A stepwise surface ionization method for ion mobility spectrometry.

RATIONALE: The detection of organic nitrogen compounds in exhaled breath is expected to provide an early warning of diseases such as kidney disease. Detecting these trace disease markers in exhaled breath with complex composition and high moisture content is a challenge. Surface ionization (SI) shows a highly selective ionization of organic nitrogen compounds, and it is a good candidate for breath analysis combined with ion mobility spectrometry (IMS). METHODS: A stepwise SI method of low-temperature adsorption/high-temperature ionization was proposed, and trimethylamine (TMA) was detected when combined with an ion mobility spectrometer. TMA at different concentrations and humidity levels and spiked in human breath was detected to evaluate the method's properties. RESULTS: TMA with concentrations from 2 to 200 ppb was detected. The peak intensity of the TMA characteristic ions was linearly related to the "e" exponent of the concentration with a curve fit of 0.996. A standard deviation of less than 0.306% was obtained with 10 replicate analyses of 10 ppb TMA. The signal intensity difference between dry and wet (relative humidity > 93%) TMA samples is only 2.7%, and the recovery rate of the sample was 106.819%. CONCLUSIONS: SI-IMS based on the stepwise SI method has the advantages of low ionization temperature, high detection sensitivity, strong resistance to humidity interference, and good repeatability. It is a promising method for detecting organic nitrogen compounds in exhaled breath.

Mango Leaves (Mangifera indica)-Derived Highly Florescent Green Graphene Quantum Dot Nanoprobes for Enhanced On-Off Dual Detection of Cholesterol and Fe2+ Ions Based on Molecular Logic Operation.

In the present study, we have engineered a molecular logic gate system employing both Fe2+ ions and cholesterol as bioanalytes for innovative detection strategies. We utilized a green-synthesis method employing the mango leaves extract to create fluorescent graphene quantum dots termed "mGQDs". Through techniques like HR-TEM, i.e., high-resolution transmission electron microscopy, Raman spectroscopy, and XPS, i.e., X-ray photoelectron spectroscopy, the successful formation of mGQDs was confirmed. The photoluminescence (PL) characteristics of mGQDs were investigated for potential applications in metal ion detection, specifically Fe2+ traces in water, by using fluorescence techniques. Under 425 nm excitation, mGQDs exhibited emission bands at 495 and 677 nm in their PL spectrum. Fe2+-induced notable quenching of mGQDs' PL intensity decreased by 97% with 2.5 µM Fe2+ ions; however, adding 20 mM cholesterol resulted in a 92% recovery. Detection limits were established through a linear Stern-Volmer (S-V) plot at room temperature, yielding values of 4.07 µM for Fe2+ ions and 1.8 mM for cholesterol. Moreover, mGQDs demonstrated biocompatibility, aqueous solubility, and nontoxicity, facilitating the creation of a rapid nonenzymatic cholesterol detection method. Selectivity and detection studies underscored mGQDs' reliability in cholesterol level monitoring. Additionally, a molecular logic gate system employing Fe2+ metal ions and cholesterol as a bioanalyte was established for detection purposes. Overall, this research introduces an ecofriendly approach to craft mGQDs and highlights their effectiveness in detecting metal ions and cholesterol, suggesting their potential as versatile nanomaterials for diverse analytical and biomedical applications.

Novel benzothiazole-pyrazoline-styrene hybrid for ultrasensitive detection of Hg(II) ions: Synthesis and chemosensor evaluation.

