Species In Aqueous Solution Research Articles

Short DNAzymes for Efficient Catalysis of "Click" Reactions in Solution and on Surface.

We have systematically investigated and found surprising superior catalytic activities of very short DNAzymes for copper(I)-catalyzed azide-alkyne cycloaddition (CuAAC), both in solution and on surface. As a key reaction of the "click chemistry" class, CuAAC is a highly efficient and specific covalent conjugation tool with demonstrated applications in organic synthesis, bioconjugation, and surface functionalization; however, it requires the presence of the Cu(I) catalyst, which is an unstable species in aqueous solutions. We show here that one ultrashort, 14-nucleotide-truncated fragment of an earlier in vitro selected DNAzyme (CLICK-17) shows a striking and superior catalytic activity toward the in trans CuAAC reaction in solution and on surface in the presence of either Cu(I) or Cu(II), at significantly lowered concentrations. These results obviate the need for long-sequence DNAzymes, selected out of the homogeneous solution phase, for application in complex surface environments.

Lysis-Free Isolation and Direct Amplification of Pathogenic Bacterial DNA Using Diatom Frustules.

DNA has been implicated as an important biomarker for the diagnosis of bacterial infections. Herein, we developed a streamlined methodology that uses diatom frustules (DFs) to liberate and capture bacterial DNA and allows direct downstream amplification tests without any lysis, washing, or elution steps. Unlike most conventional DNA isolation methods that rely on cell lysis to release bacterial DNA, DFs can trigger the oxidative stress response of bacterial cells to promote bacterial membrane vesicle formation and DNA release by generating reactive oxygen species in aqueous solutions. Due to the hierarchical porous structure, DFs provided high DNA capture efficiency exceeding 80% over a wide range of DNA amounts from 10 pg to 10 ng, making only 10 μg DFs sufficient for each test. Since laborious liquid handling steps are not required, the entire DNA sample preparation process using DFs can be completed within 3 min. The diagnostic use of this DF-based methodology was illustrated, which showed that the DNA of the pathogenic bacteria in serum samples was isolated by DFs and directly detected using polymerase chain reaction (PCR) at concentrations as low as 102 CFU/mL, outperforming the most used approaches based on solid-phase DNA extraction. Furthermore, most of the bacterial cells were still alive after DNA isolation using DFs, providing the possibility of recycling samples for storage and further diagnosis. The proposed DF-based methodology is anticipated to simplify bacterial infection diagnosis and be broadly applied to various medical diagnoses and biological research.

Multi-responsive luminescent complex for Fe3+, Cr2O72− and CrO42− species in aqueous solution based on aromatic polycarboxylic acid and imidazole-containing ligand: synthesis, crystal structure and selective detection

One Cadmium(II)-based complex, [Cd(LBIX)(HEA)]n (1), was synthesized using 4,4′-bis((1H-imidazol-1-yl)methyl)-1,1′-biphenyl (LBIX) and 1,2-phenylenediacetic acid (H2HEA) as ligands. The analysis of the single crystal structure reveals that 1 possesses a ladder-like chain structure, which extends into a 3D architecture through π···π interactions. 1 was identified through powder X-ray diffraction analysis (PXRD), elemental analysis (EA), infrared spectroscopy (IR) and thermogravimetric analysis (TGA). It can be seen from the luminescence experiment that 1 has high Ksv value (Cr2O72−: 1.51 × 104 M−1, CrO42−: 1.16 × 104 M−1 and Fe3+: 1.26 × 104 M−1) and lower detection limit (Cr2O72−: 1.14 μM, CrO42−: 1.88 μM and Fe3+: 1.14 μM), it is utilized as a multi-response sensor to recognition Fe3+, CrO42− and Cr2O72− in an aqueous solution. Mechanisms in which fluorescence quenching occurs have been examined using techniques such as PXRD, UV–vis absorption spectra, scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). Due to its excellent selectivity, high sensitivity and strong stability, it is suitable for detecting Fe3+, CrO42− and Cr2O72− ions as a fluorescent probe.

