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Substrate specificity in non-aqueous esterification catalyzed by commercial lipases activated by hydration-aggregation pretreatment was investigated. Four microbial lipases from Rhizopus japonicus, Burkholderia cepacia, Rhizomucor miehei, and Candida antarctica (fraction B) were used to study the effect of the carbon chain length of saturated fatty acid substrates on the esterification activity with methanol in n-hexane. Hydration-aggregation pretreatment had an activation effect on all lipases used, and different chain length dependencies of esterification activity for lipases from different origins were demonstrated. The effects of various acidic substrates with different degrees of unsaturation, aromatic rings, and alcohol substrates with different carbon chain lengths on esterification activity were examined using R. japonicus lipase, which demonstrated the most remarkable activity enhancement after hydration-aggregation pretreatment. Furthermore, in the esterification of myristic acid with methanol catalyzed by the hydrated-aggregated R. japonicus lipase, maximum reaction rate (5.43 × 10-5 mmol/(mg-biocat min)) and Michaelis constants for each substrate (48.5â¯mM for myristic acid, 24.7â¯mM for methanol) were determined by kinetic analysis based on the two-substrate Michaelis-Menten model.
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Exploring novel molecular photoswitches plays a crucial role in the field of photo-functional materials chemistry. In this study, we synthesized aza-diarylethenes with benzothiophene-S,S-dioxide as a part of hexatriene structure and investigated their photochromic properties. Unlike previously reported aza-diarylethenes, which exhibit fast thermally reversible photochromism, the compounds synthesized here exhibited pseudo-photochemically reversible photochromism. Due to their thermal stability, we successfully isolated the colored isomer. X-ray crystallographic analysis revealed for the first time that the colored isomer adopts a closed-ring structure with a bond between carbon and nitrogen atoms. Remarkably, these aza-diarylethenes exhibited not only photochemical ring-closing and ring-opening reactions but also thermal ring-closing and ring-opening reactions, driven by a thermal equilibrium between the open- and closed-ring isomers. This behavior, unprecedented for common diarylethenes, was elucidated through kinetic analysis, revealing an energy-level diagram for the thermal equilibrium between these isomers. Furthermore, 1H NMR spectroscopy revealed that both photochemically and thermally generated closed-ring isomers adopt the same structure, which was well explained based on the reaction mechanism of photochemical and thermal ring-closing reactions. These findings not only advance the field of aza-diarylethenes but also inspire future research in the development of new photoswitches.
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Iron insertion into porphyrins is an essential step in heme biosynthesis. In the coproporphyrin-dependent pathway, specific to monoderm bacteria, this reaction is catalyzed by the monomeric enzyme coproporphyrin ferrochelatase. In addition to the mechanistic details of the metalation of the porphyrin, the identification of the substrate access channel for ferrous iron to the active site is important to fully understand this enzymatic system. In fact, whether the iron reaches the active site from the distal or the proximal porphyrin side is still under debate. In this study we have thoroughly addressed this question in Listeria monocytogenes coproporphyrin ferrochelatase by X-ray crystallography, steady-state and pre-steady-state imidazole ligand binding studies, together with a detailed spectroscopic characterization using resonance Raman and UV-vis absorption spectroscopies in solution. Analysis of the X-ray structures of coproporphyrin ferrochelatase-coproporphyrin III crystals soaked with ferrous iron shows that iron is present on both sides of the porphyrin. The kinetic and spectroscopic study of imidazole binding to coproporphyrin ferrochelataseiron coproporphyrin III clearly indicates the presence of two possible binding sites in this monomeric enzyme that influence each other, which is confirmed by the observed cooperativity at steady-state and a biphasic behavior in the pre-steady-state experiments. The current results are discussed in the context of the entire heme biosynthetic pathway and pave the way for future studies focusing on protein-protein interactions.
