CH CH2 Research Articles

Investigating the Influence of the Substrate Temperature and the Organic Precursor on the Mechanical Properties of Low‐Pressure Plasma Polymer Films

ABSTRACTThis work aims to investigate the influence of the substrate temperature on low‐pressure plasma polymerization processes. Emphasis is placed on the mechanical properties and growth mechanism of the plasma polymer films (PPFs). For this purpose, two precursors are considered, differing only by their unsaturation degree: 2‐propen‐1‐ol (CH2═CH–CH2–OH) and propan‐1‐ol (CH3–CH2–CH2–OH). Although propan‐1‐ol‐based PPFs behave like hard elastic solids, 2‐propen‐1‐ol‐based coatings evolve from a liquid film to an elastic solid on increasing the substrate temperature. This behavior is understood considering the evolution of the glass transition temperature of PPFs. The latter is correlated with the cross‐linking degree of the polymeric network governed by the energy density of bombarding ions on the growing film.

Antimicrobial activities of Alchornea cordifolia leaf extract on Candida albican and some selected Probiotics

The quest for novel and effective antimicrobial agents has become increasingly urgent because of the increasing threat of drug-resistant microbial pathogens. Alchornea cordifolia, a plant species widely used in traditional medicine, has been reported to possess antimicrobial properties. However, its antifungal activity and interactions with beneficial probiotic microorganisms remain poorly understood. This study aimed to investigate the antifungal efficacy of Alchornea cordifolia extracts and their bioactive components against Candida albicans and explore their interactions with probiotic microorganisms, Lactobacillus acidophilus and Sacchromyces bourdii, which are often used for control. By elucidating the antimicrobial potential and probiotic interactions of Alchornea cordifolia, this study aims to contribute to the development of innovative and sustainable solutions for the prevention and treatment of Candida albicans infections while also promoting a balanced microbiota. The crude extract was subjected to phytochemical screening. The bioactive components were isolated and purified via column chromatography and thin layer chromatography, whereas FTIR was used to analyse the functional groups present in the extract and isolated components. The extract and isolated components were further subjected to antimicrobial, minimum inhibitory concentration (MIC) and minimum fungicidal/bactericidal concentration (MFC/MBC) assays against C. albicans, S. bourdii and L. acidophilus via the agar diffusion and broth macrodilution technique. Phytochemical analysis revealed the presence of various bioactive components, including tannins, flavonoids, phenols, saponins, alkaloids, anthocyanins, cardiac glycosides, cyanogenic glycosides, oxalates, carotene and sterols. Four spots with Rf values between 0.73 and 0.75, 0.83 and 0.73, 0.87 and 0.98 and 0.32 and 0.23 assigned as components A, B, C and D, respectively, were isolated after elution with a gradient of solvents. The FTIR results of the crude extract revealed functional groups consistent with those of secondary metabolites, such as hydroxyl groups (O-H, peaks at 3812–3500 cm-1), amines (N–H stretching peaks at 3431 cm-1), alkenes (C-H stretching CH3 CH2, CH peaks at 3175–2800 cm-1), and C=C peaks at 1623 cm-1. These functional groups were identified during preliminary tests. The crude extract and components A, B, and C exhibited similar activities against Candida albicans, with inhibition zones ranging from 21 mm to 32 mm. Component C had the highest activity, with an inhibition zone of 32 mm. Component D showed moderate activity, with an inhibition zone of 26 mm. Antimicrobial activity against Sacromyces boulardii and Lactobacillus acidophilus varied among the components, with Component C showing the highest activity against Sacromyces boulardii. There was some selectivity for the pathogen rated as the crude extract ˃C ˃B = A ˃D. The crude extract and components A, B, and C had MICs of 100 µg/ml against Candida albicans. Component C had an MIC of 1000 µg/ml against Sacromyces boulardii. Component D had an MIC of 10 µg/ml against Candida albicans. The methanol crude extract and its components have shown promising antimicrobial activity against Candida albicans, making it a potential natural solution for candidiasis management. Further research will be crucial to unlock its full potential and explore its use in combination with probiotics. Keywords: Alchornea cordifolia, candidiasis, probiotics and antimicrobial

Human Primary Lens Epithelial Cultures on Basal Laminas Studied by Synchrotron-Based FTIR Microspectroscopy for Understanding Posterior Capsular Opacification.

