Positive Potential Region Research Articles

Packaging and pH Effects on Meat Discoloration through Electrochemistry

Myoglobin is the sarcoplasmic heme protein that determines the color of the meat. The oxidation state of myoglobin results in different forms of myoglobin, such as deoxy-, oxy-, and metmyoglobin. As the deviation from the bright red color of beef affects consumers' purchase decisions, meat packaging is done to retain the meat color and delay spoilage. In these studies, UV-spectrophotometric analysis is combined with the electrochemical method. Meat packaged under different conditions was considered. Two packaging conditions, vacuum and polyvinyl chloride, were compared with the normal unpackaged sarcoplasmic beef sample. Electrochemical regions of both positive and negative potential were diagnosed for sensory peaks where the data of vacuum packaging implied more color stability. To assess the effect of pH on meat discoloration, pH conditions of the physiological state (pH 7.4) and post-mortem meat (pH 5.6) were mainly considered. The rate of meat discoloration was higher at pH 5.6 than at pH 7.4. Electrochemical insights with regard to various packaging effects on meat discoloration will be discussed further.

A protonated imine-based water-soluble cadmium complex with N, O donor chelating agent: Synthesis, structure, fluorescence efficiency and catecholase activity

A mononuclear air-stable and water soluble six coordinated cadmium (II) complex [Cd(HL)6](ClO4)2 (1) with bi-dentate phenol based ligand [HL = 2-(benzylimino)methyl)phenol] have been synthesized. The complex has been characterized by various spectroscopic techniques. The solid-state structure, by single crystal X-ray diffraction, revealed that Cd(II) complex crystallizes in trigonal space group R-3. Interestingly, single crystal X-ray structure data show that the Schiff base in the complex is present in a zwitterionic form and coordinated through the phenolic oxygen atom only, providing the first example of more than four monodendate Schiff base in zwitterionic form to be coordinated with the central metal ion. Cyclic voltamogram of the cadmium (II) complex (1) exhibits a quasi-reversible oxidation peak in the positive potential region. The redox process occurs due to the generation of phenoxyl radical from the pheolate group of the attached ligand with the central metal ion. Luminescence spectra show a strong emission band around 500 nm. Additionally, the mononuclear cadmium complex (1) shows catechol oxidase activity in methanol under aerobic conditions. The turnover number of the process is 2.766 × 103 h–1. The oxidation process occurs via formation of ligand oriented phenoxyl radical species.

An Analysis of the Instability Conditions and Water Vapor Transport Characteristics during a Typical Rainstorm in the Tarim Basin

In order to deepen the understanding of the occurrence mechanism and water vapor transport characteristics of the heavy rain process in the extreme arid region of Xinjiang, a rare heavy rain process in the Tarim Basin during the period of 18–22 July 2021 was comprehensively analyzed by using multi-source data. The results show that the upper tropospheric South Asian high was distributed in a “west-high-east-low” pattern during the rainstorm process, and the rainstorm area was located on the right side of the upper jet stream entrance area, while the middle-level Iranian high pressure, Baikal high pressure and Central Asian low pressure formed a “two-highs and one-low” circulation situation. The coupling of the high and low air jets and the strong vertical upward motion provided favorable dynamic conditions. Rainstorm water vapor mainly comes from the Mediterranean Sea, Central Asia and the Indian Ocean, and it enters the basin in four paths: west, east to west, west to east, and southwest and south. The water vapor mainly flows into the middle layer of the western boundary and the southern boundary and the lower layer of the eastern boundary, and it flows out from the middle and upper layer of the eastern boundary. The negative moist potential vorticity region at a low level has a strong indicator significance for the occurrence and development of heavy rain, and the superposition of positive and negative moist potential vorticity regions at vertical height is conducive to the occurrence and development of heavy rain.

From 'halogen' to 'tetrel' bonds: matrix isolation IR spectroscopic and quantum mechanical studies of the effect of central atom substitution in donor tetrahalogens on binary complex formation with formic acid.