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Coproporfirinas , Ferroquelatase , Imidazóis , Ferroquelatase/metabolismo , Ferroquelatase/química , Imidazóis/química , Imidazóis/metabolismo , Cristalografia por Raios X , Coproporfirinas/metabolismo , Coproporfirinas/química , Listeria monocytogenes/enzimologia , Heme/metabolismo , Heme/química , Proteínas de Bactérias/metabolismo , Proteínas de Bactérias/química , Domínio Catalítico , Ferro/química , Ferro/metabolismo , Ligação ProteicaRESUMO
Landfilled metallurgical residues are valuable raw materials for the recovery of strategic vanadium resources. However, efficient separation of vanadium from these residues is challenging due to its strong oxidation resistance and coating within silicate inclusions. To address this issue, this study proposes an enhanced leaching process utilizing the synergistic effect of O3-catalyzed ultrasonic field in a low concentration sulfuric acid system. Results show that following a 10-minute O3 and ultrasonic treatment, the direct leaching rate of vanadium experienced a remarkable 46.7 % increase. Quenching experiments revealed a hierarchical order of active species within the reaction process:â OH >â O2-> H+, withâ OH oxidation exhibiting the most pronounced capacity for disrupting the inclusion structure. Electron Paramagnetic Resonance analysis indicated that the highestâ OH yield arose from the combined application of ultrasound and ozone. Kinetic investigations demonstrated that the vanadium leaching process is governed by interfacial chemical reactions. The activation energy of vanadium oxidation leaching under ultrasonic-O3 conditions was determined to be 40.41 kJ/mol, representing a 20.19 % reduction compared to ultrasonic conditions alone. Through the integration of analysis, characterization, and comparative evaluations, it was discerned that the synergistic impact of ultrasonic and ozone treatments significantly enhances the breakdown of silicate inclusions by low-concentration HF, particularly in the conversion of SiOSi bonds into SiOH bonds and SiF bonds. In summary, the refined leaching methodology incorporating ozone catalysis in conjunction with ultrasonic treatment provides a new idea for the separation and extraction of refractory residual vanadium.
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PURPOSE: Fed-batch cultures have rarely been used in single cell protein (SCP) research. This work evaluated multiple yeast species for suitability as SCP cultivated using glucose- and sucrose-based substrate and performed in-depth studies of fed-batch SCP cultivation kinetics for selected yeasts, including determination of specific crude nitrogen-to-protein conversion factors. METHODS: SCP was cultivated using fully synthetic media in flask batch or bioreactor fed-batch cultures. Crude nitrogen and nucleic acid content were determined using the Dumas method and fluorescence assay kits, respectively. RESULTS: C. utilis compared favorably to other yeasts in flask batch cultures in terms of process yield (0.52 ± 0.01 gx gs-1) and crude nitrogen content (10.0 ± 0.5 and 9.9 ± 0.5%CDW for glucose and sucrose, respectively). This is the first time biomass composition data was reported for SCP cultivated in fed-batch mode. C. utilis crude nitrogen content was consistent across the tested conditions (protein content stabilized around 50%CDW in fed-batch), while that of the benchmark yeast S. cerevisiae was higher in batch cultures and at the beginning of fed-batch relative to the end (protein content decreased over time and stabilized around 43%CDW). Total nucleic acid content of the yeasts was similar (6.8%CDW and 6.3%CDW, for C. utilis and S. cerevisiae, respectively), with crude nitrogen-to-protein conversion factors of 4.97 and 5.80. CONCLUSION: This study demonstrated the suitability of C. utilis as SCP, notably the robustness of its crude nitrogen content (as an indicator of protein content) across batch and fed-batch conditions, compared to that of the benchmark yeast S. cerevisiae.
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Washing aggregate sludge (WAS), a waste collected from aggregate quarries, is examined for its application as a partial substitute of ordinary portland cement (OPC). The raw WAS initially dried, ground, and then subjected to 700 °C and 900 °C. In this study, various paste and mortar mixtures were produced to investigate the pozzolanic property and environmental impacts of raw WAS and treated WAS at a selected temperature of 700 °C. The pozzolanic activity of both raw and treated WAS at 700 °C was verified using several tests, including X-ray diffraction (XRD), Frattini test, strength-based evaluation, and thermal analysis. The calcium-silicate-hydrate (C-S-H), portlandite (Ca(OH)2), calcium silicates (C2S and C3S), and calcite (CaCO3) were identified as major reaction products indicating the participation of raw or treated WAS. While the reduced [CaO] concentration and location below the solubility curve confirmed the pozzolanic activity of both powders, the compressive strengths of blended mortars were also found greater than 75% compared to the reference mortar at all testing ages. Treated WAS demonstrated higher pozzolanic activity than raw WAS due to the reduced formation of Ca(OH)2 revealed by thermal and kinetic analysis at different time periods. Life cycle assessment resulted in the reduced CO2 emissions by the blended mortars containing either raw or treated WAS, which suggest their promising mechanical and environmental benefits.
