Interaction Of Ions Research Articles

Metal‐chelating antioxidant peptides: Biosensor screening methods as alternatives to the ferrozine assay

AbstractPreventing metal‐catalyzed lipid oxidation in food products, which decreases nutritional value and sensory quality, is crucial in the food industry. This is typically achieved through the use of metal‐chelating molecules. While the ferrozine assay is widely used to screen protein hydrolysates for metal chelating activity, it has proven difficult to use with pure peptides. This study evaluates the potential of surface plasmon resonance (SPR) and electrically switchable nanolever technology (switchSENSE®) as alternative screening methods. Unfortunately, solubility issues and large standard deviations precluded a direct correlation between the ferrozine assay and these biosensor techniques. Both techniques, however, were able to quantitatively distinguish between two peptides with very similar sequences despite the absence of a correlation between dissociation constants determined by SPR and switchSENSE®. This study highlights the potential of SPR and switchSENSE® for screening the metal chelating activity of pure peptides, advancing the understanding of peptide‐metal ion interactions.

Energy storage application of plasticized biopolymer blend electrolyte doped with ammonium nitrate as H+ provider

Recently, proton-conducting electrolytes for energy storage purposes attracted the focus of many research groups as possible alternatives for Li-based energy storage applications. Natural polymers offer a promising solution to counter the environmental impact of synthetic polymers. In this work proton conducting CS:POZ based natural polymer electrolytes were plasticized with glycerol (GL) to improve the ion conductivity and increase the free ion percentage. The films of CS:POZ:NH4NO3 electrolyte were prepared using the casting technique. The plasticizers were changed from 9 to 36 wt%. The FTIR method revealed ion interaction among polymer, salt, and plasticizer. The deconvolution of FTIR band associated with NO3 anion was used to calculate the ion transport parameters (ITPs). It was found that the free ion contour area was enhanced by increasing plasticizer concentration. The EIS plot fitted with equivalent circuit elements was used to determine the DC conductivity and ITPs. The dominancy of ion species was examined using TNM measurement. The safety region for energy storage device (ESD) application was found from the LSV examination. The activated carbon was used to manufacture the electrodes for ESD application. The cyclic voltammetry (CV) investigation found that the capacitances of the ESD influenced by scan rates.

A comprehensive review of protein-centric predictors for biomolecular interactions: from proteins to nucleic acids and beyond.

Proteins interact with diverse ligands to perform a large number of biological functions, such as gene expression and signal transduction. Accurate identification of these protein-ligand interactions is crucial to the understanding of molecular mechanisms and the development of new drugs. However, traditional biological experiments are time-consuming and expensive. With the development of high-throughput technologies, an increasing amount of protein data is available. In the past decades, many computational methods have been developed to predict protein-ligand interactions. Here, we review a comprehensive set of over 160 protein-ligand interaction predictors, which cover protein-protein, protein-nucleic acid, protein-peptide and protein-other ligands (nucleotide, heme, ion) interactions. We have carried out a comprehensive analysis of the above four types of predictors from several significant perspectives, including their inputs, feature profiles, models, availability, etc. The current methods primarily rely on protein sequences, especially utilizing evolutionary information. The significant improvement in predictions is attributed to deep learning methods. Additionally, sequence-based pretrained models and structure-based approaches are emerging as new trends.

Nucleophilicity mediated interactions of ions with sensor: An anion induced BODIPY based chemodosimeter for sensing of CO2 gas