Binary complex formation between silicon tetrachloride (SiCl4) and formic acid (FA) has been observed in an argon matrix environment. Such complex formation manifests as spectral shifts in signature vibrations of the latter, namely the νCO, νC-O and νO-H vibrations. Quantum chemical calculations reveal that the most stable conformers of the complex involve predominantly the tetrel bond, which has been defined in existing literature as a variant of the "σ-hole" interactions. Here, regions of positive electrostatic potential on the tetrahedral face of SiCl4 act as electrophilic centers (σ-hole) to which the nucleophilic carbonyl group of FA is able to bind. Atoms-in-molecules analysis predicts a bond critical point along the non-covalent contact between the tetrel atom Si and the carbonyl oxygen on FA, corroborating the presence of the tetrel bond. The hyperconjugative interaction parameters at the binding interface obtained from Natural Bond Orbital (NBO) analysis are also consistent with such observations. Although apparently similar to SiCl4, there are noticeable differences in the binding preferences of the lower homologue carbon tetrachloride (CCl4). The binary complexes of the latter with the same FA acceptor molecule have been previously shown to involve halogen bonded, rather than tetrel bonded interactions (Banerjee and Bhattacharya, Spectrochim. Acta Mol. and Biomol. Spectrosc., 2021, 250, 119355). Such variations in the nature of non-covalent interactions of these tetrahalogens are attributed to differences in the distribution of electronic charge density surrounding the central tetrel atom, as obtained from mappings of their electrostatic potential surfaces. Our combined experimental and theoretical findings therefore provide direct evidence of the growing propensity of tetrel atoms to engage in tetrel bonding as we move lower down Group 14, and re-assert the reluctance of the smaller and more electronegative carbon atom to serve as a tetrel bond participant.

Novel nitrogen-doped carbon-coated SnSe2 based on a post-synthetically modified MOF as a high-performance anode material for LIBs and SIBs.

SnSe2 with high theoretical capacity has been identified as an emerging anode candidate for lithium-ion batteries (LIBs) and sodium-ion batteries (SIBs). However, the rate performance and cycling performance of this material in practical applications are still limited by unavoidable volume expansion and low conductivity. In this work, we designed and synthesized nitrogen-doped carbon-coated SnSe2/C-N composites using 2-aminoterephthalic acid (C8H7NO4) as a nitrogen-containing compound for modification by hydrothermal and vacuum calcination methods to achieve efficient utilization of active sites and optimization of the electronic structure. The carbon skeleton inherited from the Sn-MOF precursor can effectively improve the electronic conduction properties of SnSe2. N-doping in the Sn-MOF can increase the positive and negative electrostatic potential energy regions on the molecular surface to further improve the electrical conductivity, and effectively reduce the binding energy with Li+/Na+ which was determined by Density Functional Theory (DFT) methods. In addition, the N-doped carbon skeleton also introduces a larger space for Li+/Na+ intercalation and enhances the mechanical properties. In particular, the post-synthetically modified MOF-derived SnSe2/C-N materials exhibit excellent cyclability, with a reversible capacity of 695 mA h g-1 for LIBs and 259 mA h g-1 for SIBs after 100 cycles at 100 mA g-1.

Electrochemistry of Flavonoids.

This review presents a description of the available data from the literature on the electrochemical properties of flavonoids. The emphasis has been placed on the mechanism of oxidation processes and an attempt was made to find a general relation between the observed reaction paths and the structure of flavonoids. Regardless of the solvent used, three potential regions related to flavonoid structures are characteristic of the occurrence of their electrochemical oxidation. The potential values depend on the solvent used. In the less positive potential region, flavonoids, which have an ortho dihydroxy moiety, are reversibly oxidized to corresponding o-quinones. The o-quinones, if they possess a C3 hydroxyl group, react with water to form a benzofuranone derivative (II). In the second potential region, (II) is irreversibly oxidized. In this potential region, some flavonoids without an ortho dihydroxy moiety can also be oxidized to the corresponding p-quinone methides. The oxidation of the hydroxyl groups located in ring A, which are not in the ortho position, occurs in the third potential region at the most positive values. Some discrepancies in the reported reaction mechanisms have been indicated, and this is a good starting point for further investigations.

