Intrinsic Chemical Reactivity Research Articles

Effect of composition of multicomponent supports on properties of supported Nickel catalysts

Ni catalysts supported on combinations of alumina, magnesia, zirconia with rare earth supports are studied for the steam reforming of ethanol (ESR). The composition of the supports is systematically varied to identify the role of individual components and their contribution when they are combined. Supports containing magnesia or zirconia show contrasting behavior of acidity, XRD crystallite size of NiO, reducibility, dispersion of Ni(0), OSC, coking and metals sintering characteristics. Catalyst activity and deactivation are strongly influenced due to these differences. HRTEM indicates the redispersion of Ni(0) during reduction of NiO on catalysts containing magnesia. Magnesia and alumina-magnesia based catalysts show hindered reduction of nickel and highest intrinsic activity (H2 yields). But sintering of Ni is their nemesis. Moderate interaction of Ni with zirconia-based supports (H2-TPR) lends sintering stability in ESR. Quaternary Alumina-Magnesia-Zirconia catalysts imbibe advantages of individual components and are overall best with fair H2 yield, good stability and regenerability. Long duration (80 hours) performance tests give holistic results because they encompass multiple factors influencing deactivation. Intrinsic chemical reactivity (as opposed to) active metal dispersion is important while comparing the activity of catalysts with different compositions. Degree of reducibility of nickel is an important consideration while measuring metal dispersion by chemisorption. Metal reducibility by H2-TPR, dispersion measurement by chemisorption and particle size determination by HRTEM are used as complementary techniques for rationalizing results of metal dispersion measurement.

Harnessing the Intrinsic Chemical Reactivity of the Mycotoxin Patulin for Immunosensing.

Mycotoxins are globally pervasive contaminants that threaten food safety worldwide. Regulatory authorities have established maximum permissible levels for certain mycotoxins, and their presence is routinely monitored throughout the food chain to ensure the provision of healthy food and safe feed for humans and animals. While immunoanalytical methods are essential for mycotoxin screening, monoclonal antibodies for the detection of patulin are notably absent. Moreover, leading immunodiagnostic companies currently do not offer rapid tests for patulin in their product portfolios. This deficiency in mycotoxin testing is primarily due to the electrophilic reactivity of patulin. In this study, we exploit this reactivity to develop an innovative strategy that targets the stable adduct formed by the reaction of patulin with aryl-1,2-dithiolates, rather than analyzing the mycotoxin itself. Based on this previously unknown reaction, we present the first collection of monoclonal antibodies, enabling the long-sought goal of sensitive, simple, and user-friendly immunosensing of patulin.

Understanding the chemical reactivity and biological properties of patellamides using theoretical and computational methods

Patellamides are cyclic peptides produced by marine cyanobacteria with potential pharmaceutical properties. Chemical Reactivity Theory, specifically Conceptual DFT-based Computational Peptidology (CDFT-CP), can predict the electronic and structural properties of peptides, as well as their intrinsic chemical reactivity features and aid in designing new peptide-based drugs. Computational ADMET can complement these predictions by evaluating how the drug will behave in the body. This study reports on the results of a CDFT-CP and Computational Pharmacokinetics analysis of Patellamides A–G, including their predicted chemical reactivity descriptors, biological targets, bioactivity radars and ADMET parameters. These tools provide a powerful approach for understanding peptide properties and developing new drugs.

Alkynyl-Enrichable Carboxyl-Selective Crosslinkers to Increase the Crosslinking Coverage for Deciphering Protein Structures.

The coverage of chemical crosslinking coupled with mass spectrometry (CXMS) is of great importance to determine its ability for deciphering protein structures. At present, N-hydroxysuccinimidyl (NHS) ester-based crosslinkers targeting lysines have been predominantly used in CXMS. However, they are not always effective for some proteins with few lysines. Other amino acid residues such as carboxyl could be crosslinked to complement lysines and improve the crosslinking coverage of CXMS, but the low intrinsic chemical reactivity of carboxyl compromises the application of carboxyl-selective crosslinkers for complex samples. To enhance the crosslinking efficiency targeting acidic residues and realize in-depth crosslinking analysis of complex samples, we developed three new alkynyl-enrichable carboxyl-selective crosslinkers with different reactive groups such as hydrazide, amino, and aminooxy. The crosslinking efficiencies of the three crosslinkers were systematically evaluated, giving the best reactivity of the amino-functionalized crosslinker BAP. Furthermore, BAP was extended to the crosslinking analysis of Escherichia coli lysate in combination with efficient crosslink enrichment. A total of 1291 D/E-D/E crosslinks involved in 392 proteins were identified under a false discovery rate (FDR) of ≤1%. Obvious structural complementarity of BAP was exhibited to the lysine-targeting crosslinker, facilitating the capability of CXMS for protein structure elucidation. To the best of our knowledge, this was the first time for the carboxyl-selective crosslinker to achieve proteome-wide crosslinking analysis of the whole cell lysate. Collectively, we believe that this work not only expands on a promising toolkit of CXMS targeting acidic residues but also provides a valuable guideline to advance the performance of carboxyl-selective crosslinkers.