Water pollution has become a serious issue, and mercury(II) ion (Hg(II)) is highly toxic even at low concentrations. Therefore, Hg(II) concentration should be strictly monitored. This study evaluated pyrazoline compounds as fluorescence chemosensor agents for Hg(II) detection. These compounds were prepared from vanillin via etherification, Claisen-Schmidt, and cyclocondensation reactions, to yield benzothiazole-pyrazoline-styrene hybrid compounds. The hybrid compound without styrene was successfully synthesized in 97.70% yield with limit of detection (LoD) and limit of quantification (LoQ) values of 323.5 and 1078 µM, respectively. Conversely, the hybrid compound was produced in 97.29% yield with the LoD and LoQ values of 8.94 and 29.79 nM, respectively. Further spectroscopic investigations revealed that Hg(II) ions can either chelate with three nitrogen of pyridine, pyrazoline, and benzothiazole structures or two oxygen of vanillin and styrene. Furthermore, the hybrid compound was successfully applied in the direct quantification of Hg(II) ions in tap and underground water samples with a validity of 91.63% and 86.08%, respectively, compared with mercury analyzer measurement. The regeneration of pyrazoline was also easily achieved via the addition of an ethylenediaminetetraacetic acid solution. These findings show the promising application of the benzothiazole-pyrazoline-styrene hybrid compound for Hg(II) monitoring in real environmental samples.

Fluorescent aptasensors for sensitive detection of lead ions based on structure-switching DNA beacon probe and exonuclease I-mediated signal amplification.

Herein, two simple fluorescent signal-on sensing strategies for detecting lead ions (Pb2+) were established based on structure-switching aptamer probes and exonuclease-assisted signal amplification strategies. Two hairpin-structure fluorescent probes with blunt-ended stem arms were designed by extending the base sequence of Pb2+ aptamer (PS2.M) and labelling the probes with FAM (in probe 1) and 2-aminopurine (2-AP) (in probe 2), respectively. In method 1, graphene oxide (GO) was added to adsorb probe 1 and quench the fluorescence emission of FAM to achieve low fluorescent background. In method 2, fluorescent 2-AP molecule inserted into the double-stranded DNA of probe 2 was quenched as a result of base stacking interactions, leading to a simplified, quencher-free approach. The addition of Pb2+ can induce the probes to transform into G-quadruplex structures, exposing single DNA strands at the 3' end (the extended sequences). This exposure enables the activation of exonuclease I (Exo I) on the probes, leading to the cleavage effect and subsequent release of free bases and fluorophores, thereby resulting in amplified fluorescence signals. The two proposed methods exhibit good specificity and sensitivity, with detection limits of 0.327 nM and 0.049 nM Pb2+ for method 1 and method 2, respectively, and have been successfully applied to detect Pb2+ in river water and fish samples. Both detection methods employ the structure-switching aptamer probes and can be completed in two or three steps without the need for complex analytical instruments. Therefore, they have a broad prospect in the sensitive and simple detection of lead ion contamination in food and environmental samples.

Flexible electronics for heavy metal ion detection in water: a comprehensive review.

Flexible electronics offer a versatile, rapid, cost-effective and portable solution to monitor water contamination, which poses serious threat to the environment and human health. This review paper presents a comprehensive exploration of the versatile platforms of flexible electronics in the context of heavy metal ion detection in water systems. The review overviews of the fundamental principles of heavy metal ion detection, surveys the state-of-the-art materials and fabrication techniques for flexible sensors, analyses key performance metrics and limitations, and discusses future opportunities and challenges. By highlighting recent advances in nanomaterials, polymers, wireless integration, and sustainability, this review aims to serve as an essential resource for researchers, engineers, and policy makers seeking to address the critical challenge of heavy metal contamination in water resources. The versatile promise of flexible electronics is thoroughly elucidated to inspire continued innovation in this emerging technology arena.

Quantitative Analysis of Blended Oils Based on Intensity Ratios of Marker Ions in MALDI-MS Spectra.

Determination of quantitative compositions of blended oils is an essential but challenging step for the quality control and safety assurance of blended oils. We herein report a method for the quantitative analysis of blended oils based on the intensity ratio of triacylglycerol marker ions, which could be obtained from the highly reproducible spectra acquired by using matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) to directly analyze blended oils in their oily states. We demonstrated that this method could provide good quantitative results to binary, ternary, and quaternary blended oils, with simultaneous quantitation of multiple compositions, and was applicable for quantitative analysis of commercial blended oil products. Moreover, the intensity ratio-based method could be used to rapidly measure the proportions of oil compositions in blended oils, only based on the spectra of the blended oils and related pure oils, making the method as a high-throughput approach to meet the sharply growing analytical demands of blended oils.