Comparative Analysis of Donnan Steric Partitioning Pore Model and Dielectric Exclusion Applied to the Fractionation of Aqueous Saline Solutions through Nanofiltration

The aim of this study was to analyze, both theoretically and experimentally, the material transport mechanisms governing the separation of ionic species in aqueous solutions using nanofiltration membranes. To interpret the experimental results, the Donnan Steric Partitioning Model (DSPM) and the Dielectric Exclusion Model (DSPM-DE) were applied and computationally simulated in Matlab. Experimental tests were conducted using a pilot-scale system with commercial NF90 membranes. The results indicate that the DSPM better describes the rejection of monovalent ions (sodium and chloride), while the DSPM-DE is more suitable for divalent ions (sulfate and magnesium). Additionally, both models were sensitized to explore the impact of hindrance factors on the rejection of different ionic species. For neutral molecules present in the solution, it was observed that the DSPM and DSPM-DE do not adequately interpret selectivity, suggesting that under such conditions, the electrostatic exclusion mechanism loses significance, with the steric mechanism prevailing.

"Off-Label Use" of the Siderophore Enterobactin Enables Targeted Imaging of Cancer with Radioactive Ti(IV).

The development of inert, biocompatible chelation methods is required to harness the emerging positron emitting radionuclide 45Ti for radiopharmaceutical applications. Herein, we evaluate the Ti(IV)-coordination chemistry of four catechol-based, hexacoordinate chelators using synthetic, structural, computational, and radiochemical approaches. The siderophore enterobactin (Ent) and its synthetic mimic TREN-CAM readily form mononuclear Ti(IV) species in aqueous solution at neutral pH. Radiolabeling studies reveal that Ent and TREN-CAM form mononuclear complexes with the short-lived, positron-emitting radionuclide 45Ti(IV), and do not transchelate to plasma proteins in vitro and exhibit rapid renal clearance in naïve mice. These features guide efforts to target the 45Ti isotope to prostate cancer tissue through the design, synthesis, and evaluation of Ent-DUPA, a small molecule conjugate composed of a prostate specific membrane antigen (PSMA) targeting peptide and a monofunctionalized Ent scaffold. The [45Ti][Ti(Ent-DUPA)]2- complex forms readily at room temperature. In a tumor xenograft model in mice, selective tumor tissue accumulation (8±5 %, n=5), and low off-target uptake in other organs is observed. Overall, this work demonstrates targeted imaging with 45Ti(IV), provides a foundation for advancing the application of 45Ti in nuclear medicine, and reveals that Ent can be repurposed as a 45Ti-complexing cargo for targeted nuclear imaging applications.

“Off‐Label Use” of the Siderophore Enterobactin Enables Targeted Imaging of Cancer with Radioactive Ti(IV)

AbstractThe development of inert, biocompatible chelation methods is required to harness the emerging positron emitting radionuclide 45Ti for radiopharmaceutical applications. Herein, we evaluate the Ti(IV)‐coordination chemistry of four catechol‐based, hexacoordinate chelators using synthetic, structural, computational, and radiochemical approaches. The siderophore enterobactin (Ent) and its synthetic mimic TREN‐CAM readily form mononuclear Ti(IV) species in aqueous solution at neutral pH. Radiolabeling studies reveal that Ent and TREN‐CAM form mononuclear complexes with the short‐lived, positron‐emitting radionuclide 45Ti(IV), and do not transchelate to plasma proteins in vitro and exhibit rapid renal clearance in naïve mice. These features guide efforts to target the 45Ti isotope to prostate cancer tissue through the design, synthesis, and evaluation of Ent‐DUPA, a small molecule conjugate composed of a prostate specific membrane antigen (PSMA) targeting peptide and a monofunctionalized Ent scaffold. The [45Ti][Ti(Ent‐DUPA)]2− complex forms readily at room temperature. In a tumor xenograft model in mice, selective tumor tissue accumulation (8±5 %, n=5), and low off‐target uptake in other organs is observed. Overall, this work demonstrates targeted imaging with 45Ti(IV), provides a foundation for advancing the application of 45Ti in nuclear medicine, and reveals that Ent can be repurposed as a 45Ti‐complexing cargo for targeted nuclear imaging applications.

The accuracy limit of chemical shift predictions for species in aqueous solution.

