Gibbs Free Energies Of Transfer Research Articles

Lipophilic EDTA-based ligands in different diluents for the extraction of rare earths: Preliminary results with Nd(III), Dy(III) and Pr(III) in chloride and nitrate media

A separation method for the recovery of neodymium(III) from two different media, chloride and nitrate, by implementing solvent extraction technique with a novel lipophilic diamide derivative of ethylenediamine tetraacetic acid (EDTA), namely 2,2’-N,N′-didecyl-dioxo-N,N′,N″,N″’-tetraazatetratriacontane-N″,N″’-diyl diacetic acid (H2E4C10), has been investigated. Initial screening results demonstrated acceptable solubility (ca. 15 mM) of the diamide in 1,3-diisopropylbenzene (DiPB) and in a 93:7 v:v n-dodecane:n-octanol mixture (DOm) as non-polar diluents. Further investigations aiming at determining operational parameters associated with the befitted extractant systems were conducted at pH ranging from 2 to 4 in chloride and nitrate media. A pH-dependent performance of the proposed systems revealed loading capacity peaking at pH = 3 with the respective values of 1.7 and 2.0 g L−1 in nitrate and chloride media. The extraction efficiency, the distribution coefficients, and the separation factor (E%,D and SF, respectively) were determined for an equimolar mixture of neodymium and two other potential competitive lanthanides, namely dysprosium and praseodymium. The best selectivity was observed in the chloride medium at pH = 4 yielding SFNd/Pr = 1.48 and SFNd/Dy = 2.03. Neodymium-to-extractant stoichiometry was evidenced in chloroform to be 1:1 H2E:Nd at pH = 2. Thermodynamic constants related to the considered extraction equilibrium have been determined by using the Van't Hoff relation and the slope analysis method. It appeared within the selected pH-range that the mechanism of the Nd3+ transfer was strongly influenced by the nature of the diluent. This was illustrated by the enthalpy-driven transfer when Nd3+ was extracted with the H2E-4C10-Dom system (aliphatic diluent) while the transfer became entropy-driven when the extraction was performed with the H2E-4C10-DiPB system (aromatic diluent). The complexation of Nd3+ involved mainly the participation of both the amide and carboxylic functional groups. The transfer of the cation to the organic phase might occur through the formation of the Nd(HE)A2 complex (where A is either a nitrate or a chloride anion), allowing for the lowest associated standard Gibbs free energy of transfer (−28 < ΔG° < −24 kJ mol−1) regardless of the aqueous feed.

Microscale cephalosporin ion-selective amperometric/voltammetric sensors based on a micropipette-supported liquid/liquid interface: Multiple purposes of transmembrane studies and real-time determinations

The permeability of cephalosporins through cell membranes is crucial for their efficacy against gram-negative bacteria. To address this, a microsoft biphasic sensor utilizing the interface between two immiscible electrolyte solutions (ITIES) has been introduced for studying the ion transfer of cefotiam (CTM), ceftazidime (CAZ) and cefepime (CPM). The typical voltammograms of cephalosporin ion transfer can be further used to determine the formal ion transfer potentials (∆owφA′), ion transfer Gibbs free energies (∆owGA′), effective hydrophilicity (logPi), geometry of micro-ITIES, diffusion coefficient (Dw) and ion transfer rate constant (k0). In addition, the partitioning of CTM+, CAZ+, and CPM+ in two phases at different pH values was revealed by the corresponding ion partition diagrams (IPDs). The IPDs can further elucidate the mechanism of cephalosporin ion transfer across the ITIES at different pH values. Finally, the determination of CTM+, CAZ+ and CPM+ was achieved via real-time chronoamperometry. An excellent linear range for cephalosporin ions with a satisfactory limit of detection was obtained. The findings show the superb selectivity and anti-interferent ability of micro-ITIES sensors toward cephalosporins. The constructed micro-ITIES sensors for cephalosporin could contribute to medicinal design, single microorganism metabolism analysis, clinical diagnosis, and food safety inspection.