A New Fluorene-Based Fluorescent Probe for Recognition of Hypochlorite Ions and its Applications.

Oxidative stress is a trigger for many diseases and occurs with the unstable hypochlorite (ClO-), known as one of the reactive oxygen species (ROS) in organisms. Then, HOCI is acknowledged as an oxidizing species that eliminates a variety of environmental pollutants. Hence, the development of novel methodologies for the selective and precise identification of HOCl/ ClO- is considered to be of utmost importance. In this study, the design, characterization, and applications of a fluorene-based fluorescent probe (FHBP) dependent on the ESIPT mechanism with a "turn-on" response for the sensitive/selective determination of ClO- against other competing samples were reported. The experimental results indicated that the detection limit for ClO-could be quantitatively determined by the probe to be 8.2 × 10-7 M. The binding constant of the probe FHBP with ClO- was computed as 9.75 × 103 M-1. In addition, the response time of FHBP was appointed to be 30 s, indicating a rapid reaction with ClO-. It has also been demonstrated that this probe can be successfully used for the detection of ClO- on filter papers, TLC sheets, cotton swabs, and real samples.

A highly sensitive and selective fluorescent "on-off-on" peptide-based probe for sequential detection of Hg2+ and S2- ions: Applications in living cells and zebrafish imaging.

Mercury ions (Hg2+) and sulfur ions (S2-), have caused serious harm to the ecological environment and human health as two kinds of highly toxic pollutants widely used. Therefore, the visual quantitative determination of Hg2+ and S2- is of great significance in the field of environmental monitoring and medical therapy. In this study, a novel fluorescent "on-off-on" peptide-based probe DNC was designed and synthesized using dipeptide (Asn-Cys-NH2) as the raw material via solid phase peptide synthesis (SPPS) technology with Fmoc chemistry. DNC displayed high selectivity in the recognition of Hg2+, and formed non-fluorescence complex (DNC-Hg2+) through 2:1 binding mode. Notably, DNC-Hg2+ complex generated in situ was used as relay response probe for highly selective sequential detection of S2- through reversible formation-separation. DNC achieved highly sensitive detection of Hg2+ and S2- with the detection limits (LODs) of 8.4 nM and 5.5 nM, respectively. Meanwhile, DNC demonstrated feasibility for Hg2+ and S2- detections in two water samples, and the considerable recovery rate was obtained. More importantly, DNC showed excellent water solubility and low toxicity, and was successfully used for consecutive discerning Hg2+ and S2- in test strips, living cells and zebrafish larvae. As an effective visual analysis method in the field, smartphone RGB Color Picker APP realized semi-quantitative detections of Hg2+ and S2- without the need for complicated device.

Gábor Transform-Based Signal Isolation, Rapid Deconvolution, and Quantitation of Intact Protein Ions with Mass Spectrometry.

High-resolution mass spectrometry (HRMS) is a powerful technique for the characterization and quantitation of complex biological mixtures, with several applications including clinical monitoring and tissue imaging. However, these medical and pharmaceutical applications are pushing the analytical limits of modern HRMS techniques, requiring either further development in instrumentation or data processing methods. Here, we demonstrate new developments in the interactive Fourier-transform analysis for mass spectrometry (iFAMS) software including the first application of Gábor transform (GT) to protein quantitation. Newly added automation tools detect signals from minimal user input and apply thresholds for signal selection, deconvolution, and baseline correction to improve the objectivity and reproducibility of deconvolution. Additional tools were added to improve the deconvolution of highly complex or congested mass spectra and are demonstrated here for the first time. The "Gábor Slicer" enables the user to explore trends in the Gábor spectrogram with instantaneous ion mass estimates accurate to 10 Da. The charge adjuster allows for easy visual confirmation of accurate charge state assignments and quick adjustment if necessary. Deconvolution refinement utilizes a second GT of isotopically resolved data to remove common deconvolution artifacts. To assess the quality of deconvolution from iFAMS, several comparisons are made to deconvolutions using other algorithms such as UniDec and an implementation of MaxEnt in Agilent MassHunter BioConfirm. Lastly, the newly added batch processing and quantitation capabilities of iFAMS are demonstrated and compared to a common extracted ion chromatogram approach.

