Reaction Mechanism Of Hydrolysis Research Articles

Reaction Mechanism of Actin ATP Hydrolysis Studied by QM/MM Calculations

Reaction Mechanism of Actin ATP Hydrolysis Studied by QM/MM Calculations

Efficient Hydrogen Generation from Ammonia Borane Hydrolysis on a Tandem Ruthenium–Platinum–Titanium Catalyst

Hydrolysis of ammonia borane (NH3BH3, AB) involves multiple undefined steps and complex adsorption and activation, so single or dual sites are not enough for the rapidity of the multiple processes. Designing multi‐site catalysts is necessary to enhance the catalytic performance of AB hydrolysis reactions but revealing the matching reaction mechanisms of AB hydrolysis is a great challenge. In this work, we propose to construct RuPt‐Ti multi‐site catalysts with the metal‐support synergy effect to clarify the multi‐site tandem activation mechanism of AB hydrolysis. Experimental and theoretical studies reveal that the multi‐site tandem mode can respectively promote the activation of NH3BH3 and H2O molecules on the Ru and Pt sites as well as facilitate the fast transfer of *H and the desorption of H2 on Ti sites at the same time. RuPt‐Ti multi‐site catalysts exhibit the highest turnover frequency (TOF) of 1293 min‐1 for AB hydrolysis reaction, outperforming the single‐site Ru, dual‐site RuPt and Ru‐Ti catalysts. This study proposes a multi‐site tandem concept for accelerating the dehydrogenation of hydrogen storage material, aiming to contribute to the development of cleaner, low‐carbon, and high‐performance hydrogen production systems.

Efficient Hydrogen Generation from Ammonia Borane Hydrolysis on a Tandem Ruthenium-Platinum-Titanium Catalyst.

Hydrolysis of ammonia borane (NH3BH3, AB) involves multiple undefined steps and complex adsorption and activation, so single or dual sites are not enough for the rapidity of the multiple processes. Designing multi-site catalysts is necessary to enhance the catalytic performance of AB hydrolysis reactions but revealing the matching reaction mechanisms of AB hydrolysis is a great challenge. In this work, we propose to construct RuPt-Ti multi-site catalysts with the metal-support synergy effect to clarify the multi-site tandem activation mechanism of AB hydrolysis. Experimental and theoretical studies reveal that the multi-site tandem mode can respectively promote the activation of NH3BH3 and H2O molecules on the Ru and Pt sites as well as facilitate the fast transfer of *H and the desorption of H2 on Ti sites at the same time. RuPt-Ti multi-site catalysts exhibit the highest turnover frequency (TOF) of 1293 min-1 for AB hydrolysis reaction, outperforming the single-site Ru, dual-site RuPt and Ru-Ti catalysts. This study proposes a multi-site tandem concept for accelerating the dehydrogenation of hydrogen storage material, aiming to contribute to the development of cleaner, low-carbon, and high-performance hydrogen production systems.

Preparation and antibacterial properties of β-SiAlON/AlN composite ceramics

In this study, β-SiAlON/aluminum nitride (AlN) composite ceramics were synthesized using a wet-mixing method at 1500 °C under a N2 atmosphere. X-ray diffraction and scanning electron microscopy were used to characterize the ceramics before and after immersing them in water for 7 d. The change in pH and release of ammonia nitrogen were studied to investigate the reaction and antibacterial mechanisms of AlN hydrolysis. The effects of the AlN content on the phase composition, microstructure, chemical properties, and antibacterial efficacy of the composite ceramics were investigated. As the AlN content increased, the antibacterial efficiency gradually increased. The antibacterial efficiency of the composite ceramic with an AlN content of 60 wt% was 100%, indicating that an increase in pH and amount of ammonia nitrogen could synergistically enhance the antibacterial effect. However, in a lysogeny broth medium, the buffering effect of the culture medium and promotion of bacterial proliferation may reduce the antibacterial efficiency. Therefore, β-SiAlON/AlN composite ceramics show considerable potential for antibacterial applications.