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Materiais de Construção , Esgotos , Esgotos/química , Difração de Raios X , Compostos de Cálcio/químicaRESUMO
The RNA-induced silencing complex (RISC), which powers RNA interference (RNAi), consists of a guide RNA and an Argonaute protein that slices target RNAs complementary to the guide. We find that, for different guide-RNA sequences, slicing rates of perfectly complementary bound targets can be surprisingly different (>250-fold range), and that faster slicing confers better knockdown in cells. Nucleotide sequence identities at guide-RNA positions 7, 10, and 17 underlie much of this variation in slicing rates. Analysis of one of these determinants implicates a structural distortion at guide nucleotides 6-7 in promoting slicing. Moreover, slicing directed by different guide sequences has an unanticipated, 600-fold range in 3'-mismatch tolerance, attributable to guides with weak (AU-rich) central pairing requiring extensive 3' complementarity (pairing beyond position 16) to more fully populate the slicing-competent conformation. Together, our analyses identify sequence determinants of RISC activity and provide biochemical and conformational rationale for their action.
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Proteínas Argonautas , Conformação de Ácido Nucleico , RNA Guia de Sistemas CRISPR-Cas , Complexo de Inativação Induzido por RNA , Proteínas Argonautas/metabolismo , Proteínas Argonautas/genética , Proteínas Argonautas/química , Humanos , Complexo de Inativação Induzido por RNA/metabolismo , Complexo de Inativação Induzido por RNA/genética , Complexo de Inativação Induzido por RNA/química , Cinética , RNA Guia de Sistemas CRISPR-Cas/genética , RNA Guia de Sistemas CRISPR-Cas/metabolismo , Interferência de RNA , Sequência de Bases , Células HEK293RESUMO
Members of the SLC25 mitochondrial carrier family link cytosolic and mitochondrial metabolism and support cellular maintenance and growth by transporting compounds across the mitochondrial inner membrane. Their monomeric or dimeric state and kinetic mechanism have been a matter of long-standing debate. It is believed by some that they exist as homodimers and transport substrates with a sequential kinetic mechanism, forming a ternary complex where both exchanged substrates are bound simultaneously. Some studies, in contrast, have provided evidence indicating that the mitochondrial ADP/ATP carrier (SLC25A4) functions as a monomer, has a single substrate binding site, and operates with a ping-pong kinetic mechanism, whereby ADP is imported before ATP is exported. Here we reanalyze the oligomeric state and kinetic properties of the human mitochondrial citrate carrier (SLC25A1), dicarboxylate carrier (SLC25A10), oxoglutarate carrier (SLC25A11), and aspartate/glutamate carrier (SLC25A13), all previously reported to be dimers with a sequential kinetic mechanism. We demonstrate that they are monomers, except for dimeric SLC25A13, and operate with a ping-pong kinetic mechanism in which the substrate import and export steps occur consecutively. These observations are consistent with a common transport mechanism, based on a functional monomer, in which a single central substrate-binding site is alternately accessible.