Investigation of micellization and thermodynamic properties of cationic gemini surfactant (12-2-O-2-12) in the presence of organic solvents

The micellization behaviour and thermodynamic properties of synthesized cationic gemini surfactant (12-2-O-12-12), N,N′-didodecyl-N,N,N′,N′-tetramethyl-N,N′-(oxybis(ethane-2,1-diyl))-diammonium dibromide were studied in the presence of organic solvents for four different temperatures (25, 30, 35 and 40 °C). Aqueous solutions of 10 % and 20 % methanol (MeOH), ethanol (EtOH), isopropanol (IPOH) and dimethyl sulfoxide (DMSO) were used as solvents. The critical micelle concentration (CMC) of cationic gemini surfactant and the degree of counterion dissociation (α) were determined by the conductometric method. Using the CMC and α values for each of the four temperatures, the values of the standard Gibbs free energy (ΔGmo), Gibbs free energy of transfer (ΔGm,transo), enthalpy (ΔHmo), and entropy (ΔSmo) of micellization were calculated. It was observed that the CMC and α values increased with increasing solvent percentage and temperature. It was found that in all cases, the standard Gibbs free energy and enthalpy values were negative while both the micellization entropy and the standard Gibbs free energy of transfer are positive. Negative Gibbs free energy values indicated that micellization was a spontaneous situation, while positive entropy values indicated the existence of a disordered situation. The positive ΔGm,transo values show that the presence of solvents makes the environment unfavorable for micelle formation.

Cheap and effective potentiometric PVC sensor for the determination of imidazolium based ionic liquids in aqueous and aqua-organic media

Owing to the extensive research on imidazolium based ionic liquids; the present study aims to design a potentiometric sensor for alkyl methylimidazolium ion. For this, poly(vinyl chloride) PVC membrane based on the neutral ion-pair complexes of cetylpyridinium chloride and sodium dodecyl sulfate (CPy+DS−) has been developed. The synthesized ion selective electrode (ISEs) have been found to show linear response with near-Nernstian slope for CnMeImCl (C10MeImCl, C12MeImCl and C14MeImCl). The proposed ISEs show quick response (5–6 s) and provide wide pH range for working. The influence of various ions on the performance of ion-selective electrode is investigated in terms of potentiometric selectivity coefficients, which were determined by separate solution method. The performance of synthesized ISE in examining the critical micellar concentration (cmc) of CnMeImCl in aqueous, aqua-organic media and in the presence of amino acids (glycine, L-glutamic acid and L-phenylalanine) has been found to be satisfactory and confirmed through conductivity and fluorescence measurements. This emphasizes its worth for in-situ analysis of alkyl methylimidazolium ions, during an organic reaction, and hence possible reaction mechanism evaluation. Different thermodynamic parameters such as Standard Gibbs energies of micellization (ΔGm∘), degree of counterion dissociation (α), amphiphile tail transfer Gibbs free energy (ΔGm,trans∘) have been evaluated. Further, the analytical application of synthesized electrode as end point indicator in the potentiometric titration of C14MeImCl with SDS has also been explored, which compared well with improved two-phase titration method. The current study is novel as it involves the use of a cheaper material (CPyCl) as ionophore and that the same electrode can be used for different chain alkyl methylimidazolium ions simply by changing the internal reference solutions.

Thermodynamic studies on the formation of ion-pair cobalt complexes in acetone–water mixtures

Dicarboxylic acids are stronoger acids than moncraboxylic acids and more soluble in water due to the presence of two carboxylic (–COOH) groups which are industrially important in producing polyester, polyamides, and polyols and as a pioneer to pharmaceutical additives. Succinic acid is one of the most prosperous chemicals that can be generated from renewable resources which can be used in the industries of antiseptics, cosmetics, sutures, drugs, solvents, detergents, herbicides, fungicides, synthetic resins, and inks. The ion–pair formation is very important in diferent applications, used widely for inorganic analysis by liquid chromatography and used for the heavy metal removal from waste water, so studing the ion-pair association constant (KA) formed between chloropentamminecobalt(III) cation [CpX2+] and a different ligands of dicarboxylate anions (AC2-), have been determined by EMF technique in different compositions of acetone aqueous media (0–44.20 wt% acetone) for succinic acid and for the other dicarboxylic acids (Maleic, Malonic and Malic) in the same solvent composition (40 wt% acetone) with in temperature range (30 – 60 °C). The thermodynamic association properties (ΔGA°, ΔHA° and ΔSA°) have been estimated and discussed. Extra thermodynamic correlations like ΔHA°- ΔSA° and ΔGA°- ΔGI(orII)° (where I and II are mentioned for the first and second dissociation constant of the dicarboxylic acids) in different compositions of acetone aqueous media for succinic acid and in fixed solvent composition for the other dicarboxylic acids were examined in order to give more information about the behavior of solvent molecules and its effect on formation of the ion-pair molecules. In addition, The Gibbs free energy of transfer for the association process ΔGA°(t) from water to acetone mixed solvents were calculated for succinic acid in order to indicate the spontaneous nature and the stabilization of the ion-pair by increasing the acetone weight percent in the mixed acetone – aqueous media. The linear correlation between pKD values and the relative permittivity of acetone aqueous medium is in accordance to Born’s equation.