Theoretical investigation of asphaltene molecules in crude oil viscoelasticity enhancement

Understanding the mechanisms of viscosity enhancement in crude oil phases is crucial for optimizing extraction and transportation processes. The enhanced viscosity mechanism of crude oil phase can be attributed to the intricate intermolecular interactions between asphaltene molecules. However, the molecular mechanism of the viscosification of asphaltene molecules in crude oil is not yet to be fully understood. In this work, molecular dynamics simulations were employed to investigate the dynamic behavior and viscosification mechanism of asphaltene molecules in complex oil phases. Research suggests that the neutral surface of asphaltenes features abundant positive and negative electrostatic potential regions, facilitating complementary pairing between these areas. This significantly augments electrostatic interactions among asphaltene molecules. Besides, the expansive nonpolar expanse on the normal asphaltene surface facilitates interactions between asphaltenes and crude oil molecules. This leads the crude oil viscosity of the system containing normal asphaltene is higher than that of the system containing acidic asphaltene under the same mass fraction (382 μ Pa·s for AAsp and 416 μ Pa·s for NAsp). This work provides insight into the viscosity enhancement mechanisms in crude oil phases and is helpful in improving the efficiency of crude oil extraction and transportation.

Electrodeposition of Ti in Molten Alkali Metal Fluoride–Chloride Mixtures: Comparative Study of Li, Na, K, and Cs Systems

1. IntroductionTitanium (Ti) is a metal with excellent properties such as high corrosion resistance and biocompatibility. However, it is still not widely used due to its high production cost and poor workability. If Ti films can be plated on a variety of substrates, the excellent surface properties of Ti can be imparted, and it is expected to be applied in a wider range of fields.We have previously studied Ti electrodeposition using KF–KCl [1-3] and LiF–LiCl [4,5] melts and reported that smooth Ti films were obtained. Here, fluoride–chloride melts containing a single cation, such as KF–KCl and LiF–LiCl, were used so that differences due to cations could be compared. As a result, we have already reported that the electrodeposition potential of Ti differs significantly between the K- and Li-based systems [4]. Therefore, in this study, we investigated the electrodeposition of Ti and the electrochemical behavior of Ti(III) ions in the CsF-CsCl and NaF-NaCl melts. This allowed us to systematically compare the effects of cations on titanium electrodeposition for the Li-, Na-, K-, and Cs-based systems.2. ExperimentalThe experiments were conducted in eutectic CsF–CsCl and NaF–NaCl melts in an Ar glove box. A2TiF6 (A = Cs, Na) and sponge Ti were added to the melts and Ti(IV) ions were converted to Ti(III) ions by comproportionation reaction. Ni plate, Mo and Au flag electrodes were used as the working electrodes. The counter and reference electrodes were Ti rods. The potential of the reference electrode was calibrated by A+/A (A = Cs, Na) potential measured at a Mo electrode. The electrochemical behavior of Ti(III) was studied by cyclic voltammetry. Samples prepared by galvanostatic electrolysis of Ni plate substrates were analyzed by X-ray diffraction (XRD) after washing with distilled water.3. Result and DiscussionFigure 1 (a) shows cyclic voltammograms measured at a Mo flag electrode in the negative potential region in molten CsF–CsCl at 823 K. After the addition of Ti(III) ions, cathodic currents around 0.3 V were larger than those before the addition, and a current shoulder was observed at 0.3 V. Furthermore, a sample prepared by galvanostatic electrolysis at a cathodic current density of 25 mA cm−2 was confirmed to be Ti metal by XRD. Considering that the potential during the electrodeposition was around 0.3 V, the cathodic currents around 0.3 V in the CV were confirmed to beTi(III) + 3e− → Ti(0).Figure 1 (b) shows cyclic voltammograms measured at a Au flag electrode in the positive potential region in molten CsF–CsCl containing Ti(III) ions at 823 K. A pair of redox currents were observed around 1.7 V. The number of electrons transferred was 0.86 which was calculated from the difference in the cathodic and anodic peak potentials. This result indicates that the redox reaction around 1.7 V isTi(IV) + e− ⇄ Ti(III).Here, the formal potential of Ti(IV)/Ti(III) was calculated to be 1.63 V from the average values of the cathodic and anodic peak potentials.We compared the obtained potentials of Ti(III)/Ti(0) and Ti(IV)/Ti(III) to those previously reported in KF–KCl and LiF–LiCl melts [2,4]. Figure 2 shows the comparison of the Ti(III)/Ti(0) and Ti(IV)/Ti(III) potentials in CsF–CsCl, KF–KCl, and LiF–LiCl melts. All potentials were calibrated using F2/F− potential for comparison because Ti(III) ions exist as fluoro-complexes in the melts. Both Ti(III)/Ti(0) and Ti(IV)/Ti(III) potentials were negative in the order of Li-, K-, Cs-based systems. Such potential differences are explained by the interactions of alkaline cations (A+) and fluoride ions (F−); smaller cations interact more strongly with F−, resulting in reduced stability of Ti fluoro-complexes. At the meeting, we will compare and discuss all the results, including those obtained with NaF-NaCl melts.AcknowledgmentA part of this work was supported by JSPS KAKENHI Grant Number 22K14507. A part of this study was conducted as a collaboration with Sumitomo Electric Industries, Ltd.

