Oxygenation through oral Ox66 in a two-hit rodent model of respiratory distress

Acute respiratory distress syndrome (ARDS) is a complication of pulmonary disease that produces life-threatening hypoxaemia. Despite ventilation and hyperoxic therapies, undetected hypoxia can manifest in capillary beds leading to multi-organ failure. Ox66™ is an ingestible, solid-state form of oxygen designed to supplement oxygen deficits. Twenty-four anaesthetized rats underwent a two-hit model of respiratory distress (ARDS), where a single dose (5 mg/kg) of lipopolysaccharide (LPS) was given intratracheally, and then the respiratory tidal volume was reduced by 40%. After 60 min, animals were randomized to receive Ox66™, or normal saline (NS; vehicle control) via gavage or supplemental inspired oxygen (40% FiO2). A second gavage was administered at 120 min. Cardiovascular function and blood oximetry/chemistry were measured alongside the peripheral spinotrapezius muscle's interstitial oxygenation (PISFO2). ARDS reduced mean arterial pressure (MAP) and PISFO2 compared to baseline (BL) for all treatment groups. Treatment with Ox66 or NS did not improve MAP, but 40% FiO2 caused a rapid return to BL. PISFO2 improved after treatment with Ox66™ and 40% FiO2 and remained elevated for both groups against NS until study conclusion. Both oxygen treatments also suppressed the inflammatory response to LPS, suggesting that Ox66™ can deliver therapeutically-impactful levels of oxygen in situations of pulmonary dysfunction.

Metabolomic Profile and Functional State of Oat Plants (Avena sativa L.) Sown under Low-Temperature Conditions in the Cryolithozone

Oats are one of the most useful and widespread cereal crops in the world. In permafrost conditions (Central Yakutia), based on metabolic changes in late summer-sown oat plants (Avena sativa L.), the key processes involved in the cold acclimation of a valuable cereal species were identified. During the onset of low ambient temperatures, metabolites from leaf samples were profiled using gas chromatography with mass spectrometry (GC-MS) and were analyzed using principal component analysis (PCA). A total of 41 metabolites were identified in oat leaves. It was found that acclimation to suboptimal temperatures during the fall period leads to biochemical (accumulation of mono- and disaccharides and decrease in fatty acids and polyols) as well as physiological and biophysical changes (decrease in leaf PRI reflectance indices and chlorophyll a fluorescence). Therefore, the study contributes to a more holistic understanding of oat metabolism under low-temperature cryolithozone stress. It is believed that the analysis of changes in leaf reflection properties and JIP-test parameters of chlorophyll a fluorescence using leaf metabolomic profiling can be used in the selection of valuable varieties of cereal crops to obtain plant fodders with high nutrient contents under conditions of a sharply continental climate.

Green spectrophotometric and spectrofluorimetric determination of biperiden hydrochloride using erythrosine B sensing probe

Erythrosine B (EB) is a food colorant antiviral xanthene dye that has many applications as a color additive in pharmaceuticals and cosmetics. Its use as a sensor for spectrofluorimetric and spectrophotometric analysis of amine-based pharmaceuticals renders many advantages because of its availability, low cost, rapid labeling, and high sensitivity. Herein, two fast and sensitive spectrofluorimetric and spectrophotometric methods were established for the estimation of the anti-Parkinson drug, biperiden (BIP) hydrochloride (HCl), in its raw material and tablet forms. The proposed methods depended on the interaction between the phenolic group of EB and the tertiary amino group of the studied analyte to form an ion-pair complex at pH 4 using the Britton Robinson buffer. The spectrofluorimetric method is based on the measurement of the quenching power of BIP HCl on the fluorescence intensity of EB at λex/em = 527.0/550.9 nm. This method was rectilinear over the concentration range of 0.1-1.0 μg/mL with a limit of detection (LOD) = 0.017 μg/mL and a limit of quantification (LOQ) = 0.05 μg/mL. Meanwhile, the colorimetric method involved monitoring the absorbance of the formed ion-pair complex at 555 nm, showing a linearity range of 0.4-5.0 μg/mL with LOD = 0.106 μg/mL and LOQ = 0.322 μg/mL. The proposed methods were assessed for the greenness, indicating the greenness of the developed methods.

Controllable Technology for Thermal Expansion Coefficient of Commercial Materials for Solid Oxide Electrolytic Cells

Solid oxide electrolysis cell (SOEC) industrialization has been developing for many years. Commercial materials such as 8 mol% Y2O3-stabilized zirconia (YSZ), Gd0.1Ce0.9O1.95 (GDC), La0.6Sr0.4Co0.2Fe0.8O3-δ (LSCF), La0.6Sr0.4CoO3-δ (LSC), etc., have been used for many years, but the problem of mismatched thermal expansion coefficients of various materials between cells has not been fundamentally solved, which affects the lifetime of SOECs and restricts their industry development. Currently, various solutions have been reported, such as element doping, manufacturing defects, and introducing negative thermal expansion coefficient materials. To promote the development of the SOEC industry, a direct treatment method for commercial materials-quenching and doping-is reported to achieve the controllable preparation of the thermal expansion coefficient of commercial materials. The quenching process only involves the micro-treatment of raw materials and does not have any negative impact on preparation processes such as powder slurry and sintering. It is a simple, low-cost, and universal research strategy to achieve the controllable preparation of the thermal expansion coefficient of the commercial material La0.6Sr0.4Co0.2Fe0.8O3-δ (LSCF) through a quenching process by doping elements and increasing oxygen vacancies in the material. Commercial LSCF materials are heated to 800 °C in a muffle furnace, quickly removed, and cooled and quenched in 3.4 mol/L of prepared Y(NO3)3. The thermal expansion coefficient of the treated material can be reduced to 13.6 × 10-6 K-1, and the blank sample is 14.1 × 10-6 K-1. In the future, it may be possible to use the quenching process to select appropriate doping elements in order to achieve similar thermal expansion coefficients in SOECs.

Optical properties of blue-light-emitting Y2 O3 :Ce nanophosphor for solid-state lighting application

The structural, surface morphological, optical absorption and emission features of Y2 O3 :Ce (0%-5%) were studied. The samples had a body-centred cubic crystal structure. The undoped sample had a crystallite size of 29.03 nm, and it varied after doping with Ce. The grain size of the samples varied from 23.00 to 50.78 nm. All the samples exhibited a strong absorption band at 206 nm due to F-centre absorption and absorption involving the delocalised bands. In addition, the doped samples exhibited a secondary band at ~250 nm due to 4f → 5d transitions of Ce3+ ions. The optical bandgap of the undoped sample was found to be ~5.37 eV, and it decreased to 5.20 eV with an increase in Ce concentration to 5%. The undoped sample under 350-nm excitation exhibited a broad photoluminescence (PL) emission band with the maxima at 406 nm and a secondary band at 463 nm. In contrast, multiple PL peaks were centred at ~397, 436, 466, 488 and 563 nm in all the doped samples. The average lifetime of the emission band at 406 nm was 1.05 ns and that of the emission band at ~466 nm was 1.63 ns. The material has potential for solid-state lighting applications.

Synthesis of 4-sulfamoyl phenyl diazocarboxylic acid derivatives as novel non-classical inhibitors of human carbonic anhydrase II activity: an in vitro study

The first class of carbonic anhydrase inhibitors (CAIs) discovered was sulfonamides, but their clinical use is limited due to side effects caused by their inhibition of multiple CA isoforms. To overcome this, researchers have focused on developing isoform-selective CAIs. This study involved the synthesis and characterization of novel carboxylic acid/sulfonamide derivatives. We investigated the interaction between these compounds and the human carbonic anhydrase II (hCA II) isoform using spectroscopic and computational methods. The synthesized compounds were evaluated based on their IC50, Kd and Ki values, and it was found that the inhibitory potency and binding affinity of the compounds increased with the number of carboxylic acids zinc binding groups. Specifically, the compound C4, with three carboxylic acid groups, showed the strongest inhibitory potency. Fluorescence measurements revealed that all compounds quenched the intrinsic fluorescence of hCA II through a dynamic quenching process, and each compound had one binding site in the hCA II structure. Thermodynamic analysis indicated hydrogen bonds and van der Waals interactions played key roles in the binding of these compounds to hCA II. Docking studies showed that the carboxylic acid groups directly attached to the zinc ion in the active site, displacing water/hydroxide ions and causing steric hindrance. Overall, the strengthening of inhibitory activity and the binding power of these carboxylic acid derivatives for the hCA II makes these compounds interesting for designing novel hCA II inhibitors.Communicated by Ramaswamy H. Sarma.