Analyzing of L-tryptophan thermodynamics and its solubility in aqueous acetonitrile blends at diverse temperatures

This paper delves into an investigation of the solubility characteristics of L-tryptophan within binary solvent systems containing aqueous acetonitrile. The primary emphasis of the study revolves around assessments based on mole fractions. The study utilizes these solubility values to assess thermodynamic constraints, including solution entropies and solution transfer free energetics. The calculated thermodynamic energies are correlated with interaction parameters, including Gibbs free energies and entropies, pertaining to the transfer of L-tryptophanfrom water to binary solvent blends of acetonitrile and water. Mathematical expressions are utilized to determine the transfer Gibbs free energies for chemical interactions, and the consequent entropies are clarified within the framework of solvent-solvent interactions. To expound upon the stability of L-tryptophan within the water-acetonitrile mixed system, we investigate the energetic aspects related to the transfer of chemicals Gibbs free energies. Additionally, standard temperature (298.15 K) is employed to calculate various related physicochemical parameters of solute/solvent.

Molecular modelling of fullerene C60 functionalized by nitric oxide for use in biological environment

The unique potential of fullerene C60 for various biological applications has ignited significant interest. However, its inherent non-polarity poses a critical challenge for its effective integration within biological systems. This study delves into the intricate physicochemical characteristics of the innovative [C60 + NO] complex using density functional theory and time-dependent density functional theory. The computational analyses encompass molecular charge, surface electrostatic potential, and dipole moment evaluations. Impressively, the dipole moment of the [C60 + NO] complex significantly increases to 12.92 D. Meticulous surface analysis reveals a subtle interplay between molecular structures, indicating weak interactions. The analysis of the absorption spectrum unveils a noteworthy red-shift of 200 nm subsequent to complex formation. To elucidate the electron transfer mechanisms, we explore photo-induced electron transfer through CAM-B3LYP. This exploration elucidates intricate pathways governing electron transfer, with complementary insights gleaned from Marcus theory's outputs, especially the Gibbs free energy of electron transfer. Changes in the physicochemical properties of approaching C60 and NO molecules reveal interesting results compared to separate molecules. These findings resonate profoundly in the context of potential biological and pharmaceutical utilization. With implications for the biomedical area, the outcomes linked to the [C60 + NO] complex kindle optimism for pioneering biomedical applications.

Design and application of supramolecular based solid-contact ion-selective electrode for selective green determination of tenofovir disoproxil fumarate

This work describes the fabrication of solid-contact potentiometric sensor to determine the antiviral drug; tenofovir disoproxil fumarate. Screen-printed carbon electrodes have been selected as being a disposable substrate material. Ion sensing membrane is based on Polyvinyl chloride (PVC) polymer that was impregnated with calix [6] arene as being an ionophore for facilitating transferring the drug of interest from the sample phase into the membrane phase through decreasing Gibbs free energy of transfer. We applied a graphene nanocomposite interlayer between the carbon substrate and the polymeric membrane for overcoming potential drift, which is commonly encountered in solid-contact potentiometric sensors. As a result, the graphene nanocomposite layer enhanced the sensor performance and stabilized the potential signal as compared to the control sensor. The sensor performance characteristics were studied according to International Union of Pure and Applied Chemistry (IUPAC) recommendations, and linear range has been 0.01 M - 10 μM with limit of detection (LOD) 7.3 μM. We utilized the sensor for inline determination of the release of tenofovir disoproxil fumarate from its tablet pharmaceutical formulation without any separation or sample pre-treatment steps. In an attempt to be eco-friendly through evaluating the suggested method regarding its greenness, the method has been found to be excellent green according to the eco scale method.