Robust electrolytic oxygen evolution at nanostructured NiFe LDH@ in-situ functionalized graphite felt

NiFe layered double hydroxide (LDH) is among the most effective electrocatalysts for oxygen evolution reaction (OER). Tailor-designed NiFe LDH with high electronic conductivity assists in facile hydrogen production with marked energy-saving. Graphite felt (GF), a 3-D porous substrate with excellent conductivity is used herein. However, its low hydrophilicity calls for pretreatment. Herein, the potential strength of electrochemistry is applied to enhance the hydrophilicity of GF surface during the deposition of homogenous uniform distributed NiFe LDH electrocatalyst. GF is sequentially modified by sweeping the potential from the oxidative to the reductive region in a solution containing 100 mM NiSO4 and 30 mM FeCl3. Carbon structure flaws are introduced at the positive potential region. whereas during the negative potential scan, hydrogen evolution occurs with simultaneous uniform and homogeneous deposition of NiFe LDH. SEM, HR-TEM, mapping EDX, XPS, XRD, and contact angle measurements are utilized to reveal the features of the functionalized GF with NiFe LDH deposits. Furthermore, FeOOH/GF and Ni(OH)2/GF electrodes are prepared to highlight the advantages of the binary NiFe LDH/GF electrode toward the OER. Interestingly, the NiFe LDH/GF enhances the OER in an alkaline medium by throwing up a low overpotential of 273 mV to support a current density of 10 mA cm−2 alongside a Tafel slope of 48.5 mV dec−1. Furthermore, the NiFe LDH shows marked stability for 24 h of ongoing electrolysis. Therefore, the designed catalyst can be worked as an efficient anode for water electrolysis.