QM/MM study of the catalytic reaction of aphid myrosinase

Brevicoryne brassicae, an aphid species, exclusively consumes plants from the Brassicaceae family and employs a sophisticated defense mechanism involving a myrosinase enzyme that breaks down glucosinolates obtained from its host plants. In this work, we employed combined quantum mechanical and molecular mechanical (QM/MM) calculations and molecular dynamics (MD) simulations to study the catalytic reaction of aphid myrosinase. A proper QM region to study the myrosinase reaction should contain the whole substrate, models of Gln-19, His-122, Asp-124, Asn-166, Glu-167, Lys-173, Tyr-180, Val-228, Tyr-309, Tyr-346, Ile-347, Glu-374, Glu-423, Trp-424, and a water molecule. The calculations show that Asp-124 and Glu-423 must be charged, His-122 must be protonated on NE2, and Glu-167 must be protonated on OE2. Our model reproduces the anomeric retaining characteristic of myrosinase and indicates that the deglycosylation reaction is the rate-determining step of the reaction. Based on the calculations, we propose a reaction mechanism for aphid myrosinase-mediated hydrolysis of glucosinolates with an overall barrier of 15.2 kcal/mol. According to the results, removing a proton from Arg-312 or altering it to valine or methionine increases glycosylation barriers but decreases the deglycosylation barrier.

Understanding the hydrolysis mechanism of cyanogen chloride on copper and chromium surfaces

AbstractCyanogen chloride (CNCl) is a highly toxic agent, but there is currently a lack of research on the catalytic hydrolysis reaction of CNCl on metal surfaces. The low efficiency and unclear mechanism of CNCl hydrolysis reaction have hampered the development and enhancement of protective equipment. In this work, we focused on investigating the adsorption behavior and hydrolysis mechanism of CNCl on copper and chromium surfaces through first‐principle methods. Our findings revealed the most stable adsorption configuration of CNCl on metal surfaces and its terminal flipping behavior during the hydrolysis process. Subsequently, we designed and studied a series of CNCl hydrolysis reaction pathways, primarily involving C‐terminal intermediates. Notably, the adsorption energy of CN* displayed strong linear scaling relationships with that of other key reaction intermediates, directly influencing the activity and selectivity of CNCl hydrolysis. By employing the adsorption energy expression based on the intrinsic properties of substrates and adsorbates, we extended them to identify the adsorption energies of various complex reaction intermediates involved in CNCl hydrolysis. This comprehensive understanding of the reaction mechanism on metal surfaces provides a theoretical foundation and innovative perspective for the further exploration of CNCl hydrolysis catalysts.

EFFECTIVE POLYMER DECORATION ON NICKEL-IMINE COMPLEX TO ENHANCE CATALYTIC HYDROGEN EVOLUTION

Since fossil fuels are rapidly depleting, finding alternative energy sources is becoming increasingly important. Among these alternatives, hydrogen (H2) is the most viable option. In hydrogen evolution systems, supported metal catalysts enhance the catalytic activity in the hydrolysis reaction by increasing the surface area. Therefore, this research focuses on preparing three different polymer-decorated Nickel-Imine complex catalysts (Ni@EC, Ni@EC-250, Ni@ECM) to improve their efficiency. To achieve the catalysts, a Nickel-Imine complex [1] was supported on three different polymers (EC, EC-250, and ECM). The catalysts (Ni@EC, Ni@EC-250, Ni@ECM) were then utilized to generate hydrogen from NaBH4 hydrolysis. The hydrogen evolution rates for Ni@EC, Ni@EC-250, and Ni@ECM catalysts were found as 6879; 15576; 8830 and 15459; 28689; 23417 mL H2 gcat-1.min-1, respectively at 30 oC and 50 oC. Results indicate that the Ni@EC-250 catalyst exhibited the best activity. Consequently, the subsequent steps of the catalytic hydrolysis reaction were studied using Ni@EC-250. The activation energy of the Ni@EC-250 catalyst was estimated at 39.255 kJ.mol-1. The reusability tests demonstrate that Ni@EC-250 remains active in sodium borohydride hydrolysis even after five runs. Technical abbreviations are defined upon first use. This study elucidates the reaction mechanism and kinetic data of catalytic sodium borohydride hydrolysis at various temperatures.