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Transportadores de Ácidos Dicarboxílicos , Humanos , Cinética , Transportadores de Ácidos Dicarboxílicos/metabolismo , Transportadores de Ácidos Dicarboxílicos/genética , Mitocôndrias/metabolismo , Mitocôndrias/genética , Proteínas de Transporte da Membrana Mitocondrial/metabolismo , Proteínas de Transporte da Membrana Mitocondrial/genética , Multimerização Proteica , Sistemas de Transporte de Aminoácidos Acídicos/metabolismo , Sistemas de Transporte de Aminoácidos Acídicos/genética , Proteínas de Transporte de Ânions/metabolismo , Proteínas de Transporte de Ânions/genética , Proteínas de Transporte de Ânions/química , Proteínas Mitocondriais/metabolismo , Proteínas Mitocondriais/genética , Antiporters/metabolismo , Antiporters/genética , Antiporters/química , Translocases Mitocondriais de ADP e ATP/metabolismo , Translocases Mitocondriais de ADP e ATP/genética , Transporte Biológico , Transportadores de Ânions Orgânicos/metabolismo , Transportadores de Ânions Orgânicos/genética , Transportadores de Ânions Orgânicos/química , Trifosfato de Adenosina/metabolismo , Proteínas de Transporte , Proteínas de Membrana TransportadorasRESUMO
This paper investigates the combustion characteristics and pollutant emission patterns of the mixed combustion of lignite (L) and torrefied pine wood (TPW) under different blending ratios. Isothermal combustion experiments were conducted in a fixed bed reaction system at 800 °C, and pollutant emission concentrations were measured using a flue gas analyzer. Using scanning electron microscopy (SEM) and BET (nitrogen adsorption) experiments, it was found that torrefied pine wood (TPW) has a larger specific surface area and a more developed pore structure, which can facilitate more complete combustion of the sample. The results of the non-isothermal thermogravimetric analysis show that with the TPW blending ratio increase, the entire combustion process advances, and the ignition temperature, maximum peak temperature, and burnout temperature all show a decreasing trend. The kinetic equations of the combustion reaction process of mixed gas were calculated by Flynn-Wall-Ozawa (FWO) and Kissinger-Akahira-Sunose (KAS) kinetic equations. The results show that the blending of TPW reduces the activation energy of the combustion reaction of the mixed fuel. When the TPW blending ratio is 80%, the activation energy values of the mixed fuel are the lowest at 111.32 kJ/mol and 104.87 kJ/mol. The abundant alkali metal ions and porous structure in TPW reduce the conversion rates of N and S elements in the fuel to NO and SO2, thus reducing the pollutant emissions from the mixed fuel.
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In this study, we report the successful development of a novel high-sensitivity intensity-based Surface Plasmon Resonance imaging (SPRi) biosensor and its application for detecting molecular interactions. By optimizing the excitation wavelength and employing a wavelength division multiplexing (WDM) algorithm, the system can determine the optimal excitation wavelength based on the initial refractive index of the sample without adjusting the incidence angle. The experimental results demonstrate that the refractive index resolution of the system reaches 1.77×10-6 RIU. Moreover, it can obtain the optimal excitation wavelength for samples with an initial refractive index in the range of 1.333 to 1.370 RIU and accurately monitor variations within the range of 0.0037 RIU without adjusting the incidence angle. Additionally, our new SPRi technique realized real-time detection of high-throughput biomolecular binding processes, enabling analysis of kinetic parameters. This research is expected to advance the development of more accurate SPRi technologies for molecular interaction analysis.
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Técnicas Biossensoriais , Ressonância de Plasmônio de Superfície , Ressonância de Plasmônio de Superfície/métodos , Técnicas Biossensoriais/métodos , Algoritmos , Refratometria , Ensaios de Triagem em Larga Escala/métodos , CinéticaRESUMO
Sigma-class glutathione transferase (GST) proteins with dual GST and prostaglandin synthase (PGS) activities play a crucial role in the establishment of Clonorchis sinensis infection. Herein, we analyzed the structural and enzymatic properties of sigma-class GST (CsGST-σ) proteins to obtain insight into their antioxidant and immunomodulatory functions in comparison with mu-class GST (CsGST-µ) proteins. CsGST-σ proteins conserved characteristic structures, which had been described in mammalian hematopoietic prostaglandin D2 synthases. Recombinant forms of these CsGST-σ and CsGST-µ proteins expressed in Escherichia coli exhibited considerable degrees of GST and PGS activities with substantially different specific activities. All recombinant proteins displayed higher affinities toward prostaglandin H2 (PGS substrate; average Km of 30.7 and 3.0 µm for prostaglandin D2 [PGDS] and E2 synthase [PGES], respectively) than those toward CDNB (GST substrate; average Km of 1,205.1 µm). Furthermore, the catalytic efficiency (Kcat/Km) of the PGDS/PGES activity was higher than that of GST activity (average Kcat/Km of 3.1, 0.7, and 7.0×10-3 s-1µm-1 for PGDS, PGES, and GST, respectively). Our data strongly suggest that the C. sinensis sigma- and mu-class GST proteins are deeply involved in regulating host immune responses by generating PGD2 and PGE2 in addition to their roles in general detoxification.