Study of the molecular interaction of a phosphonium-based ionic liquid within myo-inositol and non-steroidal anti-inflammatory drugs.

Ionic liquids (ILs) can be used as carriers and solubilizers as well as for increasing the effectiveness of drugs. In the present investigation, the micellar properties of phosphonium-based ionic liquids (PILs) such as trihexyltetradecylphosphonium bis(2,4,4-trimethylpentyl)phosphinate ([P666(14)][THPP]) and the effect of carbocyclic sugar-based myo-inositol (MI) and non-steroidal anti-inflammatory drugs (NSAIDs), i.e. ibuprofen (IBU) or aspirin (ASP), on the PIL micellar system were studied using surface tension, conductivity, colorimetry, viscometry, FTIR, and dynamic light scattering (DLS) at a temperature of 299 ± 0.5 K. The critical micelle concentrations (CMCs), particle size, zeta potential, and various interfacial parameters were also included i.e., efficiency of adsorption (pC20), surface tension at CMC (γCMC), minimum surface area per molecule (Amin), surface pressure at CMC (πCMC), maximum surface excess concentration (Γmax), and various thermodynamic parameters, such as standard Gibbs free energy of adsorption , standard Gibbs free energy of micellization per alkyl tail , standard Gibbs free energy of the air-water interface (ΔG(s)min), standard Gibbs free energy of transfer , and standard Gibbs free energy of micellization . The adsorption and micellization characteristics became more spontaneous, as shown by the more negative values of and . Viscosity-based rheological properties were calculated for various PIL + MI and PIL + MI + NSAID systems. According to the DLS data, the PIL (Z = 316.4 nm) micellar system generates substantially bigger micelles in an aqueous solution of MI + ASP (Z = 801.7 nm) than in MI + IBU (Z = 674.7 nm). FTIR spectroscopy revealed the interactions of PIL with MI + ASP and MI + IBU, where it was observed that MI + IBU shows good agreement with the PIL system compared to MI + ASP. The current research will have effects on pharmaceutical sciences, molecular biology, and drug delivery.

Probing coumarin solubility and solvation energetics in diverse aqueous–organic solutions across a temperature range: A debut exploration

In this research, an investigation was conducted to explore the solubility of coumarin in both aqueous solutions and binary mixtures, specifically in pure and aqueous ethylene glycol (EG), aqueous 2-methoxyethanol (ME), and aqueous 1,2-dimethoxyethane (DME). Solubility experiments were conducted first time using UV–Vis spectroscopy at a temperature range of 288.15–313.15 K at a pressure of 0.1 MPa for the current solute solvent systems. A digital thermostat was used to maintain the precise temperature. The findings indicated that coumarin exhibits its highest solubility in pure DME (3.0824 mol·kg−1) and its lowest solubility in pure EG (0.0169 mol·kg−1) across all temperatures. Various solvation parameters were calculated to enable the determination of solvation-related thermodynamic properties. The experimental results were used to evaluate various thermodynamic parameters including solution Gibbs free energies, transfer Gibbs free energies associated with cavity and dipole–dipole interactions, enthalpy of transfer, and non-covalent transfer energies. The focus of this research was on to provide insights into the thermodynamics of coumarin-like organic molecules when dissolved in solutions. The study aimed to contribute valuable information regarding the stability of coumarin, particularly in relation to non-covalent interactions. These insights have potential to influence the manufacturing and purification processes, thereby expanding its potential applications across various industries.

Full theoretical protocol for the design of metal-free organic electron donor-spacer-acceptor systems.