A BODIPY based chemodosimeter was designed and synthesized for detection of CO2 gas in presence of F−/CN− ion. The changes were observed in the absorption spectra of the probe and corresponding colour changes were clearly distinguished by naked eye. The mechanism of sensing was studied by NMR titration which reveals that unlike previous reports our probe can detect as well as trap CO2 through adduct formation. The sensing of CO2 was also extended to solid state through immobilizing the probe into hydrogel matrix as well as onto silica. Both hydrogel composite and silica loaded with the probe exhibit colour changes upon exposure to CO2. Also, the practical application of the probe was demonstrated through detection and estimation of dissolved CO2 in carbonated beverages. Moreover, the probe can detect F− and CN− through two different mechanisms governed by the nucleophilicity of the anion. The type of interaction of the probe with F− and CN− were elucidated with absorption and NMR study. Both the F− and CN− ions induced quenching of emission of the probe owing to activation of PET (Photo-induced Electron Transfer). The anion induced change in fluorescence intensity of the probe was also demonstrated with theoretical study. Moreover, the practical applicability of the probe for CN− sensing was established through sensing of CN− in 100% aqueous solution.

Substantially Accelerated Response and Recovery in Pd-Decorated WO3 Nanorods Gasochromic Hydrogen Sensor.

The development of hydrogen (H2) gas sensors is essential for the safe and efficient adoption of H2 gas as a clean, renewable energy source in the challenges against climate change, given its flammability and associated safety risks. Among various H2 sensors, gasochromic sensors have attracted great interest due to their highly intuitive and low power operation, but slow kinetics, especially slow recovery rate limited its further practical application. This study introduces Pd-decorated amorphous WO3 nanorods (Pd-WO3 NRs) as an innovative gasochromic H2 sensor, demonstrating rapid and highly reversible color changes for H2 detection. In specific, the amorphous nanostructure exhibits notable porosity, enabling rapid detection and recovery by facilitating effective H2 gas interaction and efficient diffusion of hydrogen ions (H+) dissociated from the Pd nanoparticles (Pd NPs). The optimized Pd-WO3 NRs sensor achieves an impressive response time of 14s and a recovery time of 1s to 5% H2. The impressively fast recovery time of 1s is observed under a wide range of H2 concentrations (0.2-5%), making this study a fundamental solution to the challenged slow recovery of gasochromic H2 sensors.

Mutations influence the conformational dynamics of the GDP/KRAS complex

Mutations near allosteric sites can have a significant impact on the function of KRAS. Three specific mutations, K104Q, G12D/K104Q, and G12D/G75A, which are located near allosteric positions, were selected to investigate the molecular mechanisms behind mutation-induced influences on the activity of KRAS. Gaussian accelerated molecular dynamics (GaMD) simulations followed by the principal component analysis (PCA) were performed to improve the sampling of conformational states. The results revealed that these mutations significantly alter the structural flexibility, correlated motions, and dynamic behavior of the switch regions that are essential for KRAS binding to effectors or regulators. Furthermore, the mutations have a significant impact on the hydrogen bonding interactions between GDP and the switch regions, as well as on the electrostatic interactions of magnesium ions (Mg2+) with these regions. Our results verified that these mutations strongly influence the binding of KRAS to its effectors or regulators and allosterically regulate the activity. We believe that this work can provide valuable theoretical insights into a deeper understanding of KRAS function. Communicated by Ramaswamy H. Sarma

Solvothermal self-assembly of seven lanthanide(III) coordination polymers using diphenic acid and 1,10-phenanthroline as co-ligands: Efficient detection of picric acid and Cu2+ ions in aqueous medium by europium based coordination polymer