Phase transfer mechanisms of fluorophore-labeled cell-penetrating peptide ε-poly-l-α-lysine at liquid|liquid interfaces

The transfer reaction of a novel cell-penetrating peptide, ε-poly-l-α-lysine (εPL) as a bacterial polycationic isopeptide, was investigated at the water|1,2-dichloroethane (DCE) interface. Spectroelectrochemical analysis elucidated the interfacial reaction mechanism of covalently carboxyfluorescein (FAM)-labeled εPL (FAM-εPL) in detail. FAM-εPL showed the concentration-dependent interfacial mechanisms in the positive potential region, i.e., the adsorption from the aqueous side of the interface was occurred at the low concentration of FAM-εPL, while the ion transfer across the interface accompanied by the adsorption process at the organic side proceeded further as the concentration increased. The facilitated ion transfer of FAM-εPL was observed at the biomimetic interface with a phospholipid layer. The transfer process of FAM-εPL was accelerated by the specific interaction at the aqueous side of the biomimetic interface, that is, the polar headgroup region of the phospholipid layer. The interfacial and membrane permeation mechanisms of εPL were elucidated through the spectroelectrochemical measurements by the fluorescent FAM modification and the phase transfer of a membrane impermeable FAM was also achieved by forming the conjugate with εPL.

Built-in electric field accelerates photogenerated carrier separation in vanadium-oxygen doped C3N4 for flash degradation of methylene blue: Experimental and molecular simulations

Flash photodegradation of organic pollutants at high concentrations is an urgent need for industrial organic wastewater treatment. Situ high-energy wet ball milling is adopted to fabricate the vanadium-oxygen doped carbon nitride catalysts to implement the flash degradation of methylene blue (MB). The experimental results indicated that the photocatalyst degradation ratio of MB was higher than 90% in 3 min under visible-light irradiation 300 W, catalyst dosage 0.2 g/L and MB concentration of 100 mg/L. MB removal rate was nearly 20 times higher than that of primitive carbon nitride. Vanadium-oxygen doping was beneficial to the reduction of band gap less than 2.0 eV and the formation of built-in electric field. It is notable notice that both valence band and conduction band of catalyst were tuned to be in positive potential region, benefiting for holes (h+) formation to boost the flash degradation of contaminants. Strong electrophilic attack of h+ caused the bonds of C-S+=C and CN-C broken, triggering the aromatic ring opened to decompose into smaller molecules.

XeF2 Coordination Complexes of the [BrO2]+ Cation, [O2Br(FXeF)n][AsF6] (n = 1, 2) and [O2Br(FXeF)2][SbF6]; Their Syntheses and Structural Characterizations.

The syntheses and structural characterizations of the first XeF2 coordination complexes of the [BrO2]+ cation are described. The reactions of [BrO2][PnF6] (Pn = As, Sb) with XeF2 in anhydrous HF solvent yield the salts [O2Br(FXeF)n][AsF6] (n = 1, 2) and [O2Br(FXeF)2][SbF6], which were characterized by low-temperature (LT) Raman spectroscopy and single-crystal X-ray diffraction (SCXRD). The XeF2 ligands and [PnF6]- coordinate to the Lewis acidic [BrO2]+ cation through primarily electrostatic BrV---FXe σ-hole bonds that result from coordination of the F atoms into regions of high positive electrostatic potential on the Br(V) atom and have bond trajectories that avoid the stereoactive valence electron lone-pair of Br(V). The complexes and their structural characterizations by LT Raman spectroscopy and SCXRD significantly extend the coordination chemistry of Br(V) and provide rare examples of a noble-gas difluoride coordinated to a strong oxidant main-group Lewis acid center.

Electronic structure modulation of g-C3N4 by Hydroxyl-grafting for enhanced photocatalytic peroxymonosulfate Activation: Combined experimental and theoretical analysis

Graphitic carbon nitride(g-C3N4) materials own the characteristics of metal-free, low cost, and flexible surface modification. However, the defect of high photo-generated electron-hole recombination rate greatly limits its photocatalytic performance. In this paper, hydroxyl-grafting g-C3N4 (CN-OH) was prepared by a simple hydrothermal method. Photocatalytic experiments showed that CN-OH exhibited excellent performance and stability in activating peroxymonosulfate (PMS). 1O2 was the main reactive oxygen species in CN-OH/PMS/Vis system. Hydroxyl-grafting realized the modulation of electronic structure, which caused the reduction of photo-generated electron-hole recombination and the promotion of interfacial electron transfer. Combining experiments and theoretical calculations, the mechanism of its photocatalytic PMS activation was put forward from two aspects: the oxidation process at the positive electrostatic potential region and the reduction process at the negative. The findings provided a valuable reference for the development of efficient photocatalysts through a simple surface modification strategy.