Kinetics and Reaction Mechanism of Acid-Catalyzed Hydrolysis of Propyl Methanoate in Aqueous Solvent of Propanol-2 and its effect on Activation Parameters

The rate of acid catalyzed hydrolysis of propyle methanoate has been studied in the presence of 0.1N-HCI in water-propanol mixture containing up to 30-70% (v/v) has been studied over the temperature ranging from 20-400C. The specific rate constant values followed first order kinetics and decreases with increasing proportion of organic solvent. Number of water molecules associated with activated complex has also been calculated at different temperature with the help of slopes of logk against different mole % of waters. Iso-kinetic temperature was calculated and its numerical values are found to be greater than 300, is an indication of great solvent-solute interaction during the hydrolysis of ester.

Kinetic models for water sorption and a hydrolysis reaction with poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBH)

Biodegradable polymers, including polyhydroxyalkanoate (PHA), have attracted attention because plastic waste is entering the ocean and causing problems. Controlling the rate of PHA degradation is essential for expanding its application, and fundamental studies on the reaction mechanisms are needed. The purpose of this study is to experimentally verify the mechanisms of water sorption and hydrolysis reactions involving poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBH), a type of PHA, and construct a model. In this study, the water sorption process was measured by near-infrared (NIR) spectroscopy and Fourier transform infrared spectroscopic (FTIR) imaging. From the results, we found that water sorption on PHBH proceeds by non-Fickian diffusion, two kinetic processes involving adsorption and diffusion. The reaction rate of PHBH hydrolysis was determined by gel permeation chromatography (GPC) analysis, and a model was developed to predict PHBH degradation during hydrolysis from the experimental results. Furthermore, we proposed a reaction-diffusion model that combines water sorption and hydrolysis reactions. As a result, the degradation of PHBH plates with different thicknesses can be predicted for this first time.

Human 2'-Deoxynucleoside 5'-Phosphate N-Hydrolase 1: Mechanism of 2'-Deoxyuridine 5'-Monophosphate Hydrolysis.

The enzyme 2'-deoxynucleoside 5'-phosphate N-hydrolase 1 (DNPH1) catalyzes the N-ribosidic bond cleavage of 5-hydroxymethyl-2'-deoxyuridine 5'-monophosphate to generate 2-deoxyribose 5-phosphate and 5-hydroxymethyluracil. DNPH1 accepts other 2'-deoxynucleoside 5'-monophosphates as slow-reacting substrates. DNPH1 inhibition is a promising strategy to overcome resistance to and potentiate anticancer poly(ADP-ribose) polymerase inhibitors. We solved the crystal structure of unliganded human DNPH1 and took advantage of the slow reactivity of 2'-deoxyuridine 5'-monophosphate (dUMP) as a substrate to obtain a crystal structure of the DNPH1:dUMP Michaelis complex. In both structures, the carboxylate group of the catalytic Glu residue, proposed to act as a nucleophile in covalent catalysis, forms an apparent low-barrier hydrogen bond with the hydroxyl group of a conserved Tyr residue. The crystal structures are supported by functional data, with liquid chromatography-mass spectrometry analysis showing that DNPH1 incubation with dUMP leads to slow yet complete hydrolysis of the substrate. A direct UV-vis absorbance-based assay allowed characterization of DNPH1 kinetics at low dUMP concentrations. A bell-shaped pH-rate profile indicated that acid-base catalysis is operational and that for maximum kcat/KM, two groups with an average pKa of 6.4 must be deprotonated, while two groups with an average pKa of 8.2 must be protonated. A modestly inverse solvent viscosity effect rules out diffusional processes involved in dUMP binding to and possibly uracil release from the enzyme as rate limiting to kcat/KM. Solvent deuterium isotope effects on kcat/KM and kcat were inverse and unity, respectively. A reaction mechanism for dUMP hydrolysis is proposed.

Advances in Metal-Organic Frameworks for the Removal of Chemical Warfare Agents: Insights into Hydrolysis and Oxidation Reaction Mechanisms.