Lanthanide based coordination polymers (Ln-CPs) act as efficient chemo-sensors on interaction with the target analyte and show a detectable variation in their optical properties. This work demonstrates interaction of metal ions and nitroaromatic compounds with Eu based CP resulting in quenching of luminescence emission intensity. Approaching towards this aim, seven iso-structural lanthanide coordination polymers having the formulae, [Ln(diphen)1.5(1,10-phen)(H2O)] where Ln = Sm (1), Gd (3), Dy (5), {[Ln(diphen)1.5(1,10-phen)(H2O)]·OH} Ln = Eu (2), Er (7) and {[Ln(diphen)1.5(1,10-phen)(H2O)]·CH3CN·H2O} Ln = Gd (4), Ho (6) (diphen = diphenic acid, 1,10-phen = 1,10 Phenanthroline), were assembled solvothermally by using diphenic acid and 1,10-Phenanthroline as ligands. These lanthanide coordination polymers were characterized by Single-crystal X-ray diffraction, FTIR, Powder X-ray diffraction, Thermogravimetric analysis, UV–visible spectroscopy and Photoluminescence. The CPs 1–7 possess one-dimensional (1D) infinite chain-like structures which crystallize in the monoclinic C2/c space group. The photoluminescence properties of CP 2 exhibit its sensing ability to detect some toxic nitroaromatic compounds and d-block metal ions. However, CP 2 shows highly sensitive behavior for the recognition of Cu2+ and picric acid as indicated by efficient luminescence quenching with the low limit of detection. Other metal ions (viz., Cr3+, Cu2+, Co2+, Zn2+, Mn2+, Ni2+, Cd2+, and Hg2+), and nitro compounds (viz., PA, m-DNB, p-NP, p-NA and NB) were also screened for sensing potential of CP 2.

Fe-induced modifications in the magnetic and dielectric response of EuTiO3: Unraveling the linkage to oxygen vacancies

EuTi1−xFexO3 (x = 0.0–0.5) is studied to analyze the effect of Fe substitution on structural, dielectric and magnetic properties. We found that Fe substitution in place of Ti increases the barrier for charge carrier hopping therefore, suppresses the electrical conduction in the material. It has also been observed that characteristic G-type antiferromagnetic ordering of pure EuTiO3 can be significantly modified with Fe doping. Interestingly, formation of oxygen vacancies due to Fe substitution allows next nearest neighbor Eu ion interaction and generates ferromagnetic response in the magnetic hysteresis loops. Magnetic phase transition temperature also shifts to the higher temperature side with the increase in Fe concentration till x = 0.3 which implies strengthening of magnetic interaction. Schematic models based on the crystal and electronic structure are presented to explain the observed dielectric and magnetic response and it is concluded that both features can be tuned by the Fe substitution.

Isolation and identification of a high-efficiency hexavalent uranium adsorption strain and preliminary study of the influencing factors and adsorption mechanism.

In this study, a bacterial strain Chryseobacterium bernardetii WK-3 was isolated from the rhizosphere soil of a uranium tailings in Southern China. It can efficiently adsorb hexavalent uranium with an adsorption ratio of 92.3%. The influence of different environmental conditions on the adsorption ratio of Chryseobacterium bernardetii strain WK-3 was investigated, and the adsorption mechanism was preliminarily discussed by scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDS). The results showed that the optimal adsorption conditions for U(VI) by Chryseobacterium bernardetii strain WK-3 were pH = 5, temperature 30 ℃, NaCl concentration 1%, and inoculation volume 10%. When the initial concentration of U was 50 ~ 150mg/L, the adsorption capacity of Chryseobacterium bernardetii strain WK-3 to U(VI) reached the maximum and maintained the equilibrium at 44h. SEM-EDS results showed that phosphorus in cells participates in the interaction of uranyl ions, which may indicate that phosphate was produced during cell metabolism and was further combined to form U(VI)-phosphate minerals. In summary, Chryseobacterium bernardetii strain WK-3 would be a promising alternative for environmental uranium contamination remediation.

Lanthanide transport in angstrom-scale MoS2-based two-dimensional channels.

Rare earth elements (REEs), critical to modern industry, are difficult to separate and purify, given their similar physicochemical properties originating from the lanthanide contraction. Here, we systematically study the transport of lanthanide ions (Ln3+) in artificially confined angstrom-scale two-dimensional channels using MoS2-based building blocks in an aqueous environment. The results show that the uptake and permeability of Ln3+ assume a well-defined volcano shape peaked at Sm3+. This transport behavior is rooted from the tradeoff between the barrier for dehydration and the strength of interactions of lanthanide ions in the confinement channels, reminiscent of the Sabatier principle. Molecular dynamics simulations reveal that Sm3+, with moderate hydration free energy and intermediate affinity for channel interaction, exhibit the smallest dehydration degree, consequently resulting in the highest permeability. Our work not only highlights the distinct mass transport properties under extreme confinement but also demonstrates the potential of dialing confinement dimension and chemistry for greener REEs separation.