Covalent Chemical Tools for Profiling Post-Translational Modifications.

Nature increases the functional diversity of the proteome through posttranslational modifications (PTMs); a process that involves the proteolytic processing or catalytic attachment of diverse functional groups onto proteins. These modifications modulate a host of biological activities and responses. Consequently, anomalous PTMs often correlate to a host of diseases, hence there is a need to detect these transformations, both qualitatively and quantitatively. One technique that has gained traction is the use of robust chemical strategies to label different PTMs. By utilizing the intrinsic chemical reactivity of the different chemical groups on the target amino acid residues, this strategy can facilitate the delineation of the overarching and inclusionary roles of these different modifications. Herein, we will discuss the current state of the art in post-translational modification analysis, with a direct focus on covalent chemical methods used for detecting them.

Click Bioconjugation: Modifying Proteins Using Click-Like Chemistry.

Bioconjugation deals with the chemical modification of proteins. The reactions used exploit either the intrinsic chemical reactivity of the biomolecule or introduce functionalities that can then be subsequently reacted without interfering with other functional groups of the biological entity. Perfectly selective, high yielding chemical transformations are needed that can be run in aqueous environment under mild pH conditions. Requirements that have an obvious overlap with the definition of click chemistry. This review shows a selection of successfully applied click-type reactions in bioconjugation as well as some recent developments to broaden the chemical toolbox to meet the challenge of selective, bioorthogonal modification of biomolecules.

Mechanisms and Kinetics Studies of Butylated Hydroxytoluene Degradation to Isobutene.

2,6-Di-tert-butyl-hydroxytotulene (BHT) is a widely used antioxidant in various fields. In this study, we explored comprehensively the mechanisms and kinetics of BHT degradation to produce isobutene using the density functional theory method. Furthermore, the intrinsic chemical reactivity of BHT was investigated using the electrostatic potential, average local ionization energy, and Fukui function, and the most likely reaction site with OH radical was predicted. Two initiation pathways of BHT with OH radicals were reported. The OH addition pathways at the C2 site of BHT was found more likely to occur than the pathways of H abstracts from the t-butyl group due to the lower energy barrier. Rate constants of two initiation pathways were calculated by transition state theory, and they were promoted by the temperature rise. Mayer bond order and localized molecular orbitals analysis were conducted to reveal the variation of the chemical bonds in the reaction process. The tertiary butyl radical that had been generated in the OH-addition reaction was more likely to generate isobutene with the participation of oxygen. Overall, this research could help to reveal the transformation mechanism of isobutene produced by BHT degradation.

Experimental and Molecular Simulation Studies of Huadian Oil Shale Kerogen.

Microscopic details on the intrinsic chemical reactivity of Huadian oil shale kerogen associated with electron properties of kerogen were investigated by the combination of experimental analyses and molecular simulations. Multimolecular structure models of kerogen with different densities were constructed for examining the accuracy of the proposed kerogen model. Results revealed that the simulated density of the kerogen model is in good agreement with the experimental value. Evaluation of the kerogen model revealed that the energy optimization process is mainly related to the change in the bond angle caused by atom displacement. According to the results from the Hirshfeld analysis of atomic charges, the S atoms in thiophene and S=O structures exhibit positive charges. By contrast, the concentration of electrons on the S atom led to the electronegativity of the sulfhydryl group. To investigate the distribution characteristics of electrons in kerogen, the molecular electrostatic potential (MEP) of a complete kerogen molecule was calculated. Notably, this is the first report of an MEP diagram of the kerogen model that can provide valuable information on the determination of electrophilic or nucleophilic reaction sites for kerogen.

Intrinsic chemical reactivity of activated human complement component C3: A historical glimpse into research during 1979–1980 on the covalent binding properties of C3, C4 and alpha-2 macroglobulin

A new type of intrinsic activity was revealed in the complement protein C3 during investigations of nucleophilic complement inhibitors. Nascent C3b molecules produced by cleavage-activation of C3 have highly reactive acyl groups which form short-lived sites for covalent binding to biological materials. Alpha-2 macroglobulin and C4 may utilise similar “autoligation” mechanisms.