Eco-friendly approach for the determination of moxifloxacin in pharmaceutical formulations and biological fluids based on fluorescence quenching of l-tryptophan

A rapid, novel and cost-effective spectrofluorimetric method developed to determine moxifloxacin (MFX) in pharmaceutical preparations because MFX in a pH 10 medium could reduce the fluorescence intensity of l-tryptophan. The maximum fluorescence excitation and emission wavelengths were found to be 280 and 363 nm respectively. A range of factors affecting fluorescence quenching and the effect of co-existing substances were investigated. Fluorescence quenching values (ΔF = FL-tryptophan  - FMoxi-L-tryptophan ) displayed a strong linear relationship with the MFX concentration ranging from 0.2 to 8.0 μg/ml under optimum conditions. The limit of detection was found to be 6.1 × 10-4  μg/ml. The proposed method was shown to be suitable for MFX determination in pharmaceutical tablets and biological fluids by the linearity, recovery and limit of detection. The spectrofluorimetric approach that has been developed is extremely eco-friendly, as evidenced by the fact that all the experimental components and solvents were safe for the environment.

Effects of Activation Barriers on Quenching to Stabilize Prebiotic Chemical Systems

We have previously shown in model studies that rapid quenches of systems of monomers interacting to form polymer chains can fix nonequilibrium chemistries with some lifelike properties. We suggested that such quenching processes might have occurred at very high rates on early Earth, giving an efficient mechanism for natural sorting through enormous numbers of nonequilibrium chemistries from which the most lifelike ones could be naturally selected. However, the model used for these studies did not take account of activation barriers to polymer scission (peptide bond hydrolysis in the case of proteins). Such barriers are known to exist and are expected to enhance the quenching effect. Here, we introduce a modified model which takes activation barriers into account and we compare the results to data from experiments on quenched systems of amino acids. We find that the model results turn out to be sensitive to the width of the distribution of barrier heights but quite insensitive to its average value. The results of the new model are in significantly better agreement with the experiments than those found using our previous model. The new parametrization of the model only requires one new parameter and the parametrization is more physical than the previous one, providing a chemical interpretation of the parameter p in our previous models. Within the model, a characteristic temperature Tc emerges such that if the temperature of the hot stage is above Tc and the temperature of the cold stage is below it, then the 'freezing out', in a quench, of a disequilibrium ensemble of long polymers is expected. We discuss the possible relevance of this to models of the origin of life in emissions from deep ocean rifts.

Development of a Sensitive and Selective Method for the Determination of some Selected Aldehydes Based on Fluorescence Quenching

Phenanthrene fluorescence quenching in anionic micellar system of sodium dodecyl sulphate (SDS) was explored for the development of a sensitive and selective method for a group of selected aldehydes (2,6-dichlorobenzaldehyde, 4-(dimethylamino)benzaldehyde, 4-aminobenzaldehyde, 4-nitrobenzaldehyde, 2-chlorobenzaldehyde, benzaldehyde and 2-methoxybenzaldehyde). Experiments were performed in 0.02 mol L- 1 SDS. All the studied aldehydes quenched the fluorescence intensity of the probe (phenanthrene). Stern-Volmer equation was useful in explaining the phenanthrene quenching by the studied aldehydes. Stern-Volmer constants ([Formula: see text]) were obtained as a result of using the Stern-Volmer equation that gives the information in respect of sensitivity of the method for the studied aldehydes. Greater the [Formula: see text] higher will be the sensitivity and vice versa. [Formula: see text], detection limit (DL) and quantification limit (QL) were observed in the order 2,6-dichlorobenzaldehyde > 4-dimethylaminobenzaldehyde > 4-aminobenzaldehyde > 4-nitrobenzaldehyde > 2-chlorobenzaldehyde > benzaldehyde > 2-methoxybenzaldehyde. Phenanthrene fluorescence quenching by the studied aldehydes is useful for their determination in environmental samples.

Electric Field-Induced Quenching of MAPbI3 Photoluminescence in PeLED Architecture

Photoluminescence (PL) measurements are a widely used technique for the investigation of perovskite-based materials and devices. Although electric field-induced PL quenching provides additional useful information, this phenomenon is quite complex and not yet clearly understood. Here, we address the PL quenching of methylammonium lead iodide (MAPbI3) perovskite in a light-emitting diode (PeLED) architecture. We distinguish two quenching mechanisms: (a) indirect quenching by slow irreversible or partially reversible material changes that occur gradually under the applied light and electric field and (b) direct quenching by the influence of the electric field on the charge carrier densities, their spatial distributions, and radiative recombination rates. Direct quenching, observed under the abrupt application of negative voltage, causes a decrease of the PL intensity. However, the PL intensity then partially recovers within tens of milliseconds as mobile ions screen the internal electric field. The screening time increases to hundreds of seconds at low temperatures, indicating activation energies for ion motion of about 80 meV. On the other hand, ultrafast time-resolved PL measurements revealed two main phases of direct quenching: an instantaneous reduction in the radiative carrier recombination rate, which we attribute to the electron and hole displacement within individual perovskite grains, followed by a second phase lasting hundreds of picoseconds, which is due to the charge carrier extraction and spatial separation of electron and hole "clouds" within the entire perovskite layer thickness.

A Simplified Model of Activation and Deactivation of Human Rod Phototransduction-An Electroretinographic Study

Purpose

To test the hypothesis that a simple model having properties consistent with activation and deactivation in the rod approximates the whole time course of the photoresponse.

Methods

Routinely, an exponential of the form f = α·(1 - exp(-(τ·(t - teff)s-1))), with amplitude α, rate constant τ (often scaled by intensity), irreducible delay teff, and time exponent s-1, is fit to the early period of the flash electroretinogram. Notably, s (an integer) represents the three integrating stages in the rod amplification cascade (rhodopsin isomerization, transducin activation, and cGMP hydrolysis). The time course of the photoresponse to a 0.17 cd·s·m-2 conditioning flash (CF) was determined in 21 healthy eyes by presenting the CF plus a bright probe flash (PF) in tandem, separated by interstimulus intervals (ISIs) of 0.01 to 1.4 seconds, and calculating the proportion of the PF a-wave suppressed by the CF at each ISI. To test if similar kinetics describe deactivation, difference of exponential (DoE) functions with common α and teff parameters, respective rate constants for the initiation (I) and quenching (Q) phases of the response, and specified values of s (sI, sQ), were compared to the photoresponse time course.

Results

As hypothesized, the optimal values of sI and sQ were 3 and 2, respectively. Mean ± SD α was 0.80 ± 0.066, I was 7700 ± 2400 m2·cd-1·s-3, and Q was 1.4 ± 0.47 s-1. Overall, r2 was 0.93.

Conclusions

A method, including a DoE model with just three free parameters (α, I, Q), that robustly captures the magnitude and time-constants of the complete rod response, was produced. Only two steps integrate to quench the rod photoresponse.

Investigation of the Interaction between Mechanosynthesized ZnS Nanoparticles and Albumin Using Fluorescence Spectroscopy

In this paper, ZnS nanoparticles were bioconjugated with bovine serum albumin and prepared in a form of nanosuspension using a wet circulation grinding. The stable nanosuspension with monomodal particle size distribution (d50 = 137 nm) and negative zeta potential (-18.3 mV) was obtained. The sorption kinetics and isotherm were determined. Interactions between ZnS and albumin were studied using the fluorescence techniques. The quenching mechanism, describing both static and dynamic interactions, was investigated. Various parameters were calculated, including the quenching rate constant, binding constant, stoichiometry of the binding process, and accessibility of fluorophore to the quencher. It has been found that tryptophan, in comparison to tyrosine, can be closer to the binding site established by analyzing the synchronous fluorescence spectra. The cellular mechanism in multiple myeloma cells treated with nanosuspension was evaluated by fluorescence assays for quantification of apoptosis, assessment of mitochondrial membrane potential and evaluation of cell cycle changes. The preliminary results confirm that the nontoxic nature of ZnS nanoparticles is potentially applicable in drug delivery systems. Additionally, slight changes in the secondary structure of albumin, accompanied by a decrease in α-helix content, were investigated using the FTIR method after analyzing the deconvoluted Amide I band spectra of ZnS nanoparticles conjugated with albumin. Thermogravimetric analysis and long-term stability studies were also performed to obtain a complete picture about the studied system.

