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Metallomics : Integrated Biometal... Jul 2022Aspergillus fumigatus, one of the most widespread opportunistic human fungal pathogens, adapts to zinc limitation by secreting a 310 amino acid Aspf2 zincophore, able to...
Aspergillus fumigatus, one of the most widespread opportunistic human fungal pathogens, adapts to zinc limitation by secreting a 310 amino acid Aspf2 zincophore, able to specifically bind Zn(II) and deliver it to a transmembrane zinc transporter, ZrfC. In this work, we focus on the thermodynamics of Zn(II) complexes with unstructured regions of Aspf2; basing on a variety of spectrometric and potentiometric data, we show that the C-terminal part has the highest Zn(II)-binding affinity among the potential binding sites, and Ni(II) does not compete with Zn(II) binding to this region. The 14 amino acid Aspf2 C-terminus coordinates Zn(II) via two Cys thiolates and two His imidazoles and it could be considered as a promising A. fumigatus targeting molecule.
Topics: Amino Acids; Aspergillus fumigatus; Binding Sites; Humans; Protein Domains; Zinc
PubMed: 35700143
DOI: 10.1093/mtomcs/mfac042 -
Materials (Basel, Switzerland) Nov 2021Sodium-vanadium oxide NaVO is synthesized via solid-state method and optimum synthesis conditions are chosen based on the data of DSC and TG analysis. The material...
Sodium-vanadium oxide NaVO is synthesized via solid-state method and optimum synthesis conditions are chosen based on the data of DSC and TG analysis. The material synthesized is characterized by X-ray phase analysis, Raman spectroscopy and scanning electron microscopy. The ratio V/V in the sample obtained is determined by X-ray photoelectron spectroscopy. Conductivity of the material synthesized was measured by impedance spectroscopy, pulse potentiometry and DC method over the range RT-570 °C. It is shown that NaVO has rather high conductivity essentially electron in type (6.3 × 10 at room temperature). AC and DC conductivity measurements are performed and cycling of symmetricNaVO|NaZrNbSiO|NaVO cell in galvanostatic conditions. Thermal stability is studied across 25-570 °C temperature range. The results obtained are compared with the properties of NaVO produced via aqueous solution.
PubMed: 34832378
DOI: 10.3390/ma14226976 -
Sensors (Basel, Switzerland) Nov 2022Herein, we developed a new pencil graphite ion-selective electrode strategy for the broadly used erectile dysfunction medication, sildenafil citrate (SC, vitamin V), for...
Two Versatile Pencil Graphite-Polymer Sensor Electrodes Coupled with Potentiometry and Potentiometric Titration Methods: Profiling Determinations of Vitamin V in Tablets and Urine Samples.
Herein, we developed a new pencil graphite ion-selective electrode strategy for the broadly used erectile dysfunction medication, sildenafil citrate (SC, vitamin V), for its automated potentiometry and potentiometric titration profiling in marketed tablets and human urine samples. The method was based on ion-pair complexation between SC and sodium tetraphenylborate (Na-TPB) or phosphotungstic acid (PTA), embedded into a pencil-fabricated graphite sensor electrode coated with poly(vinyl chloride, PVC) matrix, which is pre-plasticized with two different pre-studied plasticizers. The modern fabricated electrodes have a proven fast near-Nernstian response for SC over the concentration range of 1.0 × 10 to 1.0 × 10 and 1.0 × 10 to 1.0 × 10 M, with LODs of 6.5 × 10 and 5.5 × 10 over a pH 3-6 for (SC-TPB)- and (SC-PTA)-based membrane sensors, of O-nitrophenyl octyl ether (O-NPOE) and dioctyl phthalate (DOP), respectively. The selectivity coefficients for different interferents, including many inorganic cations, sugars, and/or nitrogenous compounds, were tested and confirmed. Applications of the proposed method were conducted on the determination of SC in its tablets and urine samples under the proper conditions. The percent recovery values were compared with those obtained by an official method and showed an RSD ≤ 0.3% ( = 5).