The destruction of chemical warfare agents (CWAs) is a crucial area of research due to the ongoing evolution of toxic chemicals. Metal-organic frameworks (MOFs), a class of porous crystalline solids, have emerged as promising materials for this purpose. Their remarkable porosity and large surface areas enable superior adsorption, reactivity, and catalytic abilities, making them ideal for capturing and decomposing target species. Moreover, the tunable networks of MOFs allow customization of their chemical functionalities, making them practicable in personal protective equipment and adjustable to dynamic environments. This review paper focuses on experimental and computational studies investigating the removal of CWAs by MOFs, specifically emphasizing the removal of nerve agents (GB, GD, and VX) via hydrolysis and sulfur mustard (HD) via selective photooxidation. Among the different MOFs, zirconium-based MOFs exhibit extraordinary structural stability and reusability, rendering them the most promising materials for the hydrolytic and photooxidative degradation of CWAs. Accordingly, this work primarily concentrates on exploring the intrinsic catalytic reaction mechanisms in Zr-MOFs through first-principles approximations, as well as the design of efficient degradation strategies in the aqueous and solid phases through the establishment of Zr-MOF structure-property relationships. Recent progress in the tuning and functionalization of MOFs is also examined, aiming to enhance practical CWA removal under realistic battlefield conditions. By providing a comprehensive overview of experimental findings and computational insights, this review paper contributes to the advancement of MOF-based strategies for the destruction of CWAs and highlights the potential of these materials to address the challenges associated with chemical warfare.

Rattle-structured CuO/Co3O4@C microspheres, a potent bifunctional catalyst for hydrogen production from ammonia borane hydrolysis and methanolysis

Engineering and fabricating cost-effective and high-performing bifunctional catalysts for ammonia borane (AB) hydrolysis and methanolysis is paramount for their commercial availability. A series of rattle-structured CuO/Co3O4@C microsphere bifunctional catalysts for AB hydrolysis and methanolysis were produced using a simple hard template etching approach. The CuO/Co3O4@C-4 (4 refers to designed the mole ratio of Cu/Co) exhibits the best activity with TOF of 18.8 and 26.8 molH2·molcat-1·min−1 for AB hydrolysis and methanolysis, respectively. It is discovered that the excellent performance is mainly attributed to its unique rattle structure and the synergetic effect between Co3O4 and CuO. Kinetic isotope effect (KIE) experiments and infrared spectroscopy were applied to investigate AB hydrolysis and methanolysis reaction mechanisms. A suggested mechanism for AB methanolysis on rattle-structured CuO/Co3O4@C-4 is proposed based on the experiment results. This work could provide useful guidance for the construction of high-performance bifunctional catalysts for AB hydrolysis and methanolysis for hydrogen production.

Mechanism of dissolution reactivity and reactions of various calcium borate glasses and glass-ceramics

This study investigated the effect of calcium addition on boron coordination and ion release in deionized water (DIW) of five melt-quench-derived compositions: xCaO-(100-x)B2O3 (x=25, 27, 33, 38 and 48 mol%) and one sol-gel-derived 48CaO-52B2O3 glass. The mechanism of hydration and hydrolysis reactions was elaborated based on ionic release and structural change pre- and post- ageing in DIW. For melt-quench-derived glasses, within 8 h ageing, the hydration reactions were more rapid than the hydrolysis reactions, resulting in solution pH increase, where ionic release was more dependent on composition than boron coordination. At longer ageing times, hydration and hydrolysis reactions occurred simultaneously, leading to solution pH stabilization, and calcium and boron release decreased with an increase in the boron tetrahedral fraction (N4) in glasses. Non-bridging-oxygens in the melt-quench-derived 48CaO-52B2O3 glass-ceramic and hydroxyl groups in the equivalent sol-gel-derived glass fostered calcium and boron release. All glass formulations demonstrated higher N4 post DIW exposure.

Kinetics of Egg-Yolk Protein Hydrolysis and Properties of Hydrolysates.

Lecithin-free egg yolk (LFEY) is a byproduct of the extraction of egg-yolk phospholipids, which contain approximately 46% egg yolk proteins (EYPs) and 48% lipids. The enzymatic proteolysis is the alternative to increase the commercial value of LFEY. The kinetics of proteolysis in full-fat and defatted LFEY with Alcalase 2.4 L was analyzed in terms of the Weibull and Michaelis-Menten models. A product inhibition effect was also studied in the full-fat and defatted substrate hydrolysis. The molecular weight profile of hydrolysates was analyzed by gel filtration chromatography. Results pointed out that the defatting process did not importantly affect the maximum degree of hydrolysis (DHmax) in the reaction but rather the time at which DHmax is attained. The maximum rate of hydrolysis (Vmax) and the Michaelis-Menten constant KM were higher in the hydrolysis of the defatted LFEY. The defatting process might have induced conformational changes in the EYP molecules, and this affected their interaction with the enzyme. Consequently, the enzymatic reaction mechanism of hydrolysis and the molecular weight profile of peptides were influenced by defatting. A product inhibition effect was observed when adding 1% hydrolysates containing peptides lower than 3 kDa at the beginning of the reaction with both substrates.