Photon- and Singlet-Oxygen-Induced Cis-Trans Isomerization of the Water-Soluble Carotenoid Crocin

Studying the cis-trans isomerization process in crocin (CR), one of the few water-soluble carotenoids extracted from saffron, is important to better understand the physiological role of cis-carotenoids in vivo and their potential as antioxidants in therapeutic applications. For that, cis-trans isomerization of both methanol- and water-dissolved CR was induced by light or thermally generated singlet oxygen (¹O₂). The kinetics of molecular concentrations were monitored by both high-performance liquid chromatography (HPLC) and non-destructive spectrophotometric methods. These last made it possible to simultaneously follow the cis-trans isomerization, the possible bleaching of compounds and the amount of thermally generated ¹O₂. Our results were in accordance with a comprehensive model where the cis-trans isomerization occurs as relaxation from the triplet state of all-trans- or 13-cis-CR, whatever is the way to populate the CR triplet state, either by photon or ¹O₂ energy transfer. The process is much more (1.9 to 10-fold) efficient from cis to trans than vice versa. In H₂O, a ¹O₂-induced bleaching effect on the starting CR was not negligible. However, the CR "flip-flop" isomerization reaction could still occur, suggesting that this process can represent an efficient mechanism for quenching of reactive oxygen species (ROS) in vivo, with a limited need of carotenoid regeneration.

Fluorescent and Magnetic Radical Dendrimers as Potential Bimodal Imaging Probes

Dual or multimodal imaging probes have emerged as powerful tools that improve detection sensitivity and accuracy in disease diagnosis by imaging techniques. Two imaging techniques that are complementary and do not use ionizing radiation are magnetic resonance imaging (MRI) and optical fluorescence imaging (OFI). Herein, we prepared metal-free organic species based on dendrimers with magnetic and fluorescent properties as proof-of-concept of bimodal probes for potential MRI and OFI applications. We used oligo(styryl)benzene (OSB) dendrimers core that are fluorescent on their own, and TEMPO organic radicals anchored on their surfaces, as the magnetic component. In this way, we synthesized six radical dendrimers and characterized them by FT-IR, ¹H NMR, UV-Vis, MALDI-TOF, SEC, EPR, fluorimetry, and in vitro MRI. Importantly, it was demonstrated that the new dendrimers present two properties: on one hand, they are paramagnetic and show the ability to generate contrast by MRI in vitro, and, on the other hand, they also show fluoresce emission. This is a remarkable result since it is one of the very few cases of macromolecules with bimodal magnetic and fluorescent properties using organic radicals as the magnetic probe.

The Efficient Way to Design Cooling Sections for Heat Treatment of Long Steel Products

To achieve the required mechanical properties in the heat treatment of steel, it is necessary to have an adequate cooling rate and to achieve the desired final temperature of the product. This should be achieved with one cooling unit for different product sizes. In order to provide the high variability of the cooling system, different types of nozzles are used in modern cooling systems. Designers often use simplified, inaccurate correlations to predict the heat transfer coefficient, resulting in the oversizing of the designed cooling system or failure to provide the required cooling regime. This typically results in longer commissioning times and higher manufacturing costs of the new cooling system. Accurate information about the required cooling regime and the heat transfer coefficient of the designed cooling is critical. This paper presents a design approach based on laboratory measurements. Firstly, the way to find or validate the required cooling regime is presented. The paper then focuses on nozzle selection and presents laboratory measurements that provide accurate heat transfer coefficients as a function of position and surface temperature for different cooling configurations. Numerical simulations using the measured heat transfer coefficients allow the optimum design to be found for different product sizes.

High-Temperature Behaviour of Zn-Based Galvannealed Coatings on Steel

The potential of using a Zn-based, hot-dip coating to limit steel scale formation was investigated. The phase evolution within a pure Zn and a Zn0.1Al coating on a medium-carbon (0.5 wt.% C, 0.25 wt.% Si) steel sheet during a series of heat treatment steps was investigated. Such Zn-based coatings react with the steel substrate depending on the actual heat treatment condition. A series of expected intermetallic phases was observed via SEM/EDX and XRD techniques, such as ζ, δ and Γ phases along the η(Zn) phase. The η(Zn) phase was transformed to mainly δ and Γ phases during galvannealing (500 °C). The rapid quenching from 850 °C enabled the formation of the supersaturated α-(Fe) solid solution with increased Zn content. A continuous, intact, ~20 µm thick coating was observed after the final step of the heat treatment procedure, while signs of liquid metal embrittlement (LME) were not observed near the coating/steel interface. This will ensure reliable protection against heavy scale formation on heat-treated steel parts.

Quenching-Induced Defect-Rich Platinum/Metal Oxide Catalysts Promote Catalytic Oxidation

Enhancing oxygen activation through defect engineering is an effective strategy for boosting catalytic oxidation performance. Herein, we demonstrate that quenching is an effective strategy for preparing defect-rich Pt/metal oxide catalysts with superior catalytic oxidation activity. As a proof of concept, quenching of α-Fe₂O₃ in aqueous Pt(NO₃)₂ solution yielded a catalyst containing Pt single atoms and clusters over defect-rich α-Fe₂O₃ (Pt/Fe₂O₃-Q), which possessed state-of-the-art activity for toluene oxidation. Structural and spectroscopic analyses established that the quenching process created abundant lattice defects and lattice dislocations in the α-Fe₂O₃ support, and stronger electronic interactions between Pt species and Fe₂O₃ promote the generation of higher oxidation Pt species to modulate the adsorption/desorption behavior of reactants. In situ diffuse reflectance infrared Fourier transform spectroscopy (in situ DRIFTS) characterization studies and density functional theory (DFT) calculations determined that molecular oxygen and Fe₂O₃ lattice oxygen were both activated on the Pt/Fe₂O₃-Q catalyst. Pt/CoMn₂O₄, Pt/MnO₂, and Pt/LaFeO₃ catalysts synthesized by the quenching method also offered superior catalytic activity for toluene oxidation. Results encourage the wider use of quenching for the preparation of highly active oxidation catalysts.

A Novel Quantum Dots-Based Fluorescent Sensor for Determination of the Anticancer Dacomitinib: Application to Dosage Forms

One of the most promising drugs recently approved for the treatment of various types of cancer is dacomitinib, which belongs to the tyrosine kinase inhibitor class. The US Food and Drugs Administration (FDA) has recently approved dacomitinib as a first-line treatment for patients suffering from non-small cell lung cancer (NSCLC) with epidermal growth factor receptor (EGFR) mutations. The current study proposes the design of a novel spectrofluorimetric method for determining dacomitinib based on newly synthesized nitrogen-doped carbon quantum dots (N-CQDs) as fluorescent probes. The proposed method is simple and does not require pretreatment or preliminary procedures. Since the studied drug does not have any fluorescent properties, the importance of the current study is magnified. When excited at 325 nm, N-CQDs exhibited native fluorescence at 417 nm, which was quantitatively and selectively quenched by the increasing concentrations of dacomitinib. The developed method involved the simple and green microwave-assisted synthesis of N-CQDs, using orange juice as a carbon source and urea as a nitrogen source. The characterization of the prepared quantum dots was performed using different spectroscopic and microscopic techniques. The synthesized dots had consistently spherical shapes and a narrow size distribution and demonstrated optimal characteristics, including a high stability and a high fluorescence quantum yield (25.3%). When assessing the effectiveness of the proposed method, several optimization factors were considered. The experiments demonstrated highly linear quenching behavior across the concentration range of 1.0-20.0 μg/mL with a correlation coefficient (r) of 0.999. The recovery percentages were found to be in the range of 98.50-100.83% and the corresponding relative standard deviation (%RSD) was 0.984. The proposed method was shown to be highly sensitive with a limit of detection (LOD) as low as 0.11 μg/mL. The type of mechanism by which quenching took place was also investigated by different means and was found to be static with a complementary inner filter effect. For quality purposes, the assessment of the validation criteria adhered to the ICHQ2(R1) recommendations. Finally, the proposed method was applied to a pharmaceutical dosage form of the drug (Vizimpro^® Tablets) and the obtained results were satisfactory. Considering the eco-friendly aspect of the suggested methodology, using natural materials to synthesize N-CQDs and water as a diluting solvent added to its greenness profile.