Human primary lens epithelial cultures serve as an in vitro model for posterior capsular opacification (PCO) formation. PCO occurs when residual lens epithelial cells (LECs) migrate and proliferate after cataract surgery, differentiating into fibroblastic and lens fiber-like cells. This study aims to show and compare the bio-macromolecular profiles of primary LEC cultures and postoperative lens epithelia LECs on basal laminas (bls), while also analyzing bls and cultured LECs separately. Using synchrotron radiation-based Fourier transform infrared (SR-FTIR) (Bruker, Karlsruhe, Germany) microspectroscopy at the Spanish synchrotron light source ALBA, we observed that the SR-FTIR measurements were predominantly influenced by the strong collagen absorbance of the bls. Cultured LECs on bls showed a higher collagen contribution, indicated by higher vas CH3, CH2 and CH3 wagging and deformation, and the C-N stretching of collagen. In contrast, postoperative LECs on bls showed a higher cell contribution, indicated by the vsym CH2 peak and the ratio between vas CH2 and vas CH3 peaks. The primary difference revealed using SR-FTIR is the greater LEC contribution in spectra recorded from postoperative lens epithelia compared to cultured LECs on bls. IR spectra for bl, cultured LECs and postoperative lens epithelia could be valuable for future research.

Accurate measurement of sulfhydryls and TCEP-releasable sulfhydryls in the liquid phase of wine that contribute to ‘reductive’ aromas using LC-MS/MS

Volatile sulfur compounds (VSCs) are important aroma and flavour characters in food and beverage products. The identification and quantification of these extremely reactive and volatile compounds pose analytical challenges which demand selective and sensitive methods. In this study, a novel quantification method was developed to analyse sulfhydryls as well as the total pool of sulfhydryls which can be released after tris(2-carboxyethyl)phosphine (TCEP) addition from disulfides, polysulfides, metal-bound and other yet to be identified sources naturally present in wine. The majority of methods for VSC quantification analyse VSCs in wine headspace, whereas this method measures sulfhydryls and TCEP-releasable sulfhydryl species, which likely include free and metal-bound sulfhydryl forms, in the liquid phase of wine using UHPLC-MS/MS. Sulfhydryls were derivatised with N-(2-ferroceneethyl) maleimide (FEM), subsequently, followed by differential labelling of sulfhydryls released after TCEP addition with ferrocenecarboxylic acid-(2-maleimidoyl)ethylamide (FMEA). Analysis of commercial wines revealed the presence of hydrogen sulfide, methanethiol, ethanethiol, and 2-mercaptoethanol at aroma-active concentrations. Significant positive correlations were found between MeSH and CH3–S-R TCEP-releasable species, and significant positive correlations were found between EtSH and CH3–CH2–S-R TCEP-releasable species. This method provides important information on sulfhydryls, and may also provide insights into a wine's risk of developing ‘reductive’ faults post-bottling from latent sources.

High-Performance Li-Organic Batteries Based on Conjugated and Nonconjugated Schiff-Base Polymer Anode Materials.