Synthesis of Acrylate Dual-Tone Resists and the Effect of Their Molecular Weight on Lithography Performance and Mechanism: An Investigation.

Acrylate photoresists have gained considerable attention in recent years owing to their high resolution, high sensitivity, and versality. In this work, a series of thermally stable copolymers are synthesized by introducing an isobornyl group, and well characterized using Fourier transform infrared spectroscopy (FT-IR) and nuclear magnetic resonance spectra (1H-NMR). The effects of polymerization conditions on the molecular weight and their further influence on lithography are explored. By analyzing the thermal properties, film-forming capabilities, and the patterning behavior of these copolymers, a direct correlation between lithography performance and polymerization conditions is established via the molecular weight. In addition, the baking temperature of lithography is also optimized by atomic force microscopy (AFM), after which a line resolution of 0.1 μm is observed under the exposure of a 248 nm UV light and electron beam. Notably, our synthesized photoresist displays dual-tone resist characteristics when different developers are applied, and the reaction mechanism of acid-catalyzed hydrolysis is finally proposed by comparing the structural changes before and after exposure.

®Optimization of the Hydrolysis Reaction Process in the Synthesis of 4‐Aminoantipyrine by Response Surface Methodology and its Kinetics

AbstractIn this paper, a unique hydrolysis reaction process for the production of 4‐Aminoantipyrine (AA) is investigated. A liquid‐phase analytical method for AA is established, and the amount of sulfuric acid, reaction temperature, reaction time are studied. On the basis of single factor experiments, the response surface method (RSM) is used to systematically optimize the conditions of the hydrolysis reaction. The optimum conditions are n(AT‐SO4): n(H2SO4)=0.73, the reaction temperature is 98 °C, the reaction time is 91 min, and the AA yield reaches 90.80 %. Compared with the previous process, the yield of AA is improved and colloids are significantly reduced. Under optimum process conditions, a kinetic model is constructed in the range of 358 K–373 K, which activation energy, Ea=33.21 kJ/mol, and the pre‐exponential factor, A=1586.84. In addition, the product AA is characterized by IR analysis, LC‐MS analysis, GC‐MS analysis and hydrolysis reaction mechanism are investigated.

Understanding the mechanism of the sulfur mustard hydrolysis reaction on the atomistic level from experiment and first-principles simulations

After World War II, the Baltic Sea was contaminated by dumping unused sulfur mustard (SM) and other chemical warfare agents (CWAs), which now constitutes a huge environmental hazard. We use both experimental and theoretical methods to understand the reactivity of SM in water, in particular the hydrolysis, which is one of the chemical reactions leading to the neutralization of SM. Real conditions present in the Baltic Sea are represented by performing Car-Parrinello molecular dynamics simulations for sulfur mustard in explicit water solution at finite temperature. We study the relative occurrence and stability of various SM conformers in water and analyze the solute–solvent interactions, with special focus on the formation of intra- and intermolecular hydrogen bonds and their lifetime. A missing piece toward the understanding of the sulfonium cation formation and SM hydrolysis reaction is provided by obtaining the activation energy for SM decomposition in water solution from gas chromatography–mass spectrometry (GC-MS) experiments. The complex mechanism of SM hydrolysis is also studied by umbrella sampling simulations to obtain the free energy barrier for the sulfonium cation formation and to provide an atomistic view of the reaction process.