A systematic evaluation of quenching and extraction procedures for quantitative metabolome profiling of HeLa carcinoma cell under 2D and 3D cell culture conditions

Metabolic reprogramming has been coined as a hallmark of cancer, accompanied by which the alterations in metabolite levels have profound effects on gene expression, cellular differentiation, and the tumor environment. Yet a systematic evaluation of quenching and extraction procedures for quantitative metabolome profiling of tumor cells is currently lacking. To achieve this, this study is aimed at establishing an unbiased and leakage-free metabolome preparation protocol for HeLa carcinoma cell. We evaluated 12 combinations of quenching and extraction methods from three quenchers (liquid nitrogen, -40°C 50% methanol, 0.5°C normal saline) and four extractants (-80°C 80% methanol, 0.5°C methanol/chloroform/water [1:1:1 v/v/v], 0.5°C 50% acetonitrile, 75°C 70% ethanol) for global metabolite profiling of adherent HeLa carcinoma cells. Based on the isotope dilution mass spectrometry (IDMS) method, gas/liquid chromatography in tandem with mass spectrometry was used to quantitatively determine 43 metabolites including sugar phosphates, organic acids, amino acids (AAs), adenosine nucleotides, and coenzymes involved in central carbon metabolism. The results showed that the total amount of the intracellular metabolites in cell extracts obtained using different sample preparation procedures with the IDMS method ranged from 21.51 to 295.33 nmol per million cells. Among 12 combinations, cells that washed twice with phosphate buffered saline (PBS), quenched with liquid nitrogen, and then extracted with 50% acetonitrile were found to be the most optimal method to acquire intracellular metabolites with high efficiency of metabolic arrest and minimal loss during sample preparation. In addition, the same conclusion was drawn as these 12 combinations were applied to obtain quantitative metabolome data from three-dimensional (3D) tumor spheroids. Furthermore, a case study was carried out to evaluate the effect of doxorubicin (DOX) on both adherent cells and 3D tumor spheroids using quantitative metabolite profiling. Pathway enrichment analysis using targeted metabolomics data showed that DOX exposure would significantly affect AA metabolism-related pathways, which might be related to the mitigation of redox stress. Strikingly, our data suggested that compared to two-dimensional (2D) cells the increased intracellular glutamine level in 3D cells benefited replenishing the tricarboxylic acid (TCA) cycle when the glycolysis was limited after dosing with DOX. Taken together, this study provides a well-established quenching and extraction protocol for quantitative metabolome profiling of HeLa carcinoma cell under 2D and 3D cell culture conditions. Based on this, quantitative time-resolved metabolite data can serve to the generation of hypotheses on metabolic reprogramming to reveal its important role in tumor development and treatment.

Quenching-Induced Defects Liberate the Latent Reversible Capacity of Lithium Titanate Anode

Interest in defect engineering for lithium-ion battery (LIB) materials is sparked by its ability to tailor electrical conductivity and introduce extra active sites for electrochemical reactions. However, harvesting excessive intrinsic defects in the bulk of the electrodes rather than near their surface remains a long-standing challenge. Here, a versatile strategy of quenching is demonstrated, which is exercised in lithium titanate (Li₄ Ti₅ O₁₂ , LTO), a renowned anode for LIBs, to achieve off-stoichiometry in the interior region. In situ synchrotron analysis and atomic-resolution microscopy reveal the enriched oxygen vacancies and cation redistribution after ice-water quenching, which can facilitate the native unextractable Li ions to participate in reversible cycling. The fabricated LTO anode delivers a sustained capacity of 202 mAh g^-1 in the 1.0-2.5 V range with excellent rate capability and overcomes the poor cycling stability seen in conventional defective electrodes. The feasibility of tuning the degree of structural defectiveness via quenching agents is also proven, which can open up an intriguing avenue of research to harness the intrinsic defects for improving the energy density of rechargeable batteries.

Fluorometric Sensing and Detection of p-Nitroaniline by Mixed Metal (Zn, Ni) Tungstate Nanocomposite

Aromatic amines are important chemical intermediates that hold an irreplaceable significance for synthesizing many chemical products. However, they may react with substances excreted from human bodies to generate blood poisoning, skin eczema, and dermatitis disease and even induce cancer-causing high risks to human health and the environment. Metal tungstates have been proven to be highly efficient materials for developing various toxic gases or chemical detection sensor systems. However, the major factors of the sensors, such as sensitivity, selectivity, stability, response, and recovery times, still need to be optimized for practical technological applications. In this work, Ni-doped ZnWO₄ mixed metal tungstate nanocomposite material was synthesized by the hydrothermal method and explored as a sensor for the fluorometric determination of p-nitroaniline (p-NA). Transmission electron microscopy (TEM) was used for the elucidation of the optimized particle diameter. Scanning electron microscopy (SEM) was employed to observe the surface morphological changes in the material during the solid-state reactions. The vibration modes of as-prepared samples were analyzed using Fourier-transform infrared spectroscopy (FTIR). The chemical bonding and oxidation states of individual elements involved in material synthesis were observed using X-ray photoelectron spectroscopy (XPS). The PL activities of the metal tungstate nanoparticles were investigated for the sensing of p-nitroaniline (p-NA). The obtained results demonstrated that ZnNiWO₄ was more effective in sensing p-NA than the other precursors were by using the quenching effect. The material showed remarkably high sensitivity towards p-NA in a concentration range of 25-1000 μM, and the limit of detection (LOD) value was found to be 1.93 × 10^-8 M for ZnWO₄, 2.17 × 10^-8 M for NiWO₄, and 2.98 × 10^-8 M for ZnNiWO₄, respectively.

Applications of fluorescence spectroscopy in protein conformational changes and intermolecular contacts

Emission fluorescence is one of the most versatile and powerful biophysical techniques used in several scientific subjects. It is extensively applied in the studies of proteins, their conformations, and intermolecular contacts, such as in protein-ligand and protein-protein interactions, allowing qualitative, quantitative, and structural data elucidation. This review, aimed to outline some of the most widely used fluorescence techniques in this area, illustrate their applications and display a few examples. At first, the data on the intrinsic fluorescence of proteins is disclosed, mainly on the tryptophan side chain. Predominantly, research to study protein conformational changes, protein interactions, and changes in intensities and shifts of the fluorescence emission maximums were discussed. Fluorescence anisotropy or fluorescence polarization is a measurement of the changing orientation of a molecule in space, concerning the time between the absorption and emission events. Absorption and emission indicate the spatial alignment of the molecule's dipoles relative to the electric vector of the electromagnetic wave of excitation and emitted light, respectively. In other words, if the fluorophore population is excited with vertically polarized light, the emitted light will retain some polarization based on how fast it rotates in solution. Therefore, fluorescence anisotropy can be successfully used in protein-protein interaction investigations. Then, green fluorescent proteins (GFPs), photo-transformable fluorescent proteins (FPs) such as photoswitchable and photoconvertible FPs, and those with Large Stokes Shift (LSS) are disclosed in more detail. FPs are potent tools for the study of biological systems. Their versatility and wide range of colours and properties allow many applications. Finally, the application of fluorescence in life sciences is exposed, especially the application of FPs in fluorescence microscopy techniques with super-resolution that enables precise in vivo photolabeling to monitor the movement and interactions of target proteins.