Monolayer-Protected Gold Nanoparticles Functionalized with Halogen Bonding Capability─An Avenue for Molecular Detection Schemes.

The use of functionalized nanoparticles (NPs) and their aggregation in the presence of a targeted analyte is a well-established molecular detection strategy predicated on harnessing specific molecular interactions to the NP periphery. Molecules able to specifically interact with the functionalized NPs alter the unique optical and electrochemical properties of the NPs as a function of interparticle spacing. While many intermolecular interactions have been successfully exploited in this manner in conjunction with aqueous NP systems, the use of non-aqueous NPs in the same capacity is significantly less explored. A fundamental interaction that has not been previously investigated in NP schemes is halogen bonding (XB). XB is an orthogonal, electrostatic interaction between a region of positive electrostatic potential (δ+) on a halogen atom (i.e., XB donor) and a negative (δ-) Lewis base (XB acceptor) molecule. To couple XB with NP systems, ligands featuring a molecular structure that promotes XB interactions need to be identified, optimized, and synthesized for subsequent attachment to NPs. Herein, density functional theory (DFT) and NMR techniques are used to identify a strong XB-donor moiety (-C6F4I) and a synthetic scheme for a thiolate ligand featuring that functionality is devised and executed with high purity/yield (78%). Ligand-exchange reactions allow functionalization of non-aqueous alkanethiolate-protected gold NPs or monolayer-protected clusters (MPCs) with the XB-donor ligands. Functionalized MPCs (f-MPCs), within both assembled films and in solution, are shown to engage in XB interactions with target XB-acceptor molecules. Molecular recognition events, including induced aggregation of the f-MPCs, are characterized with UV-vis spectroscopy, cyclic voltammetry, TEM imaging, and diffusion-ordered spectroscopy NMR with limits of detection of 50-100 nM for strong XB acceptors. While fundamental exploration of XB interactions is ongoing, this study represents a step toward utilizing XB within molecular detection schemes, an application with implications for supramolecular chemistry, forensic, and environmental chemical sensing.

Electrochemistry of icosahedral metal full and half sandwich metallacarboranes in phosphate buffers

• Electrochemistry of sandwich (Cr, Fe Co, Ni) metallacarbores in aqueous solution. • The electrochemical process connected with metal atom is reversible. • Electrochemical processes connected with the boron cage are irreversible. Electrochemical behavior of metallacarboranes containing different central coordination atoms – Co, Cr, Ni and Fe – in aqueous phosphate buffers is described in this study. Also, the effects of number of the dicarbaborane ligands present in the metallacarborane and the influence of mixed or polydecker sandwich structure on the electrochemical activity were studied. In general, we found two distinctive regions of electrochemical activity. One of them is located in the negative potential range and corresponds to redox process on the central metal atom. The second one is located in the positive potential region and is connected to core cage oxidation process. The results revealed clearly promising properties of majority of studied metallacarboranes to be used as electrochemical tags in aqueous solutions, with potentially better properties that the known and widely studied cobalt bis(dicarbollide)(1-) ion based systems.