Interpreting NMR experiments benefits from first-principles predictions of chemical shifts. Reaching the accuracy limit of theory is relevant for unambiguous structural analysis and dissecting theoretical approximations. Since accurate chemical shift measurements are based on using internal reference compounds such as trimethylsilylpropanesulfonate (DSS), a detailed comparison of experimental with theoretical data requires simultaneous consideration of both target and reference species ensembles in the same solvent environment. Here we show that ab initio molecular dynamics simulations to generate liquid-state ensembles of target and reference compounds, including explicitly their short-range solvation environments and combined with quantum-mechanical solvation models, allows for predicting highly accurate 1H (∼0.1-0.5 ppm) and aliphatic 13C (∼1.5 ppm) chemical shifts for aqueous solutions of the model compounds trimethylamine N-oxide (TMAO) and N-methylacetamide (NMA), referenced to DSS without any system-specific adjustments. This encompasses the two peptide bond conformations of NMA identified by NMR. The results are used to derive a general-purpose guideline set for predictive NMR chemical shift calculations of NMA in the liquid state and to identify artifacts of force field models. Accurate predictions are only obtained if a sufficient number of explicit water molecules is included in the quantum-mechanical calculations, disproving a purely electrostatic model of the solvent effect on chemical shifts.

Structure prediction of physiological bis(amino acidato)copper(II) species in aqueous solution: The copper(II) compounds with l-glutamine and l-histidine

Neutral (l-histidinato)(l-glutaminato)copper(II) [Cu(His)(Gln)] has been established as the most abundant ternary copper(II) amino acid compound of the exchangeable copper(II) pool in blood plasma. The experimental studies of Cu(His)(Gln) and bis(glutaminato)copper(II) [Cu(Gln)2] in solutions did not specify their complete geometries. To determine the geometries, this paper investigates the conformers, energy landscapes, and a structure–magnetic parameters relation of Cu(Gln)2 and Cu(His)(Gln) by the density functional theory (DFT) calculations. We assume a glycine-like coordination of Gln (other coordination patterns are dismissed because of steric reasons), and three His in-plane copper(II) binding modes. The conformational analyses are performed in the gas phase and implicitly modeled aqueous solution. The reliability of the DFT relative electronic and Gibbs free energies of the Cu(His)(Gln) conformers is confirmed by benchmarking against the corresponding energies obtained by the domain-based local pair natural orbital coupled-cluster method with singles, doubles, and perturbative triples [DLPNO-CCSD(T)]. Several cis- and trans-Cu(His)(Gln) conformers with His in the histaminate-like and glycine-like modes have low Gibbs free energies, and the greatest estimated metal-binding affinities. The DFT-calculated magnetic parameters of the low-energy conformers reproduce best the experimental electron paramagnetic resonance parameters measured in aqueous solutions for trans- and cis-Cu(Gln)2 conformers having two oxygen atoms (either from Gln or water molecules) at the apical positions, and Cu(His)(Gln) conformers having His in the histaminate-like mode with an apically placed carboxylato oxygen atom. The predicted conformational flexibility of His‑copper(II)-amino acid compounds may be connected with their physiological abundance, and the role in copper(II) exchange reactions in blood plasma.

The effects of amino acid functionalisation on the optoelectronic properties and self-assembly of perylene bisimides

Here we report on ten water-soluble perylene bisimides that are functionalised with the amino acids L-alanine, L-aspartic acid, L-glutamic acid, L-phenylalanine, L-histidine, L-leucine, L-methionine, L-valine, L-tryptophan, and L-tyrosine. Reduction potentials, absoprtion and emission spectra, molar absorptivity, quantum yield, and rheology are obtained and the data interpreted for each species in aqueous solution or hydrogels in order to provide a comprehensive understanding of the subtle effects of amino acid functionalisation on the optoelectronic and supramolecular properties.

Chemodosimetric discriminative analysis of cyanide, ammonia, aliphatic amine, and hydrazine utilizing the diverse reaction types of the pyrylium salt

Pyrylium salts are well known to react with different nucleophiles to form many different types of products like pyridinium salt, pyridine, cyanodienone, thiopyrylium, isoxazoline, N-aminopyridinium salt or 1,2-diazepine, depending on the nucleophile used. This property of pyrylium salts could be used to develop a multi-analyte chemosensor for the species having nucleophilic character. On this idea, we synthesized a pyrylium compound (PyrSen) bearing auxochromes and studied its photophysical responses to different nucleophiles. Different absorption spectra were observed to emerge upon the separate addition of cyanide, propylamine, ammonia, and hydrazine to the aqueous solution of PyrSen (ethanol-water 5:1). In the solutions containing ammonia and hydrazine were also observed fluorescence at different wavelengths. The products responsible for these photophysical properties were isolated and characterized. The developed sensor was proved to be usable for the discrimination and quantification of these four species in aqueous solutions.