In recent years, organic materials have been increasingly studied as anode materials in lithium-ion batteries (LIBs) due to their remarkable advantages, including abundant raw materials, low prices, diverse structures, and high theoretical capacity. In this paper, three types of aromatic Schiff-base polymer materials have been synthesized and examined as anode materials in LIBs. Among them, the polymer [C6H4N = CHC6H4CH=N]n (TTD-PDA) has a continuous conjugated backbone (label as conjugated polymer), while polymers [(CH2)2N=CHC6H4CH=N]n (TTD-EDA) and [C6H4N=CH(CH2)3CH=N]n (GA-PDA) have discontinuous conjugated back-bones (label as nonconjugated polymer). The organic anodes based on TTD-PDA, TTD-EDA, and GA-PDA for LIBs are discovered to represent high reversible specific capacities of 651, 492, and 416 mAh g-1 at a current density of 100 mA g-1 as well as satisfactory rate capabilities with high capacities of 210, 90, and 178 mAh g-1 and 105, 57, and 122 mAh g-1 at current densities of 2 and 10 A g-1, indicating that these Schiff-base polymers are all promising anode materials for LIBs, which broadens the design of organic anode materials with high specific capacity, superior rate performance, and stable cycling stability.

Exploiting Hydrogen Interaction of Drugs and Biodegradable Scaffolds Using Nanoparticles Loaded Nanofibers

AbstractThis study presents a detailed investigation of the structural and surface modifications of Fe3O4 nanoparticles (NPs). Fourier Transform Infrared (FTIR) spectroscopy was utilized to analyze the distinct characteristic peaks of Fe3O4 NPs and their subsequent modifications with stearic acid (ST) layers. The FTIR analysis revealed characteristic peaks at 580 cm−1, and 441 cm−1, corresponding to the Fe‐O stretching vibrations of the bulk Fe3O4 NPs. The successful loading of stearic acid onto the Fe3O4 NPs was confirmed by the appearance of new peaks at 1413 cm−1 and 2908 cm−1, indicative of the asymmetric CH2 stretch and CH3 umbrella vibration modes of stearic acid. UV‐Vis spectroscopy further corroborated the efficient loading of tetracycline and ibuprofen onto Fe3O4/DST nanoparticles, as evidenced by changes in absorption spectra. N2 adsorption‐desorption isotherms illustrated the presence of micro and meso pores on the surface of Fe3O4 NPs, with alterations in pore volume and diameter post‐surface modification and drug loading. Evaluation of magnetic properties indicated a reduction in saturation magnetization after surface modification and drug loading, attributed to changes in homogeneity and surface moments. Differential Reflectance Spectroscopy (DRS) and Raman spectroscopy elucidated distinctive peaks and shifts in spectra, confirming the composition and structural changes in drug‐loaded nanofibers.

Superfast Formation of C(sp2 )-N, C(sp2 )-P, and C(sp2 )-S Vinylic Bonds in Water Microdroplets.

We report examples of C(sp2 )-N, C(sp2 )-S, and C(sp2 )-P bond-forming transformations in water microdroplets at room temperature and atmospheric pressure using N2 as a nebulizing gas. When an aqueous solution of vinylic acid and amine is electrosprayed (+3 kV), the corresponding C(sp2 )-N product is formed in a single step, which was characterized using mass spectrometry (MS) and tandem mass spectrometry (MS2 ). The scope of this reaction was extended to other amines and other unsaturated acids, including acrylic (CH2 =CHCOOH) and crotonic (CH3 CH=CHCOOH) acids. We also found that thiols and phosphines are viable nucleophiles, and the corresponding C(sp2 )-S and C(sp2 )-P products are observed in positive ion mode using MS and MS2 .

Raman spectroscopy and scanning electron microscopy application for physical characterization of horsehairs

Horsehairs present several common characteristics in their chemical composition and molecular structure. The present study aims to analyze the physical characteristics of horsehairs belonging to different breeds. Morphological analysis of the horsehair fibers was performed using Scanning Electron Microscopy (SEM) and molecular structural characterization using the Raman Spectroscopy (RS) technique. Horse hairs were collected from three different horse groups (group A: mixed-breed; group B: Italian saddle; group C: thoroughbred). Each group was constituted of five horses with a mean body weight of 475 ± 25 kg, aged between 12 and 15 years old. SEM images showed differences in the surface layer (cuticula) and diameter size of horsehairs referred to different breeds. The investigation conducted through RS showed differences in the S – O band, located at 1044 cm−1, where cysteic acid is one of the amino acid constituents of α-keratin; in CH2 bending mode and CH stretching, located at ~1450 cm-1 and ~2900 cm-1, respectively. These differences could be attributed to genetic predisposition or metabolism; they could represent the real differentiation among the breeds, detectable by using RS.