Quantitative Investigation of Halogen and Hydrogen Bonding in 2‐Chloro, 4‐X‐Benzoic Acids

AbstractThe crystal structure, Hirshfeldsurface analysis, topological analysis of the electron density and total interaction energies of four compounds, 2‐Chloro, 4‐X‐Benzoic Acids (where X=I, Br, Cl and F) have been analysed. The packing similarity was evaluated in all compounds using theXPacanalysis. The qualitative information about intermolecular interactions is derived from the crystal structure and Hirshfeld surface analyses whereas quantitative information are determined by the QTAIM analysis as well as total interaction energies fromCrystalExplorer. The topological properties are estimated for all compounds in both crystal geometry and gas phase usingTOPONDandAIMALL, respectively. The carboxylic acid O−H⋅⋅⋅O HB dimers, C−H⋅⋅⋅O HBs and Cπ⋅⋅⋅Cπaromatic stacking interactions are found to be common interactions in all compounds. The topological properties and bond paths demonstrate them as non‐covalent stabilizing interactions in the crystalline state. The hierarchy of interactions concerning their strength is observed in the following order such that O−H⋅⋅⋅O HB dimers>Cπ⋅⋅⋅Cπaromatic stacking interactions>C−H⋅⋅⋅O HBs>Type II X⋅⋅⋅Cl interactions and C−H⋅⋅⋅Cl HBs>Type I homo‐halogen X⋅⋅⋅X interactions in all compounds. Additionally, the strength of Type I homo‐halogen X⋅⋅⋅X interactions vary in the order: I⋅⋅⋅I>Br⋅⋅⋅Br>Cl⋅⋅⋅Cl>F⋅⋅⋅F. The hierarchy of interactions is further supported by molecular electrostatic potential surfaces associated with both positive and negative potential regions.

Single crystal XRD and DFT investigation of 1,5-dimethyl-4-[(2-oxo-1,2-diphenylethylidene) amino]-2-phenyl-1,2-dihydro-3H-pyrazol-3-one

The single crystal 1,5-dimethyl-4-[(2-oxo-1,2-diphenylethylidene) amine]-2-phenyl-1,2-dihydro-3H-pyrazol-3-one [DDAPDP] was designed to enhance luminescence property using benzil and 4-aminoantipyrine. DFT calculations of DDAPDP were done with Gaussian 16 W program employing hybrid functional B3LYP with 6–311++G (d,p) basis set for geometry optimization without symmetry constraints. The single crystal was studied based on theoretical aspects such as Frontier Molecular Orbital (FMO), Natural Bond Orbital (NBO), Mullikan atomic charge and Molecular Electrostatic Potential (MEP) using density functional method. The experimental and theoretical spectral analysis of the single crystal system was investigated using FTIR, Raman, UV –visible, 1H NMR and 13C NMR techniques. Positive electrostatic potential regions dispersed throughout the rings and represent possible nucleophilic attack sites, whereas negative electrostatic potential regions are typically grouped around the CO group. Energy gap −3.776391 eV, confirmed by the estimated HOMO and LUMO energies. Natural bond orbital analysis (NBO) was used to assess the molecule's stability as a result of charge delocalization and hyper conjugation. Electron population of each atom was calculated by Mulliken atomic charge distribution analysis. The bacterium E. coli (Gram negative) and the organism S. aureus, together with a standard medication, were used to study and assess the compounds' antimicrobial activity in vitro, which reveals the antibacterial and antifungal activities of DDAPDP.

On the Importance of Halogen Bonding Interactions in Two X-ray Structures Containing All Four (F, Cl, Br, I) Halogen Atoms

This manuscript reports the synthesis and X-ray characterization of two octahydro-1H-4,6-epoxycyclopenta[c]pyridin-1-one derivatives that contain the four most abundant halogen atoms (Ha) in the structure with the aim of studying the formation of Ha···Ha halogen bonding interactions. The anisotropy of electron density at the heavier halogen atoms provokes the formation of multiple Ha···Ha contacts in the solid state. That is, the heavier Ha-atoms exhibit a region of positive electrostatic potential (σ-hole) along the C–Ha bond and a belt of negative electrostatic potential (σ-lumps) around the atoms. The halogen bonding assemblies in both compounds were analyzed using density functional theory (DFT) calculations, molecular electrostatic potential (MEP) surfaces, the quantum theory of “atom-in-molecules” (QTAIM), the noncovalent interaction plot (NCIplot), and the electron localization function (ELF).