Molecular recognition of two bioactive coumarin derivatives 7-hydroxycoumarin and 4-methyl-7-hydroxycoumarin by hen egg white lysozyme: Exploring the binding mechanism, thermodynamic parameters and structural changes using multispectroscopic and computational approaches

Multispectroscopic and computational methods of exploring the interaction between a carrier protein and therapeutic compounds provide a preliminary investigation into establishing the efficacy of such compounds. Here, two coumarin derivatives, 7-hydroxycoumarin (7-HC) and 4-methyl-7-hydroxycoumarin (4-Me-7-HC), were selected to carry out numerous biophysical interaction studies with a model carrier protein, hen egg white lysozyme (HEWL). Fluorescence spectroscopy studies conducted between HEWL and 7-HC/4-Me-7-HC revealed the binding constants (K_b) were in the range of 10⁴ M^-1, indicating a moderate nature of binding. The quenching mechanism observed during complexation process was an unusual static quenching due to the effect of temperature on the rate constant. Thermodynamic parameters revealed a positive ΔH and ΔS for HEWL-7-HC/4-Me-7-HC, indicating hydrophobic forces played a dominant role in the interaction process. FRET studies suggested a possible non-radiative energy transfer from the donor (HEWL) to the acceptor (coumarins). Molecular docking studies revealed the interaction of 7-HC/4-Me-7-HC with intrinsic fluorophores, Trp63 and Trp108, Trp108 being an essential residue for binding as proven by molecular dynamic (MD) simulation. MD simulation studies also indicated conformational stability gained by HEWL upon interaction with 7-HC and 4-Me-7-HC. The microenvironment surrounding the Trp residues showed a significant Stoke's shift on carrying out 3-D fluorescence. CD studies revealed a decrease in the alpha helical content of HEWL upon interacting with the ligands. Enzymatic assay conducted for HEWL in the presence of 7-HC/4-Me-7-HC saw an increase in the activity of HEWL, suggesting a change in structural conformation and stability of the protein, altering its activity.Communicated by Ramaswamy H. Sarma.

Grain-Boundary-Induced Ultrasensitive Molecular Detection of Graphene Film

Graphene has been considered a promising platform for molecular detection due to the graphene-enhanced Raman scattering (GERS) effect. However, the GERS performance of pristine graphene is limited by a low chemically active surface and insufficient density of states (DOS). Although diverse defects have been introduced, it remains a great challenge to improve the enhancement performance. Here, we show that graphene grain boundaries (GBs) possess stronger adsorption capacity and more abundant DOS. Thus, GERS performance increases with the atomic percentage of GBs, which makes nanocrystalline graphene (NG) film a superior GERS substrate. For R6G as a probe molecule, a low detection limit of 3 × 10^-10 M was achieved. Utilizing the high chemical activity of GBs, we also fabricated NG film decorated with Au particles using a one-step quenching strategy, and this hybrid film exhibits an extremely low limit of detection down to 5 × 10^-11 M, outperforming all the reported graphene-based systems.

A "Nonsolvent Quenching" Strategy for 3D Printing of Polysaccharide Scaffolds with Immunoregulatory Accuracy

3D printing enables the customized design of implant structures for accurately regulating host responses. However, polysaccharides, as a major biomaterial category with versatile immune activities, are typically "non-printable" due to the collapse of their filaments extruded during printing. This challenge renders their potential as immunomodulatory scaffolds underexploited. Here, inspired by the quench hardening in metal processing, a nonsolvent quenching (NSQ) strategy is innovatively designed for the 3D printing of polysaccharides. Through rapid solvent exchanging, NSQ instantly induces surface hardening to strengthen the polysaccharide filaments upon extrusion, requiring neither chemical modification nor physical blending that alters the material properties. Tested with five polysaccharides with varying physicochemical properties, NSQ prints predesigned structures at organ-relevant scales and a long shelf-life over 3 months. Glucomannan scaffolds, fabricated via NSQ with different grid spacings (1.5 and 2.5 cm), induce distinct host responses upon murine subcutaneous implantation-from specific carbohydrate receptor activation to differential immunocytes accumulation and tissue matrix remodeling-as mechanistically validated in wild-type and Tlr2^-/- knockout mice. Overall, NSQ as a facile and generic strategy is demonstrated to fabricate polysaccharide scaffolds with improved shape fidelity, thereby potentially unmasking their accurate immunomodulatory activities for future biomaterials design.

Selective Sensing of Darolutamide and Thalidomide in Pharmaceutical Preparations and in Spiked Biofluids

Selective spectrofluorometric sensing is introduced for the analysis of non-steroidal anti-androgens, darolutamide, and thalidomide in pharmaceutical preparations and biofluids. An organic fluorophore, 2,4,8,10-tetramethylpyrido[2',3':3,4]pyrazolo[1,5-a]pyrimidine 2 was synthesized in our laboratories by new simple methods to act as a fluorescent reagent for the analysis of the studied drugs. Elemental and spectral analyses were performed to approve the fluorophore structure. The fluorophore possesses a fluorescence at λ_em 422 nm when excited at 328 nm. The interaction between the studied drugs and the fluorophore was found to be quenching. The quenching mechanisms were studied and interpreted through the Stern-Volmer relationship. Moreover, the Stern-Volmer constants were calculated for the quenching interactions of both drugs. The introduced method was validated for the estimation of darolutamide and thalidomide in dosage forms, plasma, and urine, offering good percentage recoveries.

Characterizing Transient Protein-Protein Interactions by Trp-Cys Quenching and Computer Simulations

Transient protein-protein interactions occur frequently under the crowded conditions encountered in biological environments. Tryptophan-cysteine quenching is introduced as an experimental approach with minimal labeling for characterizing such interactions between proteins due to its sensitivity to nano- to microsecond dynamics on subnanometer length scales. The experiments are paired with computational modeling at different resolutions including fully atomistic molecular dynamics simulations for interpretation of the experimental observables and to gain molecular-level insights. This approach is applied to model systems, villin variants and the drkN SH3 domain, in the presence of protein G crowders. It is demonstrated that Trp-Cys quenching experiments can differentiate between overall attractive and repulsive interactions between different proteins, and they can discern variations in interaction preferences at different protein surface locations. The close integration between experiment and simulations also provides an opportunity to evaluate different molecular force fields for the simulation of concentrated protein solutions.

Optical Oxygen Sensors Show Reversible Cross-Talk and/or Degradation in the Presence of Nitrogen Dioxide

A variety of luminescent dyes including the most common indicators for optical oxygen sensors were investigated in regard to their stability and photophysical properties in the presence of nitrogen dioxide. The dyes were immobilized in polystyrene and subjected to NO₂ concentrations from 40 to 5500 ppm. The majority of dyes show fast degradation of optical properties due to the reaction with NO₂. The class of phosphorescent metalloporphyrins shows the highest resistance against nitrogen dioxide. Among them, palladium(II) and platinum(II) complexes of octasubstituted sulfonylated benzoporphyrins are identified as the most stable dyes with almost no decomposition in the presence of NO₂. The phosphorescence of these dyes is reversibly quenched by nitrogen dioxide. Immobilized in various polymeric matrices, the sulfonylated Pt(II) benzoporphyrin demonstrates about one order of magnitude more efficient quenching by NO₂ than by molecular oxygen. Our study demonstrates that virtually all commercially available and reported optical oxygen sensors are likely to show either irreversible decomposition in the presence of nitrogen dioxide or reversible luminescence quenching. They should be used with extreme caution if NO₂ is present in relatively high concentrations or it may be generated from other species such as nitric oxide. As an important consequence of nearly anoxic systems, production of nitrogen dioxide or nitric oxide may be therefore erroneously interpreted as an increase in oxygen concentration.

Spectroscopic strategies for quantitation of varenicline in pharmaceutical preparations and content uniformity testing

Herein, two new facile methods were examined for varenicline determination using erythrosine. The latter is a food additive that has been recently investigated as a fluorescent dye for the determination of drugs. In the first method, the fluorescence of erythrosine B was quenched quantitatively by increasing the concentration of varenicline through ion-pair complex formation. This linear response was a basis for the spectrofluorimetric method used for varenicline quantitation in pure and dosage forms. The quenching is correlated with the concentration linearly over the range of 0.4-4.0 µg ml^-1 at 550 nm after excitation at 528 nm with a correlation coefficient of 0.9993. Different parameters were investigated to reach the optimal conditions with the highest sensitivity and repeatability. The second method is depending on measuring the formed complex by spectrophotometry at 550 nm over the range of 1.0-10.0 µg ml^-1 with an excellent correlation coefficient of 0.9999. The suggested methods were validated consistently with ICH guidelines, with acceptable results. The procedures were used to test the uniformity of content of Champix tablets. By comparing with the previous spectroscopic method, there was no significant difference as revealed from the calculated Student t-test and variance ratio F-test values.