A user-friendly (time-dependent) density functional theory based algorithm is proposed to design new donor-spacer-acceptor systems for electron transfer reactions. This algorithm is focused on metal-free organic compounds, most of which contain aromatic or alkene moieties. The oxidation and reduction potentials are calculated, together with the excited-state energy difference including the zero-point energy and the structural properties required to calculate an electron transfer Gibbs free energy change. The proposed algorithm has been tested on well-known systems, while two new compounds are suggested for photoinduced intramolecular electron transfer reactions using this scheme. The methodology here presented is intended to be a tool for synthetic physical-chemists, allowing them to evaluate the properties of hypothetical systems before the synthesis, enabling the study of limitless combinations of donor-spacer-acceptor arrangements.

An in-silico study to gain a comprehensive understanding of the effects of glucosylation on quercetin properties

In order to gain a molecular understanding of why quercetin characteristics are altered by glucosylation, DFT calculations and MD simulations were utilized. According to DFT findings, glucosylation of quercetin altered its structural stability, molecular polarity, molecular polarizability, and Gibbs free energy of transfer, which gives a molecular explanation for the observed alterations in the aqueous solubility and lipophilicity of derivatives. The outcomes of MD simulations also demonstrated how the various hydroxyl groups of quercetin interact with solvent molecules and how glucosylation can have an impact on that. Additionally, it was shown that glucosylation often increased the number of hydrogen bonds and the nonbonded interaction energies between the molecules of the solvent and the solute. The solubility behavior of glucosylated derivatives in water and alcoholic solvents can be reasonably interpreted molecularly using these results, which could suggest approaches for improving the features of these kinds of bioactive compounds.

Cluster-Continuum Model as a Sanity Check of Sodium Ions' Gibbs Free Energies of Transfer.

An approach to estimate the uncertainty of the calculated through the monomer cycle cluster-continuum model Gibbs free energy of transfer has been developed and suggested to be used as a quantitative measure of the reliability of the predictions. A set of experimental Na+ free energies of transfer from water to 18 solvents (ΔGtr(Na+, W → S)) has been assessed. For all solvents, we find Na+(S)n clusters to be thermodynamically unstable if n > 5. For 1,2-dichloroethane (1,2-DCIE), we have resolved considerable (ca. 10 kcal mol-1) discrepancies between available experimental ΔGtr(Na+, W → S). For 1,1-DCIE, we reject the only available experimental value and recommend our own estimate instead. We strongly propose experimental revisiting of ΔGtr(Na+, W → S) for ethylene glycol and hexamethylphosphoramide. The statistical analysis performed on a set of predicted and recommended experimental ΔGtr(Na+, W → S) values, in this work, results in the mean unsigned and signed deviations of 3.4 and -1.3 kcal mol-1, respectively. The squared Pearson correlation coefficient of 0.91 encourages the extension of the utilized theoretical approach to other available experimental data on ion solvation.

Hot-melt extrusion promotes dissolution, extends “spring-parachute” process and inhibits crystallization in supersaturating microparticle systems

Despite the potential advantages of amorphism-induced supersaturation, the merit of new amorphization formation methods on the properties of the amorphous drug including the stability of the amorphous state, dissolution/solubility, supersaturation, and “spring-parachute” process is still poorly understood, particularly for certain amorphous supersaturating drug delivery systems (aSDDS). The present work aimed to explore the detailed merit of current attractive amorphization manufacturing methods (i. g., hot-melt extrusion (HME) technique) on the property improvement of aSDDS in form of amorphous solid dispersion microparticles by employing a model BCS II drug nitrendipine and a polyvinylpyrrolidone-based model polymer copovidone. Many aSDDS systems were developed by various methods, and their physicochemical properties were characterized by SEM, PXRD and DSC. HME-triggered amorphization induced superior supersaturation by the observation of the highest dissolution and solubility. HME induced the optimal supersaturation duration by the observed greatest extension of “spring-parachute” process (e. g., maximum AUCspring-parachute). HME technique is comparable with other techniques for the stabilization of amorphous state during storage. All aSDDS systems by HME and other methods showed improved long-term stability of the amorphous state in comparison to the pure amorphous drug. Fourier transformation infrared spectroscopy, Noyes-Whitney equation, nucleation theory and Gibbs free energy of transfer (ΔGto) were used to analyze the underlying mechanisms. Molecular mechanism studies indicated that HME caused a stronger crystallization inhibition effect in the aSDDS systems than other methods, but molecular interaction is not a dominant mechanism for property enhancement caused by HME. For the mechanism associated with the polymer itself (PVPVA64), it could inhibit the drug recrystallization, solubilize the drug spontaneously and cause the improved molecular interactions in all aSDDS systems. This study provided a deep insight into detailed advantage of HME-triggered supersaturation/amorphization and facilitated the applications of the technique both in the field of particuology and in pharmaceutical industry.