A thiazole-based colorimetric and photoluminescent chemosensors for As3+ ions detection: Density functional theory, test strips, real samples, and bioimaging applications.

A Schiff-base Ethyl (E)-2-(3-((2-carbamothioylhydrazono)methyl)-4-hydroxyphenyl)-4-methylthiazole-5-carboxylate (TZTS) dual functional colorimetric and photoluminescent chemosensor which includes thiazole and thiosemicarbazide has been synthesized to detect arsenic (As3+) ions selectively in DMSO: H2O (7:3, v/v) solvent system. The molecular structure of the probe was characterized via FT-IR, 1H, and 13C NMR & HRMS analysis. Interestingly, the probe exhibits a remarkable and specific colorimetric and photoluminescence response to As3+ ions when exposed to various metal cations. The absorption spectral changes of TZTS were observed upon the addition of As3+ ions, with a naked eye detectable color change from colorless to yellow color. Additionally, the chemosensor (TZTS) exhibited a new absorption band at 412 nm and emission enhancements in photoluminescence at 528 nm after adding As3+ ions. The limit of detection (LOD) for As3+ ions was calculated to be 16.5 and 7.19 × 10-9 M by the UV-visible and photoluminescent titration methods, respectively. The underlying mechanism and experimental observations have been comprehensively elucidated through techniques such as Job's plot, Benesi-Hildebrand studies, and density functional theory (DFT) calculations. For practical application, the efficient determination of As3+ ions were accomplished using a spike and recovery approach applied to real water samples. In addition, the developed probe was successfully employed in test strip applications, allowing for the naked-eye detection of arsenic ions. Moreover, fluorescence imaging experiments of As3+ ions in the breast cancer cell line (MCF-7) demonstrated their practical applications in biological systems. Consequently, these findings highlight the significant potential of the TZTS sensor for detecting As3+ ions in environmental analysis systems.

A label-free photoelectrochemical biosensor for silver ions based on Zn-Co doped C and CdS QD nanomaterials.

A sensitive photoelectrochemical (PEC) biosensor for silver ions (Ag+) was developed based on Zn-Co doped C and CdS quantum dot (CdS QD) nanomaterials. Hydrophobic modified sodium alginate (HMA), which could stabilize and improve the PEC performance of CdS QDs, was also used for the construction of PEC sensors. Especially, Zn-Co doped C, CdS QDs and HMA were sequentially modified onto an electrode surface via the drop-coating method, and a C base rich DNA strand was then immobilized onto the modified electrode. As the C base in DNA specifically recognized Ag+, it formed a C-Ag+-C complex in the presence of Ag+, which created a spatial steric hindrance, resulting in a reduced PEC response. The sensing platform is sensitive to Ag+ in the range of 10.0 fM to 0.10 µM, with a limit of detection of 3.99 fM. This work offers an ideal platform to determine trace heavy metal ions in environmental monitoring and bioanalysis.

Fluorescent Protein-Based Sensors for Detecting Essential Metal Ions across the Tree of Life.

Genetically encoded fluorescent metal ion sensors are powerful tools for elucidating metal dynamics in living systems. Over the last 25 years since the first examples of genetically encoded fluorescent protein-based calcium indicators, this toolbox of probes has expanded to include other essential and non-essential metal ions. Collectively, these tools have illuminated fundamental aspects of metal homeostasis and trafficking that are crucial to fields ranging from neurobiology to human nutrition. Despite these advances, much of the application of metal ion sensors remains limited to mammalian cells and tissues and a limited number of essential metals. Applications beyond mammalian systems and in vivo applications in living organisms have primarily used genetically encoded calcium ion sensors. The aim of this Perspective is to provide, with the support of historical and recent literature, an updated and critical view of the design and use of fluorescent protein-based sensors for detecting essential metal ions in various organisms. We highlight the historical progress and achievements with calcium sensors and discuss more recent advances and opportunities for the detection of other essential metal ions. We also discuss outstanding challenges in the field and directions for future studies, including detecting a wider variety of metal ions, developing and implementing a broader spectral range of sensors for multiplexing experiments, and applying sensors to a wider range of single- and multi-species biological systems.