The effect of social media marketing on voting intention; an application of multidimensional panel data

PurposeThis study examines the effect of social media marketing on voting intention applying a combination of fuzzy logic methodology and a multidimensional panel data model.Design/methodology/approachThe study adopts a multidimensional panel data method that includes several fixed effects. The dependent variable is a multifaceted construct that measures the participants’ intention to vote. The independent variables are electronic word of mouth (eWOM), customisation (CUS), entertainment (ENT), interaction (INT), trendiness (TRD), candidate’s perceived image (CPI), religious beliefs (RB), gender and age. The grouping variables that signify fixed effects are employment status, level of education, mostly used social media and religion. First, the significance of said fixed effects was tested through an ANOVA process. Then, the main model was estimated, including the significant grouping variables as fixed effects.FindingsEmployment status and level of education were significant fixed effects. Also, eWOM, ENT, INT, CPI, RB and gender significantly affected participants’ voting intention.Research limitations/implicationsBeing based on a questionnaire that asked participants about how they perceive different aspects of social media, the present study is limited to their perceptions. Therefore, further studies covering the voters’ behaviour in action could be efficient complements to the present study.Practical implicationsThe findings could guide the political parties into prioritizing the aspects of social media in forming an effective campaign resulting in being elected.Social implicationsThe findings have the potential to help the public in making better informed decisions when voting. Furthermore, the results of this study indicate applications for social media which are beyond leisure time fillers.Originality/valueFuzzy logic and multidimensional panel data estimates are this study’s novelty and originality. Structural equation modelling and crisp linguistic values have been used in previous studies on social media’s effect on voting intent. The former refines the data gathered from a questionnaire, and the latter considers the possibility of including different grouping factors to achieve a more efficient and less biased estimation.

Identification of medium- and mechanism-related pitfalls towards improved performance and applicability of electrochemical mercury(II) aptasensors.

The importance of understanding the mercury (II) ion interactions with thymine-rich DNA sequences is the reason for multiple comparative investigations carried out with the use of optical detection techniques directly in the depth of solution. However, the results of such investigations have limited applicability in the interpretation of the Hg2+ binding phenomenon by DNA sequences in thin, interfacial (electrode/solution), self-organized monolayers immobilized on polarizable surfaces, often used forsensing purposes in electrochemical biosensors. Overlooking the careful optimization of the measurement conditions is the source of discrepancies in the interpretation of the registered electrochemical signal. In this study, the chosen effects accompanying the efficiency of surface related recognition of Hg2+ by polyThymine DNA sequences labelled with methylene blue were investigated by voltammetry, QCM and spectro-electrochemical techniques. As was shown, the composition of the biosensing layer and buffers or the analytical procedures have a significant impact on the registered electrochemical readout which translates into signal stability, the biosensor's working parameters or even the mechanism of detection. After elucidation of the above factors, the complete and ready-to-use biosensor-based analytical solution was proposed offering subpicomolar mercury ion determination with high selectivity (also in aqueous real samples), reusability, and high signal stability even after long-term storage. The developed procedures were successfully used during the miniaturization process with self-prepared (PVD) elastic transducers. The obtained sensor, together with the simplicity of its use, low manufacturing cost, and attractive analytical parameters (i.e., LOD < < Hg2+ WHO limit) can present an interesting alternative for on-site mercury ion detection in environmental samples.

Electropolymerized Bipolar Poly(2,3-diaminophenazine) Cathode for High-Performance Aqueous Al-Ion Batteries with An Extended Temperature Range of -20 to 45°C.