Road-blocker HSP disease mutation disrupts pre-organization for ATP hydrolysis in kinesin through a second sphere control

Kinesin motor proteins perform several essential cellular functions powered by the adenosine triphosphate (ATP) hydrolysis reaction. Several single-point mutations in the kinesin motor protein KIF5A have been implicated to hereditary spastic paraplegia disease (HSP), a lethal neurodegenerative disease in humans. In earlier studies, we have shown that a series of HSP-related mutations can impair the kinesin's long-distance displacement or processivity by modulating the order-disorder transition of the linker connecting the heads to the coiled coil. On the other hand, the reduction of kinesin's ATP hydrolysis reaction rate by a distal asparagine-to-serine mutation is also known to cause HSP disease. However, the molecular mechanism of the ATP hydrolysis reaction in kinesin by this distal mutation is still not fully understood. Using classical molecular dynamics simulations combined with quantum mechanics/molecular mechanics calculations, the pre-organization geometry required for optimal hydrolysis in kinesin motor bound to α/β-tubulin is determined. This optimal geometry has only a single salt-bridge (of the possible two) between Arg203-Glu236, putting a reactive water molecule at a perfect position for hydrolysis. Such geometry is also needed to create the appropriate configuration for proton translocation during ATP hydrolysis. The distal asparagine-to-serine mutation is found to disrupt this optimal geometry. Therefore, the current study along with our previous one demonstrates how two different effects on kinesin dynamics (processivity and ATP hydrolysis), caused by a different set of genotypes, can give rise to the same phenotype leading to HSP disease.

QM/MM Simulations for the Broken-Symmetry Catalytic Reaction Mechanism of Human Arginase I.

Human arginase I (HARGI) is a metalloprotein highly expressed in the liver cytosol and catalyzes the hydrolysis of l-arginine to form l-ornithine and urea. Understanding the reaction mechanism would be highly helpful to design new inhibitor molecules for HARGI as it is a target for heart- and blood-related diseases. In this study, we explored the hydrolysis reaction mechanism of HARGI with antiferromagnetic and ferromagnetic coupling between two Mn(II) ions at the catalytic site by employing molecular dynamics simulations coupled with quantum mechanics and molecular mechanics (QM/MM). The spin states, high-spin ferromagnetic couple (SMn1 = 5/2, SMn2 = 5/2), low-spin ferromagnetic couple (SMn1 = 1/2, SMn2 = 1/2), high-spin antiferromagnetic couple (SMn1 = 5/2, SMn2 = −5/2), and low-spin antiferromagnetic couple (SMn1 = 1/2, SMn2 = −1/2) are considered, and the calculated energetics for the complex of the substrate and HARGI are compared. The results show that the high-spin antiferromagnetic couple (SMn1 = 5/2, SMn2 = −5/2) is more stable than other spin states. The low-spin ferromagnetic and antiferromagnetic coupled states are highly unstable compared with the corresponding high-spin states. The high-spin antiferromagnetic couple (SMn1 = 5/2, SMn2 = −5/2) is stabilized by 0.39 kcal/mol compared with the ferromagnetic couple (SMn1 = 5/2, SMn2 = 5/2). The reaction mechanism is independent of spin states; however, the energetics of transition states and intermediates are more stable in the case of the high-spin antiferromagnetic couple (SMn1 = 5/2, SMn2 = −5/2) than the corresponding ferromagnetic state. It is evident that the calculated coupling constants are higher for antiferromagnetic states and, interestingly, superexchange coupling is found to occur between Mn(II) ions via hydroxide ions in a reactant. The hydroxide ion enhances the coupling interaction and initiates the catalytic reaction. It is also noted that the first intermediate structure where there is no superexchange coupling is similar to the known inhibitor 2(S)-amino-6-boronohexanoic acid.

Interfacial Adhesion in Silica-Silane Filled NR Composites: A Short Review.

We reviewed the accelerators, the hydrolysis and condensation reaction mechanism of bifunctional alkoxy silane, and the mechanism of zinc ion in natural rubber (NR) composites. NR composites transform into thermoset composites after vulcanization reaction with help of sulfur and accelerators. Bifunctional alkoxy silanes chemically bond between NR and inorganic silica. For alkoxy silane coupling with silica surface, hydrolysis reaction takes first and then condensation reaction with hydroxyl group in silica takes place. With help of zinc ion the reaction efficiency increases significantly. Zinc ion, a smart material that increases accelerator synergy, mechanism for improvements of interfacial adhesion between NR and silica was revisited.