Phase shift cavity ring down and FT-NIR spectra of C[sbnd]H vibrational transitions and band strengths of ethyl acetate

The vibrational overtone spectra (Δυ = 5, 6) of CH transitions of ethyl acetate (CH3COO–CH2CH3) have been obtained using the phase shift cavity ring down (PS-CRD) technique at 295 K. The CH stretch fundamental and overtone transitions (Δυ = 1- 4) have been obtained using a Fourier transform infrared and near infrared spectrophotometer. Local mode frequencies ωe and anharmonicities ωexe are reported for the CH (ip) (in plane), CH (op) (out of plane) bonds of the methyl group attached to the carbonyl (CO) side and for the methyl CH3 (primary) and methylene CH2 (secondary) CH bonds of the ethyl group bonded to the O atom. The study includes computer deconvolution of the total band at each level and a density functional theory (DFT) calculation of deuterated analogues of ethyl acetate to help with the assignment of all the non-equivalent CH bonds in the molecule. From the assigned Δυ = 6 peak wavenumber, isolated frequencies and CH bond lengths are obtained for the different CH bonds. Band strengths, oscillator strengths, and transition moments were obtained experimentally for all transitions. The importance of the assigned vibrational transitions and integrated intensities for future studies of laser and atmospheric vibrational overtone photochemistry is discussed.

Effect of the Nature of Both Cation and Anion Substitution on the Structural Symmetry of Li‐Rich 3d‐Metal Chalcogenide Electrodes

AbstractLi‐rich layered chalcogenides have recently led to better understanding of the anionic redox process and its associated high capacity while providing ways to overcome its practical limitations of voltage fade and irreversibility. This study reports on the feasibility of triggering anionic activity in Li2TiS3, through anionic substitution (Se for S) or cationic substitution (Fe for Ti). Herein, the chalcogenide chemical space is further explored to prepare mono‐substituted Li1.7Ti0.85Mn0.45Ch3 (Ch = S/Se) and doubly substituted cationic and anionic phases (Li1.7Ti0.85Fe0.45S3‐zSez) which crystallize either in the O3‐ or O1‐type structures depending upon substituents. All series show a bell‐shape capacity variation as function of the transition metal (TM) substitution degree with values up to 240 mAh g−1. For specific compositions, a structural O3 to O1 phase transition is observed upon Li removal, which is not reversible upon Li re‐insertion due to kinetic limitations and negatively affects long‐term cycling performance. Density functional theory (DFT) calculations confirm the O3/O1 relative stability along the different series and point subtle electronic differences in the TM‐doping, rationalizing the structural and electrochemical behaviors of these phases upon cycling. These findings provide further insights into the link between structural and electronic stability, which is of key importance for designing chalcogenide‐based anionic redox compounds.

Interfacial Electron Engineering of PdSn-NbN/C for Highly Efficient Cleavage of the C-C Bonds in Alkaline Ethanol Electrooxidation.