Achieving reversible insertion/extraction in most cathodes for aqueous aluminum ion batteries (AAIBs) is a significant challenge due to the high charge density of Al3+ and strong electrostatic interactions. Organic materials facilitate the hosting of multivalent carriers and rapid ions diffusion through the rearrangement of chemical bonds. Here, a bipolar conjugated poly(2,3-diaminophenazine) (PDAP) on carbon substrates prepared via a straightforward electropolymerization method is introduced as cathode for AAIBs. The integration of n-type and p-type active units endow PDAP with an increased number of sites for ions interaction. The long-range conjugated skeleton enhances electron delocalization and collaborates with carbon to ensure high conductivity. Moreover, the strong intermolecular interactions including π-π interaction and hydrogen bonding significantly enhance its stability. Consequently, the Al//PDAP battery exhibits a large capacity of 338 mAh g-1 with long lifespan and high-rate capability. It consistently demonstrates exceptional electrochemical performances even under extreme conditions with capacities of 155 and 348 mAh g-1 at -20 and 45°C, respectively. In/ex situ spectroscopy comprehensively elucidates its cation/anion (Al3+/H3O+ and ClO4 -) storage with 3-electron transfer in dual electroactive centers (C═N and -NH-). This study presents a promising strategy for constructing high-performance organic cathode for AAIBs over a wide temperature range.

Synthesis and characterisations of clinoptilolite enriched hydroxyapatite nanoceramics by sol-gel route for bone regeneration

Hydroxyapatite (HA) has great bioactive potential in bone tissue engineering (BTE). However, the high crystalline stability of synthetic HA restricts its in-vivo bioresorbability which extends the healing time of bone defects. This study investigates doping HA with biocompatible Clinoptilolite (CLP) mineral rich in silicate and other biomimetic ions (Na+, K+, Ca+2, Mg+2 etc.). Sol-gel-based CLP doped HA nanoceramics are aimed to be exploited as bone filler substitutes with biomimetic morphology, composition, and improved biocompatibility and bioactivity. The pure and CLP (5%, 10% and 20%) doped HA ceramics were synthesised by sol-gel method to provide molecular level interactions of ions and sintered at different temperatures (800 °C, 950 °C, and 1100 °C). Morphological analyses by SEM and S-TEM showed biomimetic nano rod-like HA particles are attached to dispersed CLP sheets. Sintering of composite ceramics led to a cell-friendly interconnected porous microstructure even at 1100 °C, where the pure HA had a compact non-porous structure. The Ca/P ratio of CLP-doped HA samples was lower than the stoichiometric HA which indicates a partial reduction of stability that is supposed to induce bioresorption capacity. Cytotoxicity tests by WST-8 with Saos-2 cell lines showed that CLP addition into HA has significantly improved cell viability. The HA-CLP nanoceramics are expected to promote bone regeneration due to cell-friendly microstructure and biomimetic composition which can be supported by further in-vivo clinical studies.

Synthesis, structural and optical characterization of CdxZn1−xS/FNBRnanocomposites

AbstractCdxZn1−xS nanoparticles have been synthesized on the base of functionalized nitrile butadiene rubber (FNBR) by SILAR method and characterized by various techniques. Both binary and ternary sulfide nanocrystals have been obtained in the cubic phase with very high purity at room temperature. The average particle size decreased from 2.49 nm to 2.22 nm and then increased to 2.44 nm by the increasing of zinc concentration from 25 % to 50 % and 75 %. The calculated Young's modulus for (111), (220) and (311) planes are 97.84, 78.51 and 64.33 m2 N−1 for CdS and 95.84, 69.68, 53.42 m2 N−1 for ZnS, respectively. The band corresponding PO32− (977 cm−1) shifted to 969, 975, 972, 973, and 972 cm−1 upon the formation of CdS, ZnS, Cd0.5Zn0.5S, Cd0.75Zn0.25S and Cd0.25Zn0.75S nanoparticles into FNBR matrix, which is explained by Hooke's Law. EPR spectra of CdS/FNBR nanocomposite show broad and singlet asymmetric, isotropic symmetry (gx=gy=gz). The appearance of a new line in the 3518 G magnetic field is observed in both CdS and Cd0.5Zn0.5S compounds’ spectra.The total mass loss of the samples NBR, FNBR, Cd2+ and Zn2+ ions containing FNBR are 93.76, 59.77, 60.03 and 57.79 %, respectively. High crystallinity is caused by complete interaction of metal ions with functional groups during the nucleation.