Topics: Humans; Graphite; Polymers; Vitamins; Hydrogen-Ion Concentration; Ion-Selective Electrodes; Tablets; Cations
PubMed: 36501827
DOI: 10.3390/s22239128 -
Analytical Science Advances Jun 2021In this paper, we demonstrate the suitability, sensitivity, and precision of low-cost and easy-to-use ion-selective electrodes (ISEs) for concurrent detection of NH and...
In this paper, we demonstrate the suitability, sensitivity, and precision of low-cost and easy-to-use ion-selective electrodes (ISEs) for concurrent detection of NH and NO in soil and water by technical and non-technical end-users to enable efficient soil and water management exposed to chronic reactive nitrogen loading. We developed a simplified methodology for sample preparation followed by the demonstration of an analytical methodology resulting in improvements of sensitivity and precision of ISEs. Herein, we compared and contrasted ISEs with traditional laboratory-based technique such as Flow Injection Analysis (FIA) and portable colorimetric assay followed by comparisons of linear regression and Bayesian nonlinear calibration approaches applied on both direct potentiometry and standard addition modes of analysis in terms of in-field applications and improvement of sensitivity and precision. The ISEs were validated for sensing on a range of ambient soil and water samples representing a range of NH and NO concentrations from pristine to excessive saturation conditions. Herein developed methodology showed excellent agreement with lab-based and portable analytical techniques while demonstrating improvements in precision and sensitivity analysis illustrated by a decrease in confidence intervals by 50-60%. We also demonstrated the utilization of the entire ISE response curve thus removing the biases originating from linear approximation which is often currently employed. Therefore, we show that ISEs are robust yet low cost and an easy to use technology that can enable high-frequency measurement of mineral N and help to improve our understanding of N transformation processes as influenced by soil management, fertilization, land use, and climate change.
PubMed: 38716159
DOI: 10.1002/ansa.202000124 -
Journal of the American Chemical Society Jun 2024Arsenic is highly toxic and a significant threat to human health, but certain bacteria have developed defense mechanisms initiated by As binding to As-sensing proteins...
Arsenic is highly toxic and a significant threat to human health, but certain bacteria have developed defense mechanisms initiated by As binding to As-sensing proteins of the ArsR family. The transcriptional regulator AfArsR responds to As and Sb by coordinating the metalloids with three cysteines, located in a short sequence of the same monomer chain. Here, we characterize the binding of As and Hg to a model peptide encompassing this fragment of the protein via solution equilibrium and spectroscopic/spectrometric techniques (pH potentiometry, UV, CD, NMR, PAC, EXAFS, and ESI-MS) combined with DFT calculations and MD simulations. Coordination of As changes the peptide structure from a random-coil to a well-defined structure of the complex. A trigonal pyramidal AsS binding site is formed with almost exactly the same structure as observed in the crystal structure of the native protein, implying that the peptide possesses all of the features required to mimic the As recognition and response selectivity of AfArsR. Contrary to this, binding of Hg to the peptide does not lead to a well-defined structure of the peptide, and the atoms near the metal binding site are displaced and reoriented in the Hg model. Our model study suggests that structural organization of the metal site by the inducer ion is a key element in the mechanism of the metalloid-selective recognition of this protein.
Topics: Arsenic; Binding Sites; Bacterial Proteins; Metalloids; Density Functional Theory; Molecular Dynamics Simulation; Protein Binding
PubMed: 38820242
DOI: 10.1021/jacs.3c11665 -
Journal of Functional Biomaterials Dec 2022There has been profound growth in the use of 3D printed materials in dentistry in general, including orthodontics. The opportunity to impart antimicrobial properties to...