Construction of a novel flavonol fluorescent probe for copper (II) ion detection and its application in actual samples.

Copper is an essential trace element in the human body, and its level is directly related to many diseases. While the source of copper in human body is mainly intake from food, then the detection of copper ions (Cu2+) in food becomes crucial. Here, we synthesized a novel probe (E)-3-hydroxy-2-styryl-4H-benzo[h]chromen-4-one (NSHF) and explored the binding ability of NSHF for Cu2+ using nuclear magnetic resonance hydrogen spectroscopy (1H NMR), high-resolution mass spectrometry (HRMS), Job's plot method and density functional theory (DFT). NSHF shows the advantages of fast response time, good selectivity and high sensitivity for Cu2+. The fluorescence intensity ratio (F/F0) of NSHF shows a good linear relationship with the concentration of Cu2+ and the detection limit is 0.061 µM. NSHF was successfully applied to the detection of Cu2+ in real samples. In addition, a simple and convenient Cu2+ detection platform was constructed by combining NSHF with a smartphone and a UV lamp, which can realize the rapid detection of Cu2+. This work provides an effective tool for the real-time detection of Cu2+.

Theoretical and experimental study on the effect of scanning speed on FAIMS peaks.

High-Field Asymmetric Ion Mobility Spectrometry (FAIMS) is a technique for ion separation and detection based on ion mobility variation under high electronic field. While compensation voltage scanning speed is a fundamental parameter in FAIMS, its impact on spectra remains unclear. In this work, a function referred to as F-EMG is introduced to describe the impact of compensation voltage scanning speed on FAIMS spectra, and the properties of the function are studied. Theoretical analysis emphasizes the impact of the scanning speed on peak height, position, and symmetry, as well as the capability of the F-EMG function to progressively approach Gaussian function at lower scanning speeds. Furthermore, the function indicates that spectra obtained in positive and negative scanning modes exhibits symmetry. An experimental validation, conducted with a custom FAIMS setup and analyzing hydrogen sulfide, ethylbenzene, toluene, styrene, benzene and ammonia, confirms the model's influence on peak features, fitting accuracy, and exhibits a closer alignment with the Gaussian function at lower scanning speeds. Additionally, the experimental data indicate that the spectra show symmetry in positive and negative scanning models. This work not only improves understanding of FAIMS spectral analysis but also introduces a robust method for enhancing data accuracy across varying scanning speeds.

A colorimetric and fluorescent probe of lignocellulose nanofiber composite modified with Rhodamine 6G derivative for reversible, selective and sensitive detection of metal ions in wastewater.

Heavy metal ions have extremely high toxicity. As the top of food chain, human beings certainly will accumulate them by ingesting food and participating other activities, which eventually result in the damage to our health. Therefore, it is very meaningful and necessary to design a simple, portable, stable and efficient material for heavy metal ions detection. Based on the spirolactam Rhodamine 6G (SRh6G) fluorescent probe, we prepared two types of nanocomposite materials (membrane and aerogel) by vacuum filtration and freeze-drying methods with lignocellulose nanofiber (CNF) as a carrier, polyvinyl alcohol (PVA) and glutaraldehyde (GA) as the cross-linkers. Then the microstructure, chemical composition, wetting property, fluorescence intensity and selectivity of as-prepared SRh6G/PVA/CNF would be characterized and analyzed. Results showed that SRh6G/PVA/CNF nanocomposites would turn red in color under strong acidic environment and produced orange fluorescence under ultraviolet light. Besides, they were also to detect Al3+, Cu2+, Hg2+, Fe3+ and Ag+ through color and fluorescence variations. We had further tested its sensitivity, selectivity, adsorption, fluorescence limits of detection (LOD) to Fe3+ and Cu2+. The test towards real water samples (hospital wastewater, Songhua River and tap water) proved that SRh6G/PVA/CNF nanocomposites could detect the polluted water with low concentrations of Fe3+ and Cu2+. In addition, SRh6G/PVA/CNF nanocomposites have excellent mechanical property, repeatability, superhydrophilicity and underwater superoleophobicity, which may offer a theoretical reference for the assembly strategy and detection application of cellulose-based fluorescent probe.