The splitting of the C-C bonds of ethanol remains a key issue to be addressed, despite tremendous efforts made over the past several decades. This study highlights the enhancement mechanism of inexpensive NbN-modified Pd1 Sn3 -NbN/C towards the C-C bonds cleavage for alkaline ethanol oxidation reaction (EOR). The optimal Pd1 Sn3 -NbN/C delivers a catalytic activity up to 43.5 times higher than that of commercial Pd/C and high carbonate selectivity (20.5%) toward alkaline EOR. Most impressively, the Pd1 Sn3 -NbN/C presents good durability even after 25 200 s of chronoamperometric testing. The enhanced catalytic performance is mainly due to the interfacial interaction between PdSn and NbN, demonstrated by multiple structural characterization results. In addition, in situ ATR-SEIRAS (Attenuated total reflection-surface enhanced infrared absorption spectroscopy) results suggest that NbN facilitates the C-C bonds cleavage towards the alkaline EOR, followed by the enhanced OH adsorption to promote the subsequent oxidation of C1 intermediates after doping Sn. DFT (density functional theory) calculations indicate that the activation barriers of the C-H bond cleavage in CH3 CH2 OH, CH3 CHOH, CH3 CHO, CH3 CO, CH2 CO, and the C-C bond cleavage in CH3 CO, CH2 CO, CHCO are evidently reduced and the removal of adsorbed CH3 CO and CO becomes easier on the PdSn-NbN/C catalyst surface.

Zero-Dimensional Sn-Based Enantiomeric Phase-Transition Materials with High-Tc and Dielectric Switching.

The combination of chirality and phase-transition materials has broad application prospects. Therefore, based on the quasi-spherical theory and the thought strategy of introducing chirality, we have successfully synthesized a pair of chiral enantiomeric ligands (R/S)-triethyl-(2-hydroxypropyl)ammonium iodide, which can be combined with a tin hexachloride anion to obtain a pair of new organic-inorganic hybrid enantiomeric high-temperature plastic phase-transition materials: (R/S)-[CH3 CH(OH)CH2 N(CH2 CH3 )3 ]2 SnCl6 (1-R/1-S), which have a high temperature phase transition of Tc =384 K, crystallize in the P21 chiral space group at room temperature, and have obvious CD signals. In addition, compounds 1-R and 1-S have a good low-loss dielectric switch and broadband gap. This work is conducive to the research into chiral high-temperature reversible plastic phase-transition materials, and promotes the development of multi-functional phase-transition materials.

Tunable Synthesis of Monofluoroalkenes and Gem-Difluoroalkenes via Solvent-Controlled Rhodium-Catalyzed Arylation of 1-Bromo-2,2-difluoroethylene.

Divergent synthesis of fluorine-containing scaffolds starting from a suite of raw materials is an intriguing topic. Herein, we report the solvent-controlled rhodium-catalyzed tunable arylation of 1-bromo-2,2-difluoroethylene. The selection of the reaction solvents provides switchable defluorinated or debrominated arylation from readily available feedstock resources (both arylboronic acids/esters and 1-bromo-2,2-difluoroethylene are commercially available). This switch is feasible because of the difference in coordination ability between the solvent (CH2 Cl2 or CH3 CN) and the rhodium center, resulting in different olefin insertion. This protocol allows the convenient synthesis of monofluoroalkenes and gem-difluoroalkenes, both of which are important scaffolds in the fields of medicine and materials. Moreover, this newly developed solvent-regulated reaction system can be applied to the site-selective dechlorinated arylation of trichloroethylene. Overall, this study provides a useful strategy for the divergent synthesis of fluorine-containing scaffolds and provides insight into the importance of solvent selection in catalytic reactions.

Comprehensive Study Addressing the Challenge of Efficient Electrocatalytic Biomass Upgrading of 5-(Hydroxymethyl)Furfural (HMF) with a CH3 NH2 Ionic Liquid on Metal-Embedded Mo2 B2 MBene Nanosheets.