Measuring Electronic Structure of Multiply Charged Anions to Understand Their Chemistry: A Case Study on Gaseous Polyhedral closo-Borate Dianions.

Research on multiply charged anions (MCAs) in the gas phase has been intensively performed during the past decades, mainly to understand fundamental molecular physics phenomena, for example, intramolecular Coulomb repulsion and existence of the repulsive Coulomb barrier. However, the relevance of these investigations with respect to understanding MCAs' chemistry appears often vague. Here, we discuss how insights into the electronic structure obtained from negative ion photoelectron spectroscopy (NIPES) combined with theoretical calculations and collision-induced dissociation can provide a fundamental understanding of the intrinsic chemical reactivity of MCAs and their fragments. This is exemplified in our studies on polyhedral closo-borate dianions [BnXn]2- (n = 6, 10, 11, 12; X = H, F-I, CN) and their fragment ions. For example, the rational design of closo-borate dianions with specific electronic properties is described, which leads to generating highly reactive fragments. Depending on the dianionic precursor, these fragments are tuned to either bind noble gases effectively or activate small molecules like CO and N2. The intrinsic electronic properties of closo-borate dianions are further compared to their electrochemistry in solutions, revealing solvent effects on the redox potentials. Neutral host molecules such as cyclodextrins are found to bind strongly to [BnXn]2-, and gas phase NIPES provides insights into the intrinsic host-guest interactions. Finally, outlooks including the direct NIPES of molecular fragment ions that cannot be generated in the condensed phase and their utilization in preparative mass spectrometry are discussed.

Classification and Milling Increase Fly Ash Pozzolanic Reactivity

Upcycling and reclaiming of low quality or stored coal combustion fly ashes could enable to tap into a voluminous resource of supplementary cementitious materials (SCMs) for low-carbon blended cements. Low reactivity fly ashes are usually either too crystalline or too coarse. Beneficiation treatments for coarse fly ashes comprise size classification or milling processes to extract or produce fine size fractions of higher pozzolanic reactivity. This article compares the effect of size classification and milling treatments on the reactivity of a siliceous fly ash (FA). The intrinsic chemical reactivity is assessed using the R3 heat release test method. The results showed significant increases of 57 and 40% for fine classified and milled fly ash compared to the initial fly ash, respectively. In addition heat release and portlandite consumption were measured for blended cements with 30 wt.% Portland cement replacement by the fly ashes. Both test results are combined to calculate the degree of reaction of the fly ashes over time in blended cement. The results demonstrate a strong effect of particle size on fly ash reactivity and degree of reaction. It is shown that increasing the inherent reactivity of fly ashes is an effective way of both accelerating compressive strength gain and enhancing late age strength with fine classified fly ashes reaching equivalent strength as neat Portland cement by 28 days and attaining a strength activity index of 137% by 90 days.

Highlights on Steroidal Arylidene Derivatives as a Source of Pharmacologically Active Compounds: A Review.

Steroids constitute a unique class of chemical compounds, playing an important role in physiopathological processes, and have high pharmacological interest. Additionally, steroids have been associated with a relatively low toxicity and high bioavailability. Nowadays, multiple steroidal derivatives are clinically available for the treatment of numerous diseases. Moreover, different structural modifications on their skeleton have been explored, aiming to develop compounds with new and improved pharmacological properties. Thus, steroidal arylidene derivatives emerged as a relevant example of these modifications. This family of compounds has been mainly described as 17β-hydroxysteroid dehydrogenase type 1 and aromatase inhibitors, as well as neuroprotective and anticancer agents. Besides, due to their straightforward preparation and intrinsic chemical reactivity, steroidal arylidene derivatives are important synthetic intermediates for the preparation of other compounds, particularly bearing heterocyclic systems. In fact, starting from arylidenesteroids, it was possible to develop bioactive steroidal pyrazolines, pyrazoles, pyrimidines, pyridines, spiro-pyrrolidines, amongst others. Most of these products have also been studied as anti-inflammatory and anticancer agents, as well as 5α-reductase and aromatase inhibitors. This work aims to provide a comprehensive overview of steroidal arylidene derivatives described in the literature, highlighting their bioactivities and importance as synthetic intermediates for other pharmacologically active compounds.

Chemical Reactivities of Two Widely Used Ruthenium-Based CO-Releasing Molecules with a Range of Biologically Important Reagents and Molecules.