Solvation of dibenzo-18-crown-6 ether in water-aprotic solvents

The Gibbs free energies of transfer of dibenzo-18-crown-6 ether from dimethyl sulfoxide and N,N-dimethylformamide to their mixtures with water (ΔtrG0(DB18C6)solv→χW) were determined by the interphase distribution method. The enthalpies of dissolution of DB18C6 were determined by the calorimetric method at 25.00 ± 0.01 °C. The analysis of the influence of solvent composition and properties on the thermodynamic characteristics of DB18C6 solvation was carried out. It was found that a change in the solvent composition in both cases does not lead to significant changes in the crown ether solvation state. A compensation effect in enthalpy and entropy contributions to ΔtrG0(DB18C6) was observed. It has been shown that the priority contribution to the change in the thermodynamic characteristics of DB18C6 solvation is made by the resolvation of the crown ring oxygen atoms. The resolvation of DB18C6 occurs at χW > 0.6 mol fr. Proper data are compared with data reported in the literature.

Disclosing the distribution regularities for chiral recognition exemplified by R-and RS- of new antifungal: Impact of pH and temperature

The overall investigation of the distribution behavior for the enantiomer (R-98) and racemic (RS-186) antifungal compounds was carried out to the aim of disclosing the possibility of chiral differentiation. To this end, the study on the thermodynamics of the distribution coefficients in the model systems 1-octanol/water and n-hexane/water was performed. The impact of pH on the transferring of the compounds was revealed by using buffer solutions at pH 2.0 and pH 7.4 as an aqueous phase. The transferring mechanisms for different distribution systems were disclosed based on the complex analysis of the enthalpy and entropy contributions to the Gibbs energy and involved in chiral discrimination. A separation factor or enantioselectivity, as well as the differences between the transfer Gibbs free energy, enthalpy and entropy (excess thermodynamic functions) were determined and discussed. The maximal value of the separation factor in the 1-octanol/buffer pH 7.4 system was shown. The impact of the hydrogen binding potential of the substances on the enantioselectivity was detected.

Voltammetric Study of Lomefloxacin Transfer at the Interface between Two Immiscible Electrolyte Solutions: Ionic Partition, Photodegradation, and Sensing Applications

AbstractThe transfer of ionizable lomefloxacin (LOM) across a polarized interface between two immiscible electrolyte solutions (ITIES) was studied using cyclic and differential pulse voltammetry (DPV). The pH values of water (ionic strength=0.02 M) interfacing with the 1,2‐dichloroethane phase were varied to investigate the transfer behavior of differently charged LOM species, including protonated, neutral, and zwitterionic forms of LOM, namely HLOM+, LOM0, and H+LOM−. An ionic partition diagram for LOM was drawn with DPV response at various pH values, and the distinctive features of LOM were compared to those of fluoroquinolone antibiotics, which have similar pKa values. Physical and thermodynamic properties, including the formal transfer potential, lipophilicity, and Gibbs free energy of transfer of LOM were also evaluated. Furthermore, the photodegradation properties of differently charged LOM species and ophthalmic LOM drop samples (pH 5.0) were investigated after exposure to a UV (λ=365 nm) source. Quantitative analysis of HLOM+ concentrations in buffer and diluted commercial eye drop solutions containing LOM was finally demonstrated using differential pulse stripping voltammetric responses at pH 3.0 and 5.0 involving the transfer of HLOM+ at a polarized microhole‐water/polyvinylchloride‐2‐nitropheyloctylether gel interface.