Amine-containing derivatives are important intermediates in drug manufacturing; sustainable synthesis of amine compounds from green carbon-based biomass derivatives has attracted increasing attention, especially the reductive amination of biomass molecules via electrochemical upgrading. To achieve efficient reductive amination of 5-(hydroxymethyl)furfural (HMF) via electrocatalytic biomass upgrading, this work proposes a new HMF biomass upgrading strategy based on metal supported on Mo2 B2 MBene nanosheets using a density functional theory comprehensive study. HMF and methylamine (CH3 CH2 ) can be reduced to 5-(hydroxymethyl) aldiminefurfural (HMMAMF) via electrocatalytic biomass upgrading, which is identified as a promising technology to produce pharmaceutical intermediates. Based on the proposed reaction mechanisms of HMF reductive amination, this work performs a systematic study of HMF amination to HMMAMF using an atomic model simulation method. This study aims to design a high-efficiency catalyst based on Mo2 B2 @TM nanosheets via the reductive amination of 5-HMF and provide insights into the intrinsic relation between thermochemical and material electronic properties and the role of dopant metals. This work establishes the Gibbs free energy profiles of each reaction HMF Biomass Upgrading on Mo2 B2 systems and obtained the limiting potentials of the rate-determining step, which included the kinetic stability of dopants, HMF adsorbability, and the catalytic activity and selectivity of the hydrogen evolution reaction or surface oxidation. Furthermore, charge transfer, d-band center (εd ), and material property (φ) descriptors are applied to establish a linear correlation to determine promising candidate catalysts for reductive amination of HMF. The candidates Mo2 B2 @Cr, Mo2 B2 @Zr, Mo2 B2 @Nb, Mo2 B2 @Ru, Mo2 B2 @Rh, and Mo2 B2 @Os are suitable high-efficiency catalysts for HMF amination. This work may contribute to the experimental application of biomass upgrading catalysts for biomass energy and guide the future development of biomass conversion strategies and utilization.

Reassessing the Composition of Hybrid Orbitals in Contemporary VB Calculations.

Large variations in the ratios between the p and s components of individual hybrid orbitals that have been observed in contemporary ab initio VB calculations are reassessed, and links are established to specific energy terms that drive bond formation. It is demonstrated that the ratios between the p and s components for individual hybrid orbitals are not indicative of the overall hybridization status of the relevant atom, which exhibits only relatively small variations with the level of theory, irrespective of whether or not non-dynamical and dynamical electron correlation effects are accounted for. An alternative orbital representation that turns out to be far more consistent with the overall hybridization of the relevant atom is examined. The chosen test cases, which can be compared with the classical sp3, sp2, and sp hybridization models for a central carbon atom, are CH4 (Td), trigonal CH3 (D3h), and triplet CH2 distorted from its ground state geometry so as to be linear (D∞h).

Anion redox as a means to derive layered manganese oxychalcogenides with exotic intergrowth structures

Topochemistry enables step-by-step conversions of solid-state materials often leading to metastable structures that retain initial structural motifs. Recent advances in this field revealed many examples where relatively bulky anionic constituents were actively involved in redox reactions during (de)intercalation processes. Such reactions are often accompanied by anion-anion bond formation, which heralds possibilities to design novel structure types disparate from known precursors, in a controlled manner. Here we present the multistep conversion of layered oxychalcogenides Sr2MnO2Cu1.5Ch2 (Ch = S, Se) into Cu-deintercalated phases where antifluorite type [Cu1.5Ch2]2.5- slabs collapsed into two-dimensional arrays of chalcogen dimers. The collapse of the chalcogenide layers on deintercalation led to various stacking types of Sr2MnO2Ch2 slabs, which formed polychalcogenide structures unattainable by conventional high-temperature syntheses. Anion-redox topochemistry is demonstrated to be of interest not only for electrochemical applications but also as a means to design complex layered architectures.

Lysozyme Interaction with Phospholipid Nanodroplets Probed by Sum Frequency Scattering Vibrational Spectroscopy.