A Perspective on the Use of Fluorescent Imaging to Reveal Mechanisms of Breakup

Purpose: Tear film instability, which can lead to rapid tear film breakup (TBU), is considered to be a major etiological factor in dry eye. However, experimental support for many of the proposed theories for TBU mechanisms is relatively scarce. The major aim of this perspective is to show that fluorescence studies of TBU can be used to provide experimental evidence for two proposed underlying mechanisms of TBU, evaporation and divergent flow.Methods: To understand the effects of TBU on tear film fluorescence, we show that local fluorescence is the product of three main factors: tear film thickness, fluorescein concentration and fluorescent efficiency. In divergent tear flow, tear film thickness is reduced without change in fluorescein concentration and fluorescent efficiency, thus leading to reduced fluorescence intensity. Evaporation causes decreased fluorescence mainly by self-quenching due to high fluorescein concentration. Fluorescent efficiency is reduced by quenching at high fluorescein concentration but is independent of concentration for very low fluorescein concentration; thus, comparison of high and very low concentrations of fluorescein can be used to discriminate between divergent flow and evaporation. Finally, it is shown how the fluorescent pattern can change greatly during the development of breakup.Conclusions: This analysis demonstrates that the study of tear film fluorescence in TBU and dry eye may be underutilized as additional information pertinent to clinical practice may be obtained. A better understanding of TBU mechanisms may lead to improved diagnosis and treatment of dry eye.

Reaching Nearly 100% Quantum Efficiencies in Thin Solid Films of Semiconducting Polymers via Molecular Confinements under Large Segmental Stresses

Quantum efficiencies remain a critical issue for general applications of semiconducting polymers in optoelectronics and others. In this work, we demonstrate that nearly 100% quantum efficiencies (η's) in thin solid films can be reached when the polymer molecules are mechanically stretched into molecular confinement. We selected three conjugated polymers of varied backbone stiffness and interchain coupling, prepared in both diluted and pristine states. All of the polymers when highly diluted (c = 0.1 wt %) exhibited massive η increases after stretching to very large strains (∼300-500%) via micronecking, with the rigid polyfluorene (PFO) and semirigid MEH-PPV both manifesting η ≈ 90%, while the most flexible yet regioregular polythiophene (P3HT-rr) exhibited a 10-fold increase to ∼21%. In the pristine state, molecular aggregation and interchain coupling curtail development of the molecular confinement, but the large-strain deformation still enhances η's significantly, to ∼90% (PFO) and ∼55% (MEH-PPV) despite no increases for the crystalline P3HT-rr. Moreover, upon substitution by a bulkier side-group to reduce interchain coupling, the pristine films of polythiophene (P3EHT) exhibited a ∼3-fold increase of η after the stretching. The nearly 100% of η's in fully stretched molecules indicates that the in situ self-trapping occurring via sub-picosecond backbone interactions can be mostly responsible for energy dissipations and quite suppressible by segmental stress control. The mechanical confinement effects also indicate the fundamental role of molecular mechanics during stabilization and migration of photoexcited charges.

Study of Oligonucleotides Access and Distribution in Human Peripheral Blood Mononuclear Cells

Therapeutic oligonucleotides have achieved great clinical interest since their approval as drug agents by regulatory agencies but their access and distribution in blood cells are not completely known. We evaluated by flow cytometry the ability of short fluorescent scramble oligonucleotides (ON*) to access human peripheral blood mononuclear cells (PBMC) after incubating with ON* during 1 h and 7 days of culture follow-up 'in vitro'. Blood samples were treated with chemically modified oligonucleotides (phosphorothioate backbone and 2' O-Me ends) to resist nuclease digestion under culture conditions. The ON* internalization was determined after discarding the membrane-associated fluorescence by trypan blue quenching. Whereas the oligonucleotide accessed neutrophils and monocytes rapidly, achieving their maximum in 1 h and 24 h, respectively, lymphocytes required 7 days to achieve the maximum (80% of cells) transfection. The ON*ability to access lymphocyte types (T, B, and NK) and T cell subtypes (CD4+, CD8+, and CD4-CD8-) were similar, with T cells being more accessible. Regulatory CD4+ and CD8+ T cells were classified in low and high Foxp3 expressers, whose expression proved not to alter the ON* internalization during the first hour, achieving 53% of CD4+Foxp3+ and 40% of CD8+Foxp3+ cells. Our results contribute to understanding and improving the management of therapeutic ONs.

Effects of Elevated Temperature on the Residual Behavior of Concrete Containing Marble Dust and Foundry Sand

Concrete is a composite material that is commonly used in the construction industry. It will certainly be exposed to fires of varying intensities when used in buildings and industries. The major goal of this article was to look into the influence of mineral additions such as foundry sand and marble dust on the residual characteristics of concrete. To examine the behavior of residual characteristics of concrete after fire exposure, marble dust was substituted for cement and fine sand was substituted for foundry sand in varying amounts ranging from 0% to 20%. It aided in the better disposal of waste material so that it might be used as an addition. The purpose of the experiment was to see how increased temperatures affected residual properties of concrete, including flexural strength, compressive strength, tensile strength, static as well as dynamic elastic modulus, water absorption, mass loss, and ultrasonic pulse velocity. At temperatures of 200 °C, 400 °C, 600 °C, 800 °C, and 1000 °C, the typical fire exposure behavior of concrete was investigated. The effects of two cooling techniques, annealing and quenching, on the residual properties of concrete after exposure to high temperatures were investigated in this study. Replacement of up to 10% of the cement with marble dust and fine sand with foundry sand when concrete is exposed to temperatures up to 400 °C does not influence the behavior of concrete. At temperatures above 400 °C, however, the breakdown of concrete, which includes marble dust and foundry sand, causes a rapid deterioration in the residual properties of concrete, primarily for replacement of more than 10%.

Association Mechanism and Conformational Changes in Trypsin on Its Interaction with Atrazine: A Multi- Spectroscopic and Biochemical Study with Computational Approach

Atrazine (ATR) is a herbicide globally used to eliminate undesired weeds. Herbicide usage leads to various adverse effects on human health and the environment. The primary source of herbicides in humans is the food laced with the herbicides. The ATR binding to trypsin (TYP) was investigated in this study to explore its binding potential and toxicity. In vitro interaction of ATR with TYP was studied using multi-spectroscopic methods, molecular docking, and enzyme kinetics to explore the mechanism of binding for the TYP-ATR system. The TYP-ATR complex revealed binding constants (10³ M^-1), suggesting a moderate binding. The free energy for the TYP-ATR complexes was negative, suggesting a spontaneous interaction. Thermodynamic parameters enthalpy (ΔH) and entropy (ΔS) obtained positive values for the TYP-ATR system suggesting hydrophobic interactions in the binding process. Micro-environmental and conformational changes in TYP molecules were induced on interaction with ATR. Reduced catalytic activity of TYP was observed after interaction with ATR owing to the changes in the secondary structure of the TYP.

Graphitic-phase C3N4 nanosheets combined with MnO2 nanosheets for sensitive fluorescence quenching detection of organophosphorus pesticides

In this study, we have developed a sensitive approach to measure organophosphorus pesticides (OPs) using graphitic-phase C₃N₄ nanosheets (g-C₃N₄) combined with a nanomaterial-based quencher, MnO₂ nanosheets (MnO₂ NS). Since MnO₂ NS can quench the fluorescence of g-C₃N₄ via the inner-filter effect (IFE), enzymatic hydrolysate (thiocholine, TCh) can efficiently trigger the decomposition of MnO₂ nanosheets in the presence of acetylcholinesterase (AChE) and acetylthiocholine (ATCh), resulting in the fluorescence recovery of g-C₃N₄. OPs, as inhibitors to AChE activity, can prevent the generation of TCh and decomposition of MnO₂ nanosheets while exhibiting fluorescence quenching. Therefore, the AChE-ATCh-MnO₂-g-C₃N₄ system can be utilized to quantitatively detect OPs based on g-C₃N₄ fluorescence. Under optimal conditions, the linear ranges for the determination of parathion-methyl (PM) and 2,2-dichlorovinyl dimethyl phosphate (DDVP) were found to be 0.1-2.1 ng/mL and 0.5-16 ng/mL, respectively, with limits of detection of 0.069 ng/mL and 0.20 ng/mL, respectively. The advantages of this assay are user-friendliness, ease of use, and cost effectiveness compared to other more sophisticated analytical instruments.