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Clonorchis sinensis , Glutationa Transferase , Oxirredutases Intramoleculares , Glutationa Transferase/metabolismo , Glutationa Transferase/química , Glutationa Transferase/genética , Clonorchis sinensis/enzimologia , Clonorchis sinensis/genética , Animais , Oxirredutases Intramoleculares/metabolismo , Oxirredutases Intramoleculares/química , Oxirredutases Intramoleculares/genética , Proteínas Recombinantes/metabolismo , Proteínas Recombinantes/genética , Proteínas Recombinantes/química , Lipocalinas/metabolismo , Lipocalinas/genética , Lipocalinas/química , Lipocalinas/imunologia , Escherichia coli/genética , Prostaglandina H2/metabolismo , Prostaglandina H2/química , CinéticaRESUMO
CRISPR/Cas systems have been widely employed for nucleic acid biosensing and have been further advanced for mutation detection by virtue of the sequence specificity of crRNA. However, existing CRISPR-based genotyping methods are limited by the mismatch tolerance of Cas effectors, necessitating a comprehensive screening of crRNAs to effectively distinguish between wild-type and point-mutated sequences. To circumvent the limitation of conventional CRISPR-based genotyping, here, we introduce Single-Molecule kinetic Analysis via a Real-Time digital CRISPR/Cas12a-assisted assay (SMART-dCRISPR). SMART-dCRISPR leverages the differential kinetics of the signal increase in CRISPR/Cas systems, which is modulated by the complementarity between crRNA and the target sequence. It employs single-molecule digital measurements to discern mutations based on kinetic profiles that could otherwise be obscured by variations in the target concentrations. We applied SMART-dCRISPR to genotype notable mutations in SARS-CoV-2, point mutation (K417N) and deletion (69/70DEL), successfully distinguishing wild-type, Omicron BA.1, and Omicron BA.2 SARS-CoV-2 strains from clinical nasopharyngeal/nasal swab samples. Additionally, we introduced a portable digital real-time sensing device to streamline SMART-dCRISPR and enhance its practicality for point-of-care settings. The combination of a rapid and sensitive isothermal CRISPR-based assay with single-molecule kinetic analysis in a portable format significantly enhances the versatility of CRISPR-based nucleic acid biosensing and genotyping.
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Técnicas Biossensoriais , COVID-19 , Sistemas CRISPR-Cas , SARS-CoV-2 , Sistemas CRISPR-Cas/genética , SARS-CoV-2/genética , SARS-CoV-2/isolamento & purificação , Técnicas Biossensoriais/métodos , Cinética , Humanos , COVID-19/virologia , COVID-19/diagnóstico , Mutação , Técnicas de Genotipagem/métodos , GenótipoRESUMO
Ultrasonic technology has a significant degassing effect and can increase the efficiency of hydrogen production in the proton exchange membrane electrolysis of water. However, further research is needed to understand its influence mechanism on hydrogen bubbles. In this work, a kinetic analysis is performed to investigate the principle of hydrogen production and the kinetic behaviour of hydrogen bubble evolution by applying the ultrasonic amplification technique under static and flow dynamics in the proton exchange membrane electrolysis cell. The evolution of hydrogen bubbles in the static and in the flow dynamic of the aqueous electrolyte solution under ultrasound was characterised by imaging. The results show that the aqueous electrolyte solution in the flow state reduces the size of hydrogen bubbles and increases the detachment speed compared to the static state, which promotes the process of hydrogen bubble evolution, and that the thermal effect of ultrasound on the temperature of the aqueous electrolyte solution in the flow state is very small compared to the static state and can be ignored. Ultrasound has different effects on the different stages of hydrogen bubble evolution. In the nucleation stage, the ultrasonic cavitation effect increases the highly reactive radicals such as â¢OH, Hâ¢, etc., and the mechanical vibration effect of ultrasound increases the nucleation sites, which are denser and more evenly distributed. In the growth phase, the ultrasonic cavitation effect and the mechanical vibration effect promote the breaking of hydrogen bonds of water molecules and improve mass transport, which promotes the growth of hydrogen bubbles, and the fluctuating energy of positive and negative ultrasound promotes the growth of hydrogen bubbles with the vibration speed. In the detachment phase, the radius of the hydrogen bubbles is influenced by the ultrasound. The radius of the hydrogen bubbles changes with the positive and negative ultrasonic pressure, the radius of the hydrogen bubbles at negative ultrasonic pressure increases, the positive ultrasonic pressure decreases, the changing effect of the radius of the hydrogen bubbles favours the detachment of the hydrogen bubbles. In the polymerisation phase, the ultrasound leads to increased polymerisation of the fine bubble streams. Ultrasound contributes to the hydrogen production effect of proton exchange membrane water electrolysis in actual operation.