Effect of boric acid on 106Ru radionuclide speciation in aqueous solutions

Effect of boric acid on 106Ru radionuclide speciation in aqueous solutions

Comment on “Thermodynamic Data for Sn(IV) Species in Aqueous Solution: Matter of Controversy and Error”

Comment on “Thermodynamic Data for Sn(IV) Species in Aqueous Solution: Matter of Controversy and Error”

Insights into Mn loaded carbon-silica-membrane based catalytic ozonation process for efficient wastewater treatment: Performance and mechanism

Heterogeneous catalytic ozonation (HCO) is a promising technology for advanced wastewater treatment, and developing catalysts with both high catalytic activity and easy recycling capability is challenging but essential. In this work, easily separable Mn loaded carbon–silica-membrane (Mn-CSM) was synthesized by electrospinning and Mn-CSM based packed bed reactor was constructed for catalytic ozonation, achieving excellent catalytic performance for refractory organic degradation. Mn-CSM exhibited a lamellar structure with a thickness of several hundred micrometers and was centimeter-sized in the other two dimensions, which make it easy to be separated in wastewater treatment. At the microscopic scale, Mn-CSM was composed of highly connected nanofibers, which provided large specific surface area for the exposure of active sites. In oxalic acid (OA) degradation and coal gasification wastewater advanced treatment, Mn-CSM demonstrated superior catalytic ozonation performance. After 60 min, 93% of OA was degraded in Mn-CSM based HCO process, and the effluent COD of coal gasification wastewater decreased from 105 mg L−1 to 42 mg L−1. Reactive oxygen species in aqueous solution and on catalyst surface contributed to the organic degradation. The introduction of SiO2 nanoparticles in Mn-CSM can not only enhance its catalytic stability, but also improve fluid flow field distribution. Furthermore, the presence of SiO2 increased the hydrophilicity of Mn-CSM and a better removal of hydrophilic substances (HIS) was achieved in Mn-CSM based HCO. This study highlights a Mn-CSM ozone catalyst with high catalytic activity and easy recycling capability and a Mn-CSM based catalytic ozonation process, which is promising for the degradation of refractory organics in wastewater.

Chemical equilibria in aqueous solutions of H[AuCl4] and bovine or human serum albumin

Interaction of metals with serum albumins is of special interest as it may mediate the toxic or beneficial action of metal ions and their complexes that are often considered (pro)drugs. Among metals, gold(III) draws special attention because of the antibacterial activity of its complexes reported recently. The paper focuses on the interactions between bovine and human serum albumins and gold(III) species in aqueous solutions. Tetrachloroaurate(III) hydrolysis, protein self-association and interactions involving chloride ions are accounted for to determine the most probable stoichiometric composition of gold(III) associated with proteins and the related binding constants. The data obtained are used to calculate the equilibrium composition of the solution containing [AuCl4]−, biologically active hydrazone derived from pyridoxal 5′-phosphate and bovine serum albumin at different pH values.

Rotating Disk Electrodes beyond the Levich Approximation: Physics-Informed Neural Networks Reveal and Quantify Edge Effects.

Physics-informed neural networks are used to characterize the mass transport to the rotating disk electrode (RDE), the most widely employed hydrodynamic electrode in electroanalysis. The PINN approach was first quantitatively verified via 1D simulations under the Levich approximation for cyclic voltammetry and chronoamperometry, allowing comparison of the results with finite difference simulations and analytical equations. However, the Levich approximation is only accurate for high Schmidt numbers (Sc > 1000). The PINN approach allowed consideration of smaller Sc, achieving an analytical level of accuracy (error <0.1%) comparable with independent numerical evaluation and confirming that the errors in the Levich equation can be as high as 3% when Sc = 1000 for rapidly diffusing species in aqueous solution. Entirely novel, the PINNs permit the solution of the 2D diffusion equation under cylindrical geometry incorporating radial diffusion and reveal the rotating disk electrode edge effect as a consequence of the nonuniform accessibility of the disc with greater currents flowing near the extremities. The contribution to the total current is quantified as a function of the rotation speed, disk radius, and analyte diffusion coefficient. The success in extending the theory for the rotating disk electrode beyond the Levich equation shows that PINNs can be an easier and more powerful substitute for conventional methods, both analytical and simulation based.