Ruthenium-based CO-releasing molecules (CO-RMs), CORM-2 and CORM-3, have been widely used as surrogates of CO for studying its biological effects in vitro and in vivo with much success. However, several previous solution-phase and in vitro studies have revealed the ability of such CO-RMs to chemically modify proteins and reduce aromatic nitro groups due to their intrinsic chemical reactivity under certain conditions. In our own work of studying the cytoprotective effects of CO donors, we were in need of assessing chemical factors that could impact the interpretation of results from CO donors including CORM-2,3 in various in vitro assays. For this, we examined the effects of CORM-2,3 toward representative reagents commonly used in various bioassays including resazurin, tetrazolium salts, nitrites, and azide-based H2S probes. We have also examined the effect of CORM-2,3 on glutathione disulfide (GSSG), which is a very important redox regulator. Our studies show the ability of these CO-RMs to induce a number of chemical and/or spectroscopic changes for several commonly used biological reagents under near-physiological conditions. These reactions/spectroscopic changes cannot be duplicated with CO-deleted CO-RMs (iCORMs), which are often used as negative controls. Furthermore, both CORM-2 and -3 are capable of consuming and reducing GSSG in solution. We hope that the results described will help in the future design of control experiments using Ru-based CO-RMs.

New information of dopaminergic agents based on quantum chemistry calculations

Dopamine is an important neurotransmitter that plays a key role in a wide range of both locomotive and cognitive functions in humans. Disturbances on the dopaminergic system cause, among others, psychosis, Parkinson’s disease and Huntington’s disease. Antipsychotics are drugs that interact primarily with the dopamine receptors and are thus important for the control of psychosis and related disorders. These drugs function as agonists or antagonists and are classified as such in the literature. However, there is still much to learn about the underlying mechanism of action of these drugs. The goal of this investigation is to analyze the intrinsic chemical reactivity, more specifically, the electron donor–acceptor capacity of 217 molecules used as dopaminergic substances, particularly focusing on drugs used to treat psychosis. We analyzed 86 molecules categorized as agonists and 131 molecules classified as antagonists, applying Density Functional Theory calculations. Results show that most of the agonists are electron donors, as is dopamine, whereas most of the antagonists are electron acceptors. Therefore, a new characterization based on the electron transfer capacity is proposed in this study. This new classification can guide the clinical decision-making process based on the physiopathological knowledge of the dopaminergic diseases.

Theoretical insight into the hydrogenolysis mechanism of lignin dimer compounds based on experiments

Deep insight of reaction mechanism in lignin model compounds is helpful to achieve the directed depolymerization of lignin or biomass to chemicals or fuels. In this study, the density functional theory (DFT) calculation was employed to investigate the cleavage mechanism of the C–O bonds in lignin dimers. Additionally, the intrinsic chemical reactivity of molecular in term of the Fukui function was applied to predict the most probable sites which react with hydrogen free radicals (H·). It was found that the O atoms in lignin dimers are the most reaction site involving H· because of the large f (0). By this method, the most rational path from a series of reaction paths was screen out. Apart from the Fukui function, the average local ionization energy (ALIE) was analyzed to prove the reliability of Fukui function. The kinetic analysis of the reaction path was performed to further understand the impact of temperature on the reaction rate constant (KTST). It is observed that benzyl phenyl ether (BPE) with higher KTST could be easily cleaved because of the relatively low energy barrier.

Nanofluid-infused slippery surface: Bioinspired coating on Zn with high corrosion inhibition performance

Zn coating is widely used for protecting building construction surfaces exposed to atmospheric conditions. Due to the intrinsic chemical reactivity of Zn, it can be corroded by adventitious environmentally present corrosive species. Finding an effective protecting approach is critical in order to extend the life of a zinc coating and the substrate metal. In this work, using a facile salt spraying method, a porous matrix is formed on a Zn surface. After modification with dodecanethiol, the as-prepared porous matrix exhibits superhydrophobicity with a large water contact angle (WCA) of 158°. An upgraded bio-inspired slippery surface with high water-repellency is achieved by filling the nanofluid (NF) composed by nanoscale Fe3O4 and oleic acid into the pores on Zn (NF Zn). Surprisingly, this coating exhibits a sustainable anti-corrosion capability. The characteristic impedance of NF Zn coating increases 6 orders of magnitude in 3.5 wt% and 7.0 wt% NaCl aqueous solution, and the corrosion current density (Icorr) decreases by 4 and 5 orders of magnitude, respectively. After the salt spray test for 21 days, it still has a good protection effect on metallic zinc. In an acidic environment, the characteristic impedance of NF Zn increases 5 orders of magnitude, and Icorr decreases 4 orders of magnitude than that of bare Zn, performing a good anti-corrosion effect. After immersion for 16 days, the low-frequency impedance and current density of NF Zn increase and decrease by 5 and 6 orders of magnitude, respectively. NF can be used as an anti-corrosion coating to protect Zn in different environments.