The ion cyclotron parametric instabilities and the anomalous heating of ions in the scrape-off layer of tokamak plasma in the high harmonic fast wave heating regime

The electrostatic parametric instabilities of a plasma, driven by the high harmonic fast wave (HHFW) with frequency at ion cyclotron (IC) harmonics of order 30–50 are investigated numerically. The derived numerical results are consistent with parametric decay of HHFW into the high harmonic IC (Bernstein) wave and an unobserved IC quasimode under conditions of the negligible small electron Landau damping. The detected instability develops in the finite interval of the HHFW wavelength along the toroidal magnetic field. The development of this ion kinetic quasimode decay instability is accompanied by the anomalous anisotropic heating of ions, resulted from the interaction of ions with IC parametric turbulence. It was found that the anomalous heating rate of ions across the magnetic field is much larger than the heating rate of ions along the magnetic field. The anisotropic heating of the scrape-off layer ions was observed on the National Spherical Torus Experiment experiments with HHFW heating and current drive at IC harmonics of order 10 [G. Taylor et al. Phys. Plasmas 17, 056114 (2010), and J. Hosea et al. Phys. Plasmas 15, 056104 (2008)]. The derived results predict that these experimental results will be reproduced qualitatively in the experiments with HHFW heating and current drive using HHFW at IC harmonics of order 30–50.

Speciation studies of a Bisphosphonate Drug. New thermodynamic insights of Sodium Alendronate with Ca2+ and Mg2+ in NaCl aqueous solution (0.10 ≤ I/mol kg-1 ≤ 1.02)

The thermodynamics of interaction of a second-generation bisphosphonate drug, 4-amino-1-hydroxy-1-phosphonobutyl phosphonic acid mono sodium (sodium alendronate) with H+, Ca2+ and Mg2+ has been investigated. The protonation constants were determined in NaCl and (C2H5)4NI aqueous solutions at different ionic strengths (0.10 ≤ I/mol kg-1(H2O) ≤ 1.02) and temperatures (288.15 ≤ T/K ≤ 310.15) by using the ISE-[H+] potentiometry. The differences of the log KiH in the two ionic media were interpreted in terms of activity coefficient variations and formation of Na+ weak complexes. The interactions with Mg2+ and Ca2+ were studied in NaCl(aq) (0.10 ≤ I/ mol kg-1 (H2O) ≤ 1.02) and T = 298.15 K. Two different speciation models were obtained; Ca2+: CaH2L, CaHL, CaL. Mg2+: MgH3L, MgH2L, MgHL, MgL. The dependence of the thermodynamic parameters on the ionic strength and temperature was modelled by means of the Specific Ion Interaction Theory (SIT) and a modified Debye-Hückel equation including a term for the dependence on T/K. The first two protonation equilibria are exothermic, and the reactions are not favoured by an increase of the temperature whilst the last two are endothermic. The entropic contribution resulted to be the driving force of the reactions. The sequestering ability of alendronate towards the two metal cations was quantified by means of the pL0.5 parameter calculated at different pHs and ionic strengths. It resulted that alendronate has a higher sequestration toward Mg2+ with respect to Ca2+. A simulation of the alendronate behaviour in human blood plasma was carried out.

Metal Ion-Regulated Fluorescent Sensor Array Based on Gold Nanoclusters for Physiological Phosphate Sensing.