Structural and biological characterization of a biomolecule: (3E)-3-(2, 4, 5-trimethoxyphenyl) methylidene) - 2, 3-dihydro-4H-1-benzopyran-4-one

The title compound, C19H18O5, has been synthesized using the Claisen-Schmidt condensation reaction from the mixture of 2,3 dihydro-4H-1-benzopyran-4-one and 2,4,5 trimethoxy benzaldehyde using ethanol as solvent. The crystal has been characterized for its 3 D structure and structural parameters were elucidated via the X-ray diffraction (XRD) method. The crystallographic parameters such as bond lengths, bond angles, and torsion angles were estimated and are comparable with the literature values. Hirshfeld surfaces namely dnorm, electrostatic potential, shape index, and curvedness were analyzed to visualize and to evaluate the weak intermolecular interactions, positive and negative potential regions, C-H…π, and π…π stacking interactions, respectively. The 2 D fingerprint plots for the whole and delineated interactions were also generated to estimate their contributions to the total Hirshfeld surface. The pairwise intermolecular interactions were calculated as the sum of four scaled energy components namely electrostatic (Eele), polarization (Epol), dispersion (Edis), and exchange-repulsion (Erep), and graphically represented as energy frameworks. The energy frameworks analysis reveals that the total stabilizing energy is highly influenced by dispersion (Edis) energy than the other components. The material has been screened for its cytotoxic effect on normal cell lines (VERO) and anticancer activity on breast cancer cell lines (MCF-7) and the material is found to be a potential candidate against cancer proliferation.

Probing IgG1 FC-Multimodal Nanoparticle Interactions: A Combined Nuclear Magnetic Resonance and Molecular Dynamics Simulations Approach.

In this study, NMR and molecular dynamics simulations were employed to study IgG1 FC binding to multimodal surfaces. Gold nanoparticles functionalized with two multimodal cation-exchange ligands (Capto and Nuvia) were synthesized and employed to carry out solution-phase NMR experiments with the FC. Experiments with perdeuterated 15N-labeled FC and the multimodal surfaces revealed micromolar residue-level binding affinities as compared to millimolar binding affinities with these ligands in free solution, likely due to cooperativity and avidity effects. The binding of FC with the Capto ligand nanoparticles was concentrated near an aliphatic cluster in the CH2/CH3 interface, which corresponded to a focused hydrophobic region. In contrast, binding with the Nuvia ligand nanoparticles was more diffuse and corresponded to a large contiguous positive electrostatic potential region on the side face of the FC. Results with lower-ligand-density nanoparticles indicated a decrease in binding affinity for both systems. For the Capto ligand system, several aliphatic residues on the FC that were important for binding to the higher-density surface did not interact with the lower-density nanoparticles. In contrast, no significant difference was observed in the interacting residues on the FC to the high- and low-ligand density Nuvia surfaces. The binding affinities of FC to both multimodal-functionalized nanoparticles decreased in the presence of salt due to the screening of multiple weak interactions of polar and positively charged residues. For the Capto ligand nanoparticle system, this resulted in an even more focused hydrophobic binding region in the interface of the CH2 and CH3 domains. Interestingly, for the Nuvia ligand nanoparticles, the presence of salt resulted in a large transition from a diffuse binding region to the same focused binding region determined for Capto nanoparticles at 150 mM salt. Molecular dynamics simulations corroborated the NMR results and provided important insights into the molecular basis of FC binding to these different multimodal systems containing clustered (observed at high-ligand densities) and nonclustered ligand surfaces. This combined biophysical and simulation approach provided significant insights into the interactions of FC with multimodal surfaces and sets the stage for future analyses with even more complex biotherapeutics.