDa, specific activity of 1.17 U/mg protein, recovery of 20.48% and purification fold of 16.71. The purified PO showed the highest activity at pH 4–5 and temperatures of 35–40 °C. Na+, K+, Mn+, Zn2+ and Mg2+ decreased activity of the purified PO but Ca2+ and Cu2+ increased the enzymatic activity. EDTA (General chelating agent), DTC (Copper chelating agent) and EGTA (Calcium chelating agent) significantly decreased PO activity but TTHA (Magnesium chelating agent) showed no statistically significant effects. Kinetic parameters of the purified enzyme showed the highest Vmax when L-DOPA was used as substrate but no significant differences were observed in case of Km for used L-DOPA, pyrocatechol and hydroquinone. In vitro inhibition of the purified PO by using two insect growth regulators, Hexaflumuron and Pyriproxyfen, revealed IC50 of 96.41 and 38.59 µg/ml for these compounds, respectively. Kinetic studies using different concentrations of L-DOPA and IC50 concentrations of the two IGRs revealed the increase of Km value versus control and competitive inhibition. Finally, column chromatography of hemolymph revealed peak III showing endogenous inhibitors of phenoloxidase by molecular weight of 27.3 that showed competitive inhibition on the PO.

The Influence of Nucleotide Sequence and Temperature on the Activity of Thermostable DNA Polymerases

Extension rates of a thermostable, deletion-mutant polymerase were measured from 50°C to 90°C using a fluorescence activity assay adapted for real-time PCR instruments. Substrates with a common hairpin (6-base loop and a 14-bp stem) were synthesized with different 10-base homopolymer tails. Rates for A, C, G, T, and 7-deaza-G incorporation at 75°C were 81, 150, 214, 46, and 120 seconds(-1). Rates for U were half as fast as T and did not increase with increasing concentration. Hairpin substrates with 25-base tails from 0% to 100% GC content had maximal extension rates near 60% GC and were predicted from the template sequence and mononucleotide incorporation rates to within 30% for most sequences. Addition of dimethyl sulfoxide at 7.5% increased rates to within 1% to 17% of prediction for templates with 40% to 90% GC. When secondary structure was designed into the template region, extension rates decreased. Oligonucleotide probes reduced extension rates by 65% (5'-3' exo-) and 70% (5'-3' exo+). When using a separate primer and a linear template to form a polymerase substrate, rates were dependent on both the primer melting temperature (Tm) and the annealing/extension temperature. Maximum rates were observed from Tm to Tm - 5°C with little extension by Tm + 5°C. Defining the influence of sequence and temperature on polymerase extension will enable more rapid and efficient PCR.