There has been profound growth in the use of 3D printed materials in dentistry in general, including orthodontics. The opportunity to impart antimicrobial properties to 3D printed parts from existing resins requires the capability of forming a stable colloid incorporating antimicrobial fillers. The objective of this research was to characterize a colloid consisting of a 3D printable resin mixed with Ag-ion releasing zeolites and fumed silica to create 3D printed parts with antiviral properties. The final composite was tested for antiviral properties against SARS-CoV-2 and HIV-1. Antiviral activity was measured in terms of the half-life of SARS-CoV-2 and HIV-1 on the composite surface. The inclusion of the zeolite did not interfere with the kinetics measured on the surface of the ATR crystal. While the depth of cure, measured following ISO4049 guidelines, was reduced from 3.8 mm to 1.4 mm in 5 s, this greatly exceeded the resolution required for 3D printing. The colloid was stable for at least 6 months and the rheological behavior was dependent upon the fumed silica loading. The inclusion of zeolites and fumed silica significantly increased the flexural strength of the composite as measured by a 3 point bend test. The composite released approximately 2500 μg/L of silver ion per gram of composite as determined by potentiometry. There was a significant reduction of the average half-life of SARS-CoV-2 (1.9 fold) and HIV-1 (2.7 fold) on the surface of the composite. The inclusion of Ag-ion releasing zeolites into 3D-printable resin can result in stable colloids that generate composites with improved mechanical properties and antiviral properties.
PubMed: 36662054
DOI: 10.3390/jfb14010007 -
Biochimica Et Biophysica Acta.... Mar 2022The Mo-dependent enzyme YiiM enzyme from Escherichia coli is a member of the sulfite oxidase family and shares many similarities with the well-studied human...
The Mo-dependent enzyme YiiM enzyme from Escherichia coli is a member of the sulfite oxidase family and shares many similarities with the well-studied human mitochondrial amidoxime reducing component (mARC). We have investigated YiiM catalysis using electrochemical and spectroscopic methods. EPR monitored redox potentiometry found the active site redox potentials to be Mo -0.02 V and Mo -0.12 V vs NHE at pH 7.2. In the presence of methyl viologen as an electrochemically reduced electron donor, YiiM catalysis was studied with a range of potential substrates. YiiM preferentially reduces N-hydroxylated compounds such as hydroxylamines, amidoximes, N-hydroxypurines and N-hydroxyureas but shows little or no activity against amine-oxides or sulfoxides. The pH optimum for catalysis was 7.1 and a bell-shaped pH profile was found with pK values of 6.2 and 8.1 either side of this optimum that are associated with protonation/deprotonations that modulate activity. Simulation of the experimental voltammetry elucidated kinetic parameters associated with YiiM catalysis with the substrates 6-hydroxyaminopurine and benzamidoxime.
Topics: Catalysis; Catalytic Domain; Escherichia coli; Humans; Kinetics; Molybdenum; Oxidation-Reduction
PubMed: 34921810
DOI: 10.1016/j.bbabio.2021.148523 -
Biosensors Jun 2023Triturated seeds have components that adsorb recalcitrant indigo carmine dye. Coagulating proteins known as lectins (carbohydrate-binding proteins) have already been...
Triturated seeds have components that adsorb recalcitrant indigo carmine dye. Coagulating proteins known as lectins (carbohydrate-binding proteins) have already been purified from the powder of these seeds, in milligram amounts. The coagulant lectin from seeds (cMoL) was characterized by potentiometry and scanning electron microscopy (SEM) using MOFs, or metal-organic frameworks, of [Cu(BTC)(HO)] to immobilize cMoL and construct biosensors. The potentiometric biosensor revealed an increase in the electrochemical potential resulting from the Pt/MOF/cMoL interaction with different concentrations of galactose in the electrolytic medium. The developed aluminum batteries constructed with recycled cans degraded an indigo carmine dye solution; the oxide reduction reactions of the batteries generated Al(OH), promoting dye electrocoagulation. Biosensors were used to investigate cMoL interactions with a specific galactose concentration and monitored residual dye. SEM revealed the components of the electrode assembly steps. Cyclic voltammetry showed differentiated redox peaks related to dye residue quantification by cMoL. Electrochemical systems were used to evaluate cMoL interactions with galactose ligands and efficiently degraded dye. Biosensors could be used for lectin characterization and monitoring dye residues in environmental effluents of the textile industry.