Experimental Study on the Quenching Behavior of a Copper Cube in the Cellulose Nanofiber Solution

This study investigates the quenching behavior and heat transfer characteristics of a copper cube immersed in cellulose nanofiber (CNF) solutions. The heat transfer performance of CNF solutions during boiling has been examined in several studies, but the quenching behavior of CNF solutions, which is an important heat transfer method, has not been evaluated. In this study, four copper cubes with the same dimensions and four different quenchants (deionized water and 0.01%, 0.1% and 0.5% CNF solutions) were prepared. A copper cube heated to greater than 600 °C was submerged three times in the quenchant. This was repeated with different copper cubes in each of the quenchants. The time at which the heated copper cube convectively transferred heat to the surroundings was recorded. The cooling time was shortest when the cube was immersed in a 0.5% CNF solution for the first time. The average cooling time for quenching in the 0.5% CNF solution was 30.3% shorter than that in DI water. In this study, film boiling during quenching was thoroughly observed and analyzed to explain the cause of enhancement in heat transfer efficiency.

Reusable and pH-Stable Luminescent Sensors for Highly Selective Detection of Phosphate

Phosphate sensors have been actively studied owing to their importance in water environment monitoring because phosphate is one of the nutrients that result in algal blooms. As with other nutrients, seamless monitoring of phosphate is important for understanding and evaluating eutrophication. However, field-deployable phosphate sensors have not been well developed yet due to the chemical characteristics of phosphate. In this paper, we report on a luminescent coordination polymer particle (CPP) that can respond selectively and sensitively to a phosphate ion against other ions in an aquatic ecosystem. The CPPs with an average size of 88.1 ± 12.2 nm are embedded into membranes for reusable purpose. Due to the specific binding of phosphates to europium ions, the luminescence quenching behavior of CPPs embedded into membranes shows a linear relationship with phosphate concentrations (3-500 μM) and detection limit of 1.52 μM. Consistent luminescence signals were also observed during repeated measurements in the pH range of 3-10. Moreover, the practical application was confirmed by sensing phosphate in actual environmental samples such as tap water and lake water.

Quenching as a Route to Defect-Rich Ru-Pyrochlore Electrocatalysts toward the Oxygen Evolution Reaction

Defects have a significant impact on the electrocatalysts performance. Introducing defect structures in metal oxides such as pyrochlores and perovskites has proved to be an effective strategy to enhance electrocatalytic activity. However, it is hard to build numerous defect sites in such high-temperature oxides due to the strong metal-oxygen bonds and the so-called self-purification effect, which becomes increasingly important as the particle size reduced to the nanoscale. Here, a facile strategy is demonstrated to fabricate defect-rich yttrium ruthenate oxides Y₂ Ru₂ O_{7- δ} with the pyrochlore structure (denoted D_rich -YRO) by the liquid nitrogen (<-196 °C) quenching. Owing to the almost instantaneous cooling in oxygen-deficient condition, a large number of defects-including oxygen vacancies, grain boundaries, pores and surficial disorder-are preserved in the room temperature material and act as electrocatalytic active sites for oxygen evolution. As a result, D_rich -YRO shows excellent catalytic activity and high electrochemical stability, along with a high performance in the operation of proton exchange membrane electrolyzer. The quenching strategy employed in this work provides a facile approach for constructing defect-rich structures in high-temperature oxides and should lead to new applications in energy conversion and storage devices for such materials.

Inner Filter Effect as a Boon in Perovskite Sensing Systems to Achieve Higher Sensitivity Levels

Perovskite quantum dots (PQDs) exhibit exceptional fluorescence property and are potential candidates for fluorescent metal-ion sensors. The present work shows the presence of inner filter effect (IFE) in perovskite sensing systems and its significance in enhancing the detection limits. Two different sensing systems (with a different extent of IFE), one with simple long-chain monodentate ligand-capped PQDs and the other with short-chain bidentate ligand capped PQDs, were developed toward sensing Co²⁺. The fluorescence quenching mechanism is elucidated and is observed to be a combination of Forster resonance energy transfer (FRET) and IFE. The electrostatic interaction of donor (D) with acceptor (A) and its distance for energy transfer was appropriate and was well within the requirement for a good energy transfer from PQDs (donor) to Co²⁺ ions (acceptor) facilitating partial FRET. Also, the spectral overlap of absorption of excited and emitted radiation (of PQDs) with that of Co²⁺ allows a significant amount of IFE. PQDs were successfully modified for lesser spectral overlap with reduced IFE. The reduction in IFE adversely drops the detection levels from 0.733 × 10^-7 to 0.7970 × 10^-6 on modification. This work provides insights into the design and development of high sensing perovskite probes with manipulation of IFE and also shows the importance of IFE to be considered during the study of such sensing systems, which has been neglected so far in perovskite systems.

Improved Sample Preparation for Untargeted Metabolomics Profiling of Escherichia coli

Metabolomics is a powerful tool that can systematically describe global changes in the metabolome of microbes, thus improving our understanding of the mechanisms of action of antibiotics and facilitating the development of next-generation antibacterial therapies. However, current sample preparation methods are not efficient or reliable for studying the effects of antibiotics on microbes. In the present study, we reported a novel sample preparation approach using cold methanol/ethylene glycol for quenching Escherichia coli, thus overcoming the loss of intracellular metabolites caused by cell membrane damage. After evaluating the extraction efficiency of several extraction methods, we employed the optimized workflow to profile the metabolome of E. coli exposed to cephalexin. In doing so, we proved the utility of the proposed approach and provided insights into the comprehensive metabolic alterations associated with antibiotic treatment.

IMPORTANCE The emergence and global spread of multidrug-resistant bacteria and genes are a global problem. It is critical to understand the interactions between antibiotics and bacteria and find alternative treatments for infections when we are moving closer to a postantibiotic era. It has been demonstrated that the bacterial metabolic environment plays an important role in the modulation of antibiotic susceptibility and efficacy. In the present study, we proposed a novel metabolomic approach for intracellular metabolite profiling of E. coli, which can be used to investigate the metabolite alterations of bacteria caused by antibiotic treatment. Further understanding of antibiotic-induced perturbations of bacterial metabolism would facilitate the discovery of new therapeutic targets and pathways.

Study on the Compressive Stress Retention in Quenched Cam of 100Cr6 Steel Based on Coupled Thermomechanical and Metallurgical Modeling

The assembled camshaft has obvious advantages in material optimization and flexible manufacturing. As the most important surface modification technique, the heat treatment process is utilized in this work to promote the desired compressive residual stress on the near-surface of the 100Cr6 steel assembled cam. The Johnson-Mehl-Avrami equation and Koistinen-Marbuger law are integrated into the ABAQUS software via user subroutines to simulate the evolution of diffusional transformation and diffusionless transformation, respectively. The linear mixture law is used for describing the coupled thermomechanical and metallurgical behaviors in the quenching of steel cam. The influences of various quenchants and the probable maximum phase volume fractions on surface residual stress or hardness are analyzed. Results show that a greater amount of martensite volume fraction and a slower martensitic transformation rate are beneficial for the compressive stress retention. Compared with the conventional quenching oil, the fast oil quenched cam surface has higher final compressive stress and hardness.

Detection of Heavy Metals in Water Using Graphene Oxide Quantum Dots: An Experimental and Theoretical Study

In this work, we investigate by ab initio calculations and optical experiments the sensitivity of graphene quantum dots in their use as devices to measure the presence, and concentration, of heavy metals in water. We demonstrate that the quenching or enhancement in the optical response (absorption, emission) depends on the metallic ion considered. In particular, two cases of opposite behaviour are considered in detail: Cd2+, where we observe an increase in the emission optical response for increasing concentration, and Pb2+ whose emission spectra, vice versa, are quenched along the concentration rise. The experimental trends reported comply nicely with the different hydration patterns suggested by the models that are also capable of reproducing the minor quenching/enhancing effects observed in other ions. We envisage that quantum dots of graphene may be routinely used as cheap detectors to measure the degree of poisoning ions in water.

Top-Down N-Doped Carbon Quantum Dots for Multiple Purposes: Heavy Metal Detection and Intracellular Fluorescence

In the present study, we successfully synthesized N-doped carbon quantum dots (N-CQDs) using a top-down approach, i.e., hydroxyl radical opening of fullerene with hydrogen peroxide, in basic ambient using ammonia for two different reaction times. The ensuing characterization via dynamic light scattering, SEM, and IR spectroscopy revealed a size control that was dependent on the reaction time, as well as a more pronounced -NH2 functionalization. The N-CQDs were probed for metal ion detection in aqueous solutions and during bioimaging and displayed a Cr3+ and Cu2+ selectivity shift at a higher degree of -NH2 functionalization, as well as HEK-293 cell nuclei marking.