Heterocyclic fluorescent Schiff base chemosensors for the detection of Fe(III) and Cu(II) ions.

Two new Schiff bases were synthesized from 1-(2,4-dihydroxyphenyl)ethanone and pyridine derivatives. Both compounds were characterized using infrared, UV-Vis., 1H NMR, 13C NMR and mass spectral studies. Density functional theory (DFT) calculations were performed for both the Schiff bases with 6-31G(d, p) as the basis set. Vibrational frequencies calculated using the theoretical method were in good agreement with the experimental values. Both the Schiff bases were highly fluorescent in nature. The cation-recognizing profile of the compounds was investigated in aqueous methanol medium. The Schiff base 4-(1-(pyridin-4-ylimino)ethyl)benzene-1,3-diol (PYEB) was found to interact with Fe(III) and Cu(II) ions, whereas the Schiff base 4,4'-((pyridine-2,3-diylbis(azanylylidene))bis(ethan-1-yl-1-ylidene))bis(benzene-1,3-diol) (PDEB) was found to detect Cu(II) ions. The mechanism of recognition was established as combined excited state intramolecular proton transfer (ESIPT)-chelation-enhanced fluorescence (CHEF) effect and chelation-enhanced quenching (CHEQ) process for the detection of Fe(III) and Cu(II) ions, respectively. The stability constant of the metal complexes formed during the sensing process was determined. The limit of detection for Fe(III) and Cu(II) ions with respect to Schiff base PYEB was found to be 1.64 × 10-6 and 2.16 × 10-7 M, respectively. With respect to Schiff base PDEB, the limit of detection for Cu(II) ion was found to be 4.54 × 10-4 M. The Cu(II) ion sensing property of the Schiff base PDEB was applied in bioimaging studies for the detection of HeLa cells.

Spatio-seasonal patterns and sources of major ions in the Longjiang River catchment, Southern China.

River water quality is closely related to the major ion sources and hydrological conditions. However, there is a limited cognition about the geochemical sources and the seasonal variations of major ions. Thus, in this study, a total of 90 water samples were collected from the Longjiang River and its three tributaries in the dry and wet seasons. The samples were analyzed, including major ion concentrations and physicochemical parameters. Statistical analysis, such as correlation analysis and principal component analysis (PCA), was employed to investigate the spatial and seasonal variations in major ion composition and their respective sources. Our study revealed that the predominant major ions in the studied samples are Ca2+, Mg2+, HCO - 3, and SO2 - 4. Most of ions exhibited notable spatial disparities attributable to variations in geological settings and human activities. Regions characterized by igneous rock outcrops tend to exhibit higher levels of K+ and Na+, while areas with higher population densities in the middle and downstream segments show elevated concentrations of Cl-, NO - 3, SO2 - 4, Na+, and K+. The observed peak SO2 - 4 levels may be attributed to active mining operations. Most parameters displayed higher values in flood season than those in dry season due to dilution effects. Stoichiometric analysis indicated that carbonate weathering inputs contribute to over 85% of the mean total cation concentrations in the water, followed by contributions from silicates, atmospheric deposition, and anthropogenic inputs. On the whole, although the water quality remains non-polluted and is suitable for drinking and irrigation purposes, the enrichment of SO2 - 4 and NO - 3 may contribute to water eutrophication. Caution is warranted during the dry season due to reduced water flow resulting from dam interceptions and limited dilution capacity, potentially leading to elevated pollutant concentrations. Taken together, our results provided a scientific basis for water quality managements of monsoon rivers.

A fluorescent chemosensor for selective detection of chromium (III) ions in environmentally and biologically relevant samples.