Topics: Lectins; Moringa oleifera; Indigo Carmine; Galactose; Seeds; Carmine
PubMed: 37367020
DOI: 10.3390/bios13060655 -
International Journal of Environmental... Oct 2022The use of fluoride is effective in preventing dental caries. However, an excessive intake of fluoride leads to dental fluorosis, making it necessary to regularly...
The use of fluoride is effective in preventing dental caries. However, an excessive intake of fluoride leads to dental fluorosis, making it necessary to regularly monitor the fluoride intake especially for infants. There is hitherto a lack of information on fluoride content in infant foods from an Australian perspective. Therefore, this study aims to estimate the amount of fluoride content from a range of commercially available ready-to-eat (RTE) infant foods and drinks available in Australia. Based on an external calibration method, potentiometry involving a fluoride ion selective electrode and a silver|silver chloride reference electrode was conducted to analyse the fluoride content of a total of 326 solid food samples and 49 liquid food samples in this work. Our results showed an overall median (range) fluoride content of 0.16 (0.001-2.8) µg F/g of solid food samples, and 0.020 (0.002-1.2) µg F/mL of liquid food samples. In addition, ~77.5% of the liquid samples revealed a fluoride content < 0.05% µg F/mL. The highest variation of fluoride concentration (0.014-0.92 µg F/g) was found in formulas for ≥6 month-old infants. We have attributed the wide fluoride content variations in ready-to-eat infant foods and drinks to the processing steps, different ingredients and their origins, including water. In general, we found the fluoride content in most of the collected samples from Australian markets to be high and may therefore carry a risk of dental fluorosis. These results highlight the need for parents to receive appropriate information on the fluoride content of ready-to-eat infant food and drinks.
Topics: Infant; Humans; Fluorides; Fluorosis, Dental; Dental Caries; Australia; Infant Food; Infant Formula
PubMed: 36360963
DOI: 10.3390/ijerph192114087 -
Inorganic Chemistry Aug 2020Owing to the increasing importance of manganese(II) complexes in the field of magnetic resonance imaging (MRI), large efforts have been devoted to find an appropriate...
Owing to the increasing importance of manganese(II) complexes in the field of magnetic resonance imaging (MRI), large efforts have been devoted to find an appropriate ligand for Mn(II) ion encapsulation by providing balance between the seemingly contradictory requirements (i.e., thermodynamic stability and kinetic inertness vs low ligand denticity enabling water molecule(s) to be coordinated in its metal center). Among these ligands, a large number of pyridine or pyridol based open-chain and macrocyclic chelators have been investigated so far. As a next step in the development of these chelators, 15-pyNOPh and its transition metal complexes were synthesized and characterized using established methods. The 15-pyNOPh ligand incorporates both pyridine and -phenylene units to decrease ligand flexibility. The thermodynamic properties, protonation and stability constants, were determined using pH-potentiometry; the solid-state structures of two protonation states of the free ligand and its manganese complex were obtained by single crystal X-ray diffractometry. The results show a seven-coordinate metal center with two water molecules in the first coordination sphere. The longitudinal relaxivity of [Mn(15-pyNOPh)] was found to be 5.16 mM s at 0.49 T (298 K). Furthermore, the value of 11.72 mM s (0.49 T), which is doubled at 1.41 T field, suggests that design of this Mn(II) complex does achieve some characteristics required for contrast imaging. In addition, O NMR measurements were performed in order to access the microscopic parameters governing this key feature (e.g., water exchange rate). Finally, manganese complexes of ligands with analogous polyaza macrocyclic scaffold have been investigated as low molecular weight Mn(CAT) mimics. Here, we report the HO disproportionation study of [Mn(15-pyNOPh)] to demonstrate the versatility of this ligand scaffold as well.
PubMed: 32709206
DOI: 10.1021/acs.inorgchem.0c01053