Influence of Various Heat Treatments on Hardness and Impact Strength of Uddeholm Balder: Cr-Mo-V-Ni Novel Steel Used for Engine Construction

The construction of an engine requires optimized geometry and superb material properties in various environments. Tensile and yield strength are not the only parameters essential to consider. Hardness, impact toughness, and ductile-brittle transition temperature (DBTT) are also crucial. In this paper, Balder, Chromium-Molybdenum-Vanadium-Nickel steel with low impact toughness attested is considered. It contains both high Nickel and high Vanadium content, a rare combination among iron-based alloys. This study aims at proving that conventional heat treatment can improve its impact toughness while maintaining hardness level, exceeding its to-date performance. Steel’s exact elemental composition was checked, and material samples’ hardness and impact toughness were measured. Four heat treatments were proposed, then hardness and impact toughness were measured again. It was established that impact toughness over three times higher than marketed (57.3 J against 17 J) can be achieved with simultaneous 2 HRC points (from 46.4 HRC to 48.4 HRC) rise in hardness. Achieved parameters place examined alloy at the high-ranking position among similar steels. Occurrence of temper embrittlement was avoided. Notably, the ductile-brittle transition was not observed in any sample.

Quenching Behavior of the Electrochemiluminescence of Ru(bpy)32+ /TPrA System by Phenols on a Smartphone-Based Sensor

Phenolic compounds such as vanillic and p-coumaric acids are pollutants of major concern in the agro-industrial processing, thereby their effective detection in the industrial environment is essential to reduce exposure. Herein, we present the quenching effect of these compounds on the electrochemiluminescence (ECL) of the Ru(bpy)32+ /TPrA (TPrA=tri-n-propylamine) system at a disposable screen-printed carbon electrode. Transient ECL profiles are obtained from multiple video frames following 1.2 V application by a smartphone-based ECL sensor. A wide range of detection was achieved using the sensor with limit of detection of 0.26 μM and 0.68 μM for vanillic and p-coumaric acids, respectively. The estimated quenching constants determined that the quenching efficiency of vanillic acid is at least two-fold that of p-coumaric acid under the current detection conditions. The present ECL quenching approach provided an effective method to detect phenolic compounds using a low-cost, portable smartphone-based ECL sensor.

Surface Plasmon-Assisted Fluorescence Enhancing and Quenching: From Theory to Application

The integration of surface plasmon resonance and fluorescence yields a multiaspect improvement in surface fluorescence sensing and imaging, leading to a paradigm shift of surface plasmon-assisted fluorescence techniques, for example, surface plasmon enhanced field fluorescence spectroscopy, surface plasmon coupled emission (SPCE), and SPCE imaging. This Review aims to characterize the unique optical property with a common physical interpretation and diverse surface architecture-based measurements. The fundamental electromagnetic theory is employed to comprehensively unveil the fluorophore-surface plasmon interaction, and the associated surface-modification design is liberally highlighted to balance the surface plasmon-induced fluorescence-enhancement efforts and the surface plasmon-caused fluorescence-quenching effects. In particular, all types of surface structures, for example, silicon, carbon, protein, DNA, polymer, and multilayer, are systematically interrogated in terms of component, thickness, stiffness, and functionality. As a highly interdisciplinary and expanding field in physics, optics, chemistry, and surface chemistry, this Review could be of great interest to a broad readership, in particular, among physical chemists, analytical chemists, and in surface-based sensing and imaging studies.

Ultrasensitive and selective detection of Hg2+ using fluorescent phycocyanin in an aqueous system

Hg²⁺ toxicity is one of the most common chemical poisonings that occurs mainly from drinking polluted water. In the current work, Phycocyanin (PC) was exploited as a fluorescent sensor for sensitive and selective detection of Hg²⁺ in an aqueous system. PC-Hg²⁺ interaction was monitored using a spectro-fluorometer under different buffered solutions at pH values of 6,7,8,9, or 10 above the isoelectric point of PC (5.18). A remarkable decrease of PC fluorescence intensity was observed under Tris-buffer at pH 6 upon the addition of increasing Hg²⁺ concentrations (1-120 nM). Under the maintained experimental conditions, the current sensor showed a good linear relationship with R² = 0.9971 and a limit of detection as low as 0.7 nM was achieved. In addition, a notable selectivity of Hg²⁺ over other nine heavy metals (Cu^2+, Zn^2+, Pb²⁺, Mg^2+, Mn⁴⁺, Li⁺, Fe^3+, Co²⁺, and Al³⁺) was achieved in the presence of 120 nM of each metal. Moreover, the current fluorescent detection assay was also tested in real samples of pond water, and recoveries as well as relative standard deviations within the acceptable limits were recorded.

Computational Study of Quenching Effects on Growth Processes and Size Distributions of Silicon Nanoparticles at a Thermal Plasma Tail

In this paper, quenching effects on silicon nanoparticle growth processes and size distributions at a typical range of cooling rates in a thermal plasma tail are investigated computationally. We used a nodal-type model that expresses a size distribution evolving temporally with simultaneous homogeneous nucleation, heterogeneous condensation, interparticle coagulation, and melting point depression. The numerically obtained size distributions exhibit similar size ranges and tendencies to those of experiment results obtained with and without quenching. In a highly supersaturated state, 40–50% of the vapor atoms are converted rapidly to nanoparticles. After most vapor atoms are consumed, the nanoparticles grow by coagulation, which occurs much more slowly than condensation. At higher cooling rates, one obtains greater total number density, smaller size, and smaller standard deviation. Quenching in thermal plasma fabrication is effectual, but it presents limitations for controlling nanoparticle characteristics.

Fluorescence Study of Riboflavin Interactions with Graphene Dispersed in Bioactive Tannic Acid

The potential of tannic acid (TA) as a dispersing agent for graphene (G) in aqueous solutions and its interaction with riboflavin have been studied under different experimental conditions. TA induces quenching of riboflavin fluorescence, and the effect is stronger with increasing TA concentration, due to π-π interactions through the aromatic rings, and hydrogen bonding interactions between the hydroxyl moieties of both compounds. The influence of TA concentration, the pH, and the G/TA weight ratio on the quenching magnitude, have been studied. At a pH of 4.1, G dispersed in TA hardly influences the riboflavin fluorescence, while at a pH of 7.1, the nanomaterial interacts with riboflavin, causing an additional quenching to that produced by TA. When TA concentration is kept constant, quenching of G on riboflavin fluorescence depends on both the G/TA weight ratio and the TA concentration. The fluorescence attenuation is stronger for dispersions with the lowest G/TA ratios, since TA is the main contributor to the quenching effect. Data obey the Stern–Volmer relationship up to TA 2.0 g L⁻¹ and G 20 mg L⁻¹. Results demonstrate that TA is an effective dispersant for graphene-based nanomaterials in liquid medium and a green alternative to conventional surfactants and synthetic polymers for the determination of biomolecules.

New Insight into the Fluorescence Quenching of Nitrogen-Containing Carbonaceous Quantum Dots-From Surface Chemistry to Biomedical Applications

Carbon-based quantum dots are widely suggested as fluorescent carriers of drugs, genes or other bioactive molecules. In this work, we thoroughly examine the easy-to-obtain, biocompatible, nitrogen-containing carbonaceous quantum dots (N-CQDs) with stable fluorescent properties that are resistant to wide-range pH changes. Moreover, we explain the mechanism of fluorescence quenching at extreme pH conditions. Our in vitro results indicate that N-CQDs penetrate the cell membrane; however, fluorescence intensity measured inside the cells was lower than expected from carbonaceous dots extracellular concentration decrease. We studied the mechanism of quenching and identified reduced form of β-nicotinamide adenine dinucleotide (NADH) as one of the intracellular quenchers. We proved it experimentally that the elucidated redox process triggers the efficient reduction of amide functionalities to non-fluorescent amines on carbonaceous dots surface. We determined the 5 nm-wide reactive redox zone around the N-CQD surface. The better understanding of fluorescence quenching will help to accurately quantify and dose the internalized carbonaceous quantum dots for biomedical applications.