The detection of physiological phosphates (PPs) is of great importance due to their essential roles in numerous biological processes, but the efficient detection of different PPs simultaneously remains challenging. In this work, we propose a fluorescence sensor array for detecting PPs based on metal-ion-regulated gold nanoclusters (AuNCs) via an indicator-displacement assay. Zn2+ and Eu3+ are selected to assemble with two different AuNCs, resulting in quenching or enhancing their fluorescence. Based on the competitive interaction of metal ions with AuNCs and PPs, the fluorescence of AuNCs will be recovered owing to the disassembly of AuNC-metal ion ensembles. Depending on different PPs' distinct fluorescence responses, a four-channel sensor array was established. The array not only exhibits good discrimination capability for eight kinds of PPs (i.e., ATP, ADP, AMP, GTP, CTP, UTP, PPi, and Pi) via linear discriminant analysis but also enables quantitative detection of single phosphate (e.g., ATP) in the presence of interfering PPs mixtures. Moreover, potential application of the present sensor array for the discrimination of different PPs in real samples (e.g., cell lysates and serum) was successfully demonstrated with a good performance. This work illustrates the great potential of a metal ion-regulated sensor array as a new and efficient sensing platform for differential sensing of phosphates as well as other disease-related biomolecules.

Induced Isotensor Interactions in Heavy-Ion Double-Charge-Exchange Reactions and the Role of Initial and Final State Interactions

The role of initial state (ISI) and final state (FSI) ion–ion interactions in heavy-ion double-charge-exchange (DCE) reactions A(Z,N)→A(Z±2,N∓2) are studied for double single-charge-exchange (DSCE) reactions given by sequential actions of the isovector nucleon–nucleon (NN) T-matrix. In momentum representation, the second-order DSCE reaction amplitude is shown to be given in factorized form by projectile and target nuclear matrix elements and a reaction kernel containing ISI and FSI. Expanding the intermediate propagator in a Taylor series with respect to auxiliary energy allows us to perform the summation in the leading-order term over intermediate nuclear states in closure approximation. The nuclear matrix element attains a form given by the products of two-body interactions directly exciting the n2p−2 and p2n−2 DCE transitions in the projectile and the target nucleus, respectively. A surprising result is that the intermediate propagation induces correlations between the transition vertices, showing that DSCE reactions are a two-nucleon process that resembles a system of interacting spin–isospin dipoles. Transformation of the DSCE NN T-matrix interactions from the reaction theoretical t-channel form to the s-channel operator structure required for spectroscopic purposes is elaborated in detail, showing that, in general, a rich spectrum of spin scalar, spin vector and higher-rank spin tensor multipole transitions will contribute to a DSCE reaction. Similarities (and differences) to two-neutrino double-beta decay (DBD) are discussed. ISI/FSI distortion and absorption effects are illustrated in black sphere approximation and in an illustrative application to data.

Unraveling the Microscopic Mechanism of Molecular Ion Interaction with Monoclonal Antibodies: Impact on Protein Aggregation.

Understanding and predicting protein aggregation represents one of the major challenges in accelerating the pharmaceutical development of protein therapeutics. In addition to maintaining the solution pH, buffers influence both monoclonal antibody (mAb) aggregation in solution and the aggregation mechanisms since the latter depend on the protein charge. Molecular-level insight is necessary to understand the relationship between the buffer-mAb interaction and mAb aggregation. Here, we use all-atom molecular dynamics simulations to investigate the interaction of phosphate (Phos) and citrate (Cit) buffer ions with the Fab and Fc domains of mAb COE3. We demonstrate that Phos and Cit ions feature binding mechanisms, with the protein that are very different from those reported previously for histidine (His). These differences are reflected in distinctive ion-protein binding modes and adsorption/desorption kinetics of the buffer molecules from the mAb surface and result in dissimilar effects of these buffer species on mAb aggregation. While His shows significant affinity toward hydrophobic amino acids on the protein surface, Phos and Cit ions preferentially bind to charged amino acids. We also show that Phos and Cit anions provide bridging contacts between basic amino acids in neighboring proteins. The implications of such contacts and their connection to mAb aggregation in therapeutic formulations are discussed.