Modeling phase equilibria and speciation in aqueous solutions of rare earth elements with hydroxide and organic ligands

A thermodynamic model has been developed for calculating speciation and phase equilibria in aqueous solutions of rare earth elements (REEs) with hydroxide, acetate, citrate, and oxalate anions. The computational framework is based on the Mixed-Solvent Electrolyte (MSE) framework, which has been previously used to establish a systematic treatment of binary and multicomponent systems containing REE sulfates and chlorides up to solid–liquid saturation at temperatures up to 300 °C. The model has been parametrized by performing a multi-property analysis of critically evaluated speciation and solubility data. For rare earth hydroxides, a comprehensive model has been developed for fourteen REEs (i.e., for yttrium and all lanthanides except promethium). The effect of the crystallinity of rare earth hydroxides on their solubility has been analyzed. Model parameters have been determined for two limiting cases, i.e., for crystalline and amorphous hydroxides, while recognizing that the hydroxides may span a range of degrees of crystallinity. For the organic ligands, the model has been established for neodymium with additional analysis for other selected REEs. The model accurately reproduces the effects of pH, temperature, and complexation with organic ligands on the behavior of rare earth elements in aqueous solutions. When coupled with previously developed models for inorganic rare earth salts, it provides a thermodynamic tool for the design and optimization of separation processes for the production and recycling of REEs and for predicting the properties of REEs in geological and biological settings.

Hydrothermal synthesis and ionic sensing properties of graphitic carbon nitride quantum dots

BackgroundThis work adopts an efficient method including thermal calcination, surface hydroxylation, and hydrothermal cutting to synthesize graphitic C3N4 quantum dots (CNQDs) for detecting metal ions in aqueous solutions. MethodsFunctionalized CNQDs, ranged from 2 to 6 nm in particle size, were of layered crystalline and contain a large amount of surface functionalities such as carbonyl, carboxylic, and amino groups. The CNQD suspension exhibited a maximal fluorescence intensity at 420 nm with high quantum yield of 13.6% under UV irradiation. Significant findingsThe CNQD suspension demonstrated superior sensitivity and selectivity toward iron ions with ppm-level detection limit in liquid phase. The Stern-Volmer analysis revealed that CNQD suspension was appropriate for the detection of Fe3+ and Fe2+ ions with LOD of 6.5 and 7.7 ppm, respectively. The fluorescence quenching mechanism of CNQD suspension mainly originates from a strong interaction between the ions and the surface functionalities followed by the photoinduced energy transfer effect, thus inducing the fluorescence extraction. Moreover, the CNQD suspension also offers a satisfactory biocompatibility toward 3T3 cell after 24 h. Accordingly, the robust design of CNQDs developed in this work paves the way for developing highly sensitive and selective probes for detecting target species in aqueous solutions.

Spectral characterization of fluorescein species in aqueous solution for laser-induced fluorescence thermometry

Spectral characterization of fluorescein species in aqueous solution for laser-induced fluorescence thermometry

One Molecule Suffices: Spectroscopy of Yariv Reagents

We have investigated the structure and spectra (NMR, UV/visible) of several Yariv reagents and models for these species, using both density functional theory (DFT) and approximate coupled-cluster methods (ADC(2)). We have also studied the formation of dimers and model trimers as a first step to understand the aggregation of these species in aqueous solution. One question that our calculations help resolve is the origin of two strong bands in the visible region of the spectrum: these are confirmed as resulting from enol-keto tautomerism, and are not a result of aggregation, which was a hypothesis that had been advanced previously. The UV/visible spectrum of the Yariv reagents can be explained entirely in terms of tautomerism within a single molecule – no dimers or clusters are involved.

Thermodynamic Data for Sn(IV) Species in Aqueous Solution: A Matter of Controversy and Error

Critically assessed data regarding Sn(IV) dioxides and hydroxy complexes have recently been challenged. Differences as large as nine orders of magnitude occur in certain of the published solubility products and other equilibrium constants, despite supposedly being derived from the same ‘reliable’ measurements. We show how these differing conclusions depend on the assignments of uncertainty in the respective experimental observations and that the divergence is due to error propagation in identifiable thermodynamic analyses. The use of Sn4+ as a ‘basis’/‘master’ species in thermodynamic modelling is deprecated. Automatic methods which enable the necessary calculations to be properly evaluated, as well as easily repeated, help uncover such mistakes. The results from the comprehensive NEA review are substantially confirmed.