Hierarchical Surface Architecture of Hemodialysis Membranes for Eliminating Homocysteine Based on the Multifunctional Role of Pyridoxal 5'-phosphate.

Patients with end-stage renal disease are prone to developing a complication of hyperhomocysteinemia, manifesting as an elevation of the homocysteine (Hcy) concentration in human plasma. However, Hcy as a protein-bound toxin is barely removed by conventional hemodialysis membranes. Here, we report a novel hemodialysis membrane by preparing a bioactive coating of pyridoxal 5'-phosphate (PLP) and adding biocompatible hyperbranched polyglycerol (HPG) brushes to achieve Hcy removal. The dip-applied PLP coating, a coenzyme with a role in Hcy metabolism, dramatically promoted a decrease in the Hcy concentration in human plasma. Moreover, the aldehyde group of PLP had an intrinsic chemical reactivity toward the terminal amino group to immobilize the HPG brushes on the hemodialysis membrane surface. The hierarchical PLP-HPG layer-functionalized membranes had a high efficacy for eliminating Hcy, with a concentration from the initial stage of 150 μmol/L reduced to a nearly normal level of 20 μmol/L in simulated dialysis. By analyzing the impact of HPG brushes with various chain lengths, we found that HPG brushes with a medium length enabled the PLP coating with the bioactive function of Hcy conversion to additionally protect Hcy-attacked target cells by providing excellent hydrophilicity and a dense enough chain volume overlap of the hyperbranched architecture. Simultaneously, the densely packed HPG brushes generated a maximal steric and hydration barrier that significantly improved biofouling resistance against blood proteins. The optimally functionalized membranes showed a clearance of 83.1% urea and 49.6% lysozyme and a rejection of 96.0% bovine serum albumin. The diversely functionalized PLP-HPG layers demonstrate a potential route for a more integrated hemodialysis membrane that can cope with the urgent issue of hyperhomocysteinemia in clinical hemodialysis therapy.

Theoretical description of the electronic properties and intrinsic chemical reactivity of organic compounds derived from 1,3-Benzoxazole

The electronic and intrinsic chemical reactivity properties of four single ring chain structure organic compounds derived from 1,3-Benzoxazole, based on to mono- and bi-substitution of acceptor and donor fragments of electrons. This theoretical study was motivated by the need to inquire specifically about the effect of electric charge transfer individual and simultaneous of the substitutes into one of the parent compound phenyl rings. The amino and nitro groups were used as fragments, respectively. The results found from this study are important because it provides key aspects to understand mechanisms for the design of novel structures for the development of new materials with appropriate properties and explore their potential use as biomarkers, active media for tunable lasers, or active layers for solar cells and suggest their possible use for these applications based on 27-Phenyl-30-Oxazol-2-Phenyl-1,3-Benzoxazole from the comparative study of their electronic and chemical reactivity properties of 27-Phenyl-30-Oxazol-2-Phenyl-1,3-Benzoxazole and compounds derived. The Gaussian 03 software suite was used as a computer calculation tool, while the calculations were computed by using the hybrid functional that combines Becke’s three-parameter exchange functional with Lee Yang Parr’s correlation functional.

Intrinsic chemical reactivity of solid-electrolyte interphase components in silicon–lithium alloy anode batteries probed by FTIR spectroscopy

The chemical reactivity of silicon surface species with LiPF6/carbonate electrolyte are detailed via FTIR spectroscopy and verified by MD/DFPD simulations.

An Exceptionally Stable and Scalable Sugar–Polyolefin Frank–Kasper A15 Phase

Abstract“One‐component” soft material Frank–Kasper (FK) phases are an intriguing structural form of matter that possess periodically ordered structures arising from the self‐reconfiguration and close packing of an initial assembly of identical “deformable” spheres into two or more size‐ or shape‐distinct sets of particles. Significant challenges that must still be addressed to advance the field of soft matter FK phases further, however, include their rare and unpredictable occurrence, uncertain mechanisms of solid‐state assembly, and low thermodynamic stability. Here we show that a readily‐accessible sugar–polyolefin conjugate quantitatively produces an exceptionally stable solid‐state FK A15 phase through a rapid and irreversible thermotropic order–order transition, which contrary to other prevailing proposed mechanisms, does not require mass transfer between particles or large structural reorganization in the bulk to establish unit cell non‐equivalency. Our results provide the basis for a realistic strategy for obtaining practical and scalable quantities of a diverse range of sugar–polyolefin FK A15 phases with unique intrinsic physical properties and chemical reactivities not previously seen in such systems.