When a nanoparticle (NP) is introduced into a biological environment, its identity and interactions are immediately attributed to the dense layer of proteins that quickly covers the particle. The formation of this layer, dubbed the protein corona, is in general a combination of proteins interacting with the surface of the NP and a contest between other proteins for binding sites either at the surface of the NP or upon the dense layer. Despite the importance for surface engineering and drug development, the molecular mechanisms and structure behind interfacial biomolecule action have largely remained elusive. We use ultrafast sum frequency scattering (SFS) spectroscopy to determine the structure and the mode of action by which these biomolecules interact with and manipulate interfaces. The majority of work in the field of sum frequency generation has been done on flat model interfaces. This limits some important membrane properties such as membrane fluidity and dimensionality─important factors in biomolecule-membrane interactions. To move toward three-dimensional (3D) nanoscopic interfaces, we utilize SFS spectroscopy to interrogate the surface of 3D lipid monolayers, which can be used as a model lipid-based nanocarrier system. In this study, we have utilized SFS spectroscopy to follow the action of lysozyme. SFS spectra in the amide I region suggest that there is lysozyme at the interface and that the lysozyme induces an increased lipid monolayer order. The binding of lysozyme with the NP is demonstrated by an increase in acyl chain order determined by the ratio of the CH3 symmetric and CH2 symmetric peak amplitudes. Furthermore, the lipid headgroup orientation s-PO2- change strongly supports lysozyme insertion into the lipid layer causing lipid disruption and reorientation. Altogether, with SFS, we have made a huge stride toward understanding the binding and structure change of proteins within the protein corona.

Gas-phase formation of Grignard-type organolanthanide (III) ions RLnCl3 - : The influences of lanthanide center and hydrocarbyl group.

Compared with organomagnesium compounds (Grignard reagents), the Grignard-type organolanthanides (III) exhibit several utilizable differences in reactivity. However, the fundamental understanding of Grignard-type organolanthanides (III) is still in its infancy. Decarboxylation of metal carboxylate ions is an effective method to obtain organometallic ions that are well suited for gas-phase investigation using electrospray ionization (ESI) mass spectrometry in combination with density functional theory (DFT) calculations. The (RCO2 )LnCl3 - (R = CH3 , Ln = La-Lu except Pm; Ln = La, R = CH3 CH2 , CH2 CH, HCC, C6 H5 , and C6 H11 ) precursor ions were produced in the gas phase via ESI of LnCl3 and RCO2 H or RCO2 Na mixtures in methanol. Collision-induced dissociation (CID) was employed to examine whether the Grignard-type organolanthanide (III) ions RLnCl3 - can be obtained via decarboxylation of lanthanide chloride carboxylate ions (RCO2 )LnCl3 - . DFT calculations can be used to determine the influences of lanthanide center and hydrocarbyl group on the formation of RLnCl3 - . When R = CH3 , CID of (CH3 CO2 )LnCl3 - (Ln = La-Lu except Pm) yielded decarboxylation products (CH3 )LnCl3 - and reduction products LnCl3 ·- with a variation in the relative intensity ratio of (CH3 )LnCl3 - /LnCl3 ·- . The trend is as follows: (CH3 )EuCl3 - /EuCl3 ·- < (CH3 )YbCl3 - /YbCl3 ·- ≈ (CH3 )SmCl3 - /SmCl3 ·- < other (CH3 )LnCl3 - /LnCl3 ·- , which complies with the trend of Ln (III)/Ln (II) reduction potentials in general. When Ln = La and hydrocarbyl groups were varied as CH3 CH2 , CH2 CH, HCC, C6 H5 , and C6 H11 , the fragmentation behaviors of these (RCO2 )LaCl3 - precursor ions were diverse. Except for (C6 H11 CO2 )LaCl3 - , the four remaining (RCO2 )LaCl3 - (R = CH3 CH2 , CH2 CH, HCC, and C6 H5 ) ions all underwent decarboxylation to yield RLaCl3 - . (CH2 CH)LaCl3 - and especially (CH3 CH2 )LaCl3 - are prone to undergo β-hydride transfer to form LaHCl3 - , whereas (HCC)LaCl3 - and (C6 H5 )LaCl3 - are not. A minor reduction product, LaCl3 ·- , was formed via C6 H5 radical loss of (C6 H5 )LaCl3 - . The relative intensities of RLaCl3 - compared to (RCO2 )LaCl3 - decrease as follows: HCC > CH2 CH > C6 H5 > CH3 > CH3 CH2 >> C6 H11 (not visible). A series of Grignard-type organolanthanide (III) ions RLnCl3 - (R = CH3 , Ln = La-Lu except Pm; Ln = La, R = CH3 CH2 , CH2 CH, HCC, and C6 H5 ) were produced from (RCO2 )LnCl3 - via CO2 loss, whereas (C6 H11 )LaCl3 - did not. The experimental and theoretical results suggest that the reduction potentials of Ln (III)/Ln (II) couples as well as the bulkiness and hybridization of hydrocarbyl groups play important roles in promoting or limiting the formation of RLnCl3 - via decarboxylation of (RCO2 )LnCl3 - .