Investigation of ion pairs in electrochemical ferrocene methanol –Ferrocenium methanol system in presence of supporting electrolyte

Density functional theory (DFT) has been applied to consider ion pair formation in ferrocenium methanol and ferrocene methanol aqueous solutions in the presence of a supporting electrolyte. Based on DFT calculation, the free energy of all species is calculated to evaluation the equilibrium constant. Henry constant of electrochemical ion pair species has been calculated based on transfer Gibbs free energy and combination free energy. DFT calculation in water solvent has been extended to calculate electrode potential as a function of supporting electrolyte. Polarizable continuum model (PCM) is applied for calculating HOMO and LUMO orbitals for ferrocenium methanol - chloride ion pair. DFT-PCM calculation has been done to get chemical structure of ion pair and all electrochemical species. DFT-PCM calculation shows that ion pair reaction between ferrocenium methanol and Cl− ion is an exothermic process. Theoretical DFT calculation results regarding chemical bond length and standard electrical potential of ferrocenium methanol to ferrocene methanol versus standard hydrogen electrode are agreement to the experimental result.

An Image Analysis Pipeline for Quantifying the Features of Fluorescently-Labeled Biomolecular Condensates in Cells.

Biomolecular condensates are cellular organelles formed through liquid-liquid phase separation (LLPS) that play critical roles in cellular functions including signaling, transcription, translation, and stress response. Importantly, condensate misregulation is associated with human diseases, including neurodegeneration and cancer among others. When condensate-forming biomolecules are fluorescently-labeled and examined with fluorescence microscopy they appear as illuminated foci, or puncta, in cells. Puncta features such as number, volume, shape, location, and concentration of biomolecular species within them are influenced by the thermodynamics of biomolecular interactions that underlie LLPS. Quantification of puncta features enables evaluation of the thermodynamic driving force for LLPS and facilitates quantitative comparisons of puncta formed under different cellular conditions or by different biomolecules. Our work on nucleoporin 98 (NUP98) fusion oncoproteins (FOs) associated with pediatric leukemia inspired us to develop an objective and reliable computational approach for such analyses. The NUP98-HOXA9 FO forms hundreds of punctate transcriptional condensates in cells, leading to hematopoietic cell transformation and leukemogenesis. To quantify the features of these puncta and derive the associated thermodynamic parameters, we developed a live-cell fluorescence microscopy image processing pipeline based on existing methodologies and open-source tools. The pipeline quantifies the numbers and volumes of puncta and fluorescence intensities of the fluorescently-labeled biomolecule(s) within them and generates reports of their features for hundreds of cells. Using a standard curve of fluorescence intensity versus protein concentration, the pipeline determines the apparent molar concentration of fluorescently-labeled biomolecules within and outside of puncta and calculates the partition coefficient (Kp) and Gibbs free energy of transfer (ΔGTr), which quantify the favorability of a labeled biomolecule partitioning into puncta. In addition, we provide a library of R functions for statistical analysis of the extracted measurements for certain experimental designs. The source code, analysis notebooks, and test data for the Punctatools pipeline are available on GitHub: https://github.com/stjude/punctatools. Here, we provide a protocol for applying our Punctatools pipeline to extract puncta features from fluorescence microscopy images of cells.

Defined Ion-Transfer Voltammetry of a Single Microdroplet at a Polarized Liquid/Liquid Interface.

A strategy for the fast analysis of ion transfer/facilitated ion transfer toward a tiny (femtoliter) water-in-oil droplet has been established. This scenario is embodied by the fusion of a w/o microdroplet at the micro liquid/liquid (L/L) interface, with the use of Fourier transform fast-scan cyclic voltammetry (FT-FSCV) to express the apparent half-wave potentials of anions or cations encapsulated inside the w/o microdroplet. First, the half-wave potential is in strict accordance with the transfer Gibbs free energy of either cations or anions. Second, the half-wave potential has been found to be positively proportional to the logarithmic concentration of ions, shedding thermodynamic insight into ion transfer. Third, as an instance of multivalent biopolymers, the transfer of protamine inside the single w/o microdroplet has been investigated. Obvious discrepancies in the behaviors of the fusion impacts at different pH, as well as in the absence and presence of the cationic surfactant DNNS-, are revealed. The internal mechanism of protamine transfer has been thoroughly investigated. This work proposes a strategy to sensitively and quickly determine the transfer Gibbs energy and the concentration of ions encapsulated in a single microdroplet, and it provides the possibility of analyzing the interfacial transfer properties of trace biomacromolecules inside an aqueous micro- or nanoscale droplet.