A simple single step one pot multicomponent reaction was performed to synthesize N-(tert-butyl)-2-(furan-2-yl)imidazo[1,2-a]pyridine-3-amine (TBFIPA). The synthesized TBFIPA was subjected to library of cations to study its ability for selective and sensitive detection of specific metal ions. Selective detection of chromium ions by TBFIPA were found from the significant hypsochromic shift (335 nm â†’ 285 nm) in the UV-Visible spectra. The fluorescent TBFIPA displays complete quenching of fluorescence under UV lamp (365 nm) only in the presence of chromium without the interference of common metal ions. Binding constant (ka) obtained from Benesi-Hildebrand plot is 0.21 × 105 M-1, limit of detection (LOD) and limit of quantification (LOQ) of TBFIPA toward Cr3+ ions are 4.70 × 10-7 M and 1.56 × 10-7 M, respectively. The mechanism proposed during complex formation were supported by stoichiometric Job continuous variation plot, 1H NMR titration and ESI-MS spectroscopic data. All the experimental confirmation for complex formation were corroborated with theoretical DFT studies optimized using RB3LYP/6-31G(d) basis set. The selectivity and sensitivity of TBFIPA toward Cr3+ ions are found suitable to design a user-friendly silica based portable test kit. Alongside, TBFIPA was successfully utilized for imaging onion epidermal cells. Furthermore, the results obtained for biological, environmental, and industrial samples provided solid evidence to estimate chromium ions using TBFIPA in these real samples.

Innovative assembled optode device for enhanced in-situ ceric ions (Ce4+) evaluation and preconcentration in its real human, foods, water, and alloy samples.

Cerium (Ce) are the most widely distributed rare earth element. However, humans exposed to Ce through inhalation have been reported to experience heat sensitivity, itching, and heightened taste and odour perception. The present study aims to develop an optical sensor device with a short response time and high selectivity for Ce amongst other ions in various environments. The potential applicability of a 6-hydroxy-5-((4-hydroxy-2-methylphenyl)diazenyl)pyrimidine-2,4(1H,3H)-dione (HHMDPD) assembled ligand as aceric ion (Ce4+)-selective caption optode was examined. After generating an ion pair with Tetra-n-octylammonium bromide (TOABr) and immobilizing on a tri-acetyl cellulose (TAC) membrane, the solubility of the HHMDPD ligand is improved. The constructed optode membrane reacts with Ce4+ by turning its orange colour to violet in Thiel buffer (pH of 5.5), which can be detected spectrophotometrically at λmax 667 nm. The measurement linearity was in the range of 0.70 - 18.7 × 10-6 mol/L of Ce4+ concentration with detection and quantification limits of 0.23 × 10-6 and 0.70 × 10-6 mol/L, respectively. Whatever the Ce4+ concentration in its real samples, the response time of the constructed device was 5.0 min. Additionally, it recorded repeatability and reproducibility with a %RSD of 1.37 and 2.55, respectively (n = 3). The proposed optode device exhibited complete reversibility, for multiple measurements, which could be easily achieved with the aid of a solution of HCl, 0.01 mol/L. The applicability of the proposed device has been effectively extended to analyze synthetic mixes corresponding to different Ce4+ real human, foods, water, and magnesium-based Ce4+ alloys.

The structure and physical properties of a packaged bacteriophage particle.

A string of nucleotides confined within a protein capsid contains all the instructions necessary to make a functional virus particle, a virion. Although the structure of the protein capsid is known for many virus species1,2, the three-dimensional organization of viral genomes has mostly eluded experimental probes3,4. Here we report all-atom structural models of an HK97 virion5, including its entire 39,732 base pair genome, obtained through multiresolution simulations. Mimicking the action of a packaging motor6, the genome was gradually loaded into the capsid. The structure of the packaged capsid was then refined through simulations of increasing resolution, which produced a 26 million atom model of the complete virion, including water and ions confined within the capsid. DNA packaging occurs through a loop extrusion mechanism7 that produces globally different configurations of the packaged genome and gives each viral particle individual traits. Multiple microsecond-long all-atom simulations characterized the effect of the packaged genome on capsid structure, internal pressure, electrostatics and diffusion of water, ions and DNA, and revealed the structural imprints of the capsid onto the genome. Our approach can be generalized to obtain complete all-atom structural models of other virus species, thereby potentially revealing new drug targets at the genome-capsid interface.