An Efficient Method to Generate Dense Amorphous Structures for Molecular Simulation of Vinyl Polymers

AbstractAn efficient technique to construct dense amorphous polymers at the bulk density is illustrated for two vinyl polymers, i.e., PVX, –[CH2–CH(X)]–. Bulk amorphous polypropylene (PP) and polystyrene (PS) structures are generated starting from coarse‐graining polymer chains and are mapped onto the second nearest neighbor diamond (2nnd) lattice. PVX are represented by the rotational isomeric state (RIS) model and non‐bonded interactions are treated by the Lennard–Jones (LJ) potential function. Lattice Monte Carlo (MC) simulation is utilized to equilibrate coarse‐grained (C) PVX and the fully atomistic models can be recovered by the reverse‐mapping procedure to restore the missing atoms. After geometry optimization, chain and material properties of bulk PVX structure are computed to validate the atomistic models including conformational characteristics, Hildebrand solubility parameter, pair correlation function, and scattering structure factor.

Evaluation of preferred binding regions on ubiquitin and IgG1 FC for interacting with multimodal cation exchange resins using DEPC labeling/mass spectrometry.

There is significant interest in identifying the preferred binding domains of biological products to various chromatographic materials. In this work, we develop a biophysical technique that uses diethyl pyrocarbonate (DEPC) based covalent labeling in concert with enzymatic digestion and mass spectrometry to identify the binding patches for proteins bound to commercially available multimodal (MM) cation exchange chromatography resins. The technique compares the changes in covalent labeling of the protein in solution and in the bound state and uses the differences in this labeling to identify residues that are sterically shielded upon resin binding and, therefore, potentially involved in the resin binding process. Importantly, this approach enables the labeling of many amino acids and can be carried out over a pH range of 5.5-7.5, thus enabling the protein surface mapping at conditions of interest in MM cation exchange systems. The protocol is first developed using the model protein ubiquitin and the results indicate that lysine residues located on the front face of the protein show dramatic changes in DEPC labeling while residues present on other regions have minimal or no reductions. This indicates that the front face of ubiquitin is likely involved in resin binding. In addition, surface property maps indicate that the hypothesized front face binding region consists of overlapping positively charged and hydrophobic patches. The technique is then employed with an IgG1 FC and the results indicate that residues on the CH 2-CH 3 interface and the hinge are significantly sterically shielded upon binding to the resin. Further, these regions are again associated with significant overlap of positively charged and hydrophobic patches. On the other hand, while, residues on the CH 2 and the front face of the IgG1 FC also exhibited some changes in DEPC labeling upon binding, these regions have less distinct charged and hydrophobic patches. Importantly, the hypothesized binding patches identified for both ubiquitin and FC using this approach are shown to be consistent with previously reported NMR studies. In contrast to NMR, this new approach enables the identification of preferred binding regions without the need for isotopically labeled proteins or chemical shift assignments. The technique developed in this work sets the stage for the evaluation of the binding domains of a wide range of biological products to chromatographic surfaces, with important implications for designing biomolecules with improved biomanufacturability properties.