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We employ UV/Vis Diffuse Reflectance spectroscopy directly coupled with a packed bed flow reactor to extract quantitative kinetic information. We use as a show-case the CuII/CuI redox dynamics during the reduction half cycle of the NH3-Selective Catalytic Reduction (SCR) on Cu-CHA catalysts. Our measurements enable quantification of the fraction of oxidized Cu, reconstructed by Multivariate Curve Resolution (MCR) together with monitoring of the gas-phase evolution during the reaction. These data both on the dynamics of the gas-phase and of the active site oxidation state have been used to assess the reduction half cycle rate equation and estimate the rate constant. Our results in terms of reaction orders and kinetic constant are in line with previous findings in the literature. Overall, our results demonstrate that the combined analysis of the UV spectra and of the gas-phase dynamics provides converging and unparalleled kinetic insight: this approach effectively resolves ambiguities concerning RHC kinetics and mechanism. More in general, this work provides evidence that operando spectroscopy can be used to extract quantitative kinetic information on catalytic cycles.
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Upper crossed syndrome (UCS) characterizes a prevalent postural dysfunction involving dysfunctional tone in the musculature of the shoulder girdle and cervicothoracic region. The discordant balance among the sternocleidomastoid, pectoralis major, levator scapulae, and upper trapezius musculature potentially precipitated cervical discomfort, thereby hindering routine activities and fostering the progression of UCS. Clinical scales are routinely utilized to assess and monitor the progress of rehabilitation; nonetheless, they often present inherent limitations. In contrast, advancements in three-dimensional (3D) motion capture technology furnish detailed kinematic data, thereby augmenting the capacity to objectively quantify and elucidate movement deficits with heightened precision. This case highlights the critical significance of employing kinematic analysis with Xsens as an outcome measure to elucidate the intricacies of UCS, thereby offering invaluable insights for therapeutic interventions in similar clinical scenarios and providing objective insights into movement biomechanics, muscular function, and functional limitations. Leveraging this information, clinicians can skillfully tailor treatment modalities to address underlying musculoskeletal imbalances, ultimately optimizing patient outcomes. In this case study, we examine the kinematic analysis of a 48-year-old office worker experiencing persistent headaches, restricted range of motion, and neck and shoulder pain over a four-month period. Despite prior interventions, symptomatology deteriorated, prompting consultation with a neurophysiotherapist. The evaluation revealed localized pain in the right shoulder, upper back, and neck, characterized by gradual onset and dull ache, exacerbated by activity and alleviated by rest and medication, without diurnal fluctuations. Physical examination delineated UCS features. Following the implementation of a four-week physiotherapy rehabilitation protocol, initial assessments utilizing Xsens gait motion analysis were undertaken. Subsequent to the rehabilitation program, significant improvements were noted across various parameters. These encompassed augmented range of motion, heightened muscular strength, and enhanced flexibility. Additionally, discernible enhancements were observed in posture and gait, characterized by the restoration of normal cervical spine curvature and an expanded range of motion.
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Co-pyrolysis is a promising technology for industrial organic waste to utilize their unique resource and energy properties for efficient conversion into valuable products. This study was the first time to characterize the co-pyrolysis of waste textiles with Ca-rich industrial sludge and Fe-rich industrial sludge on a laboratory-scale fixed bed. The properties, mechanisms, gas, oil and carbon production were investigated as a function of temperature and mixing type. Co-pyrolysis increased the total weight loss from 50.05 % to 69.81 % for Ca-rich industrial sludge mixed with 50 % waste textiles and from 49.13 % to 70.01 % for Fe-rich industrial sludge mixed with 50 % waste textiles. The activation energy of co-pyrolysis was approximately 50 % lower compared to the pyrolysis of waste textiles alone. The optimal reaction model for the different reaction stages for all samples was three diffusion (D3). Co-pyrolysis resulted in lower CO and CO2 emission temperatures of about 25-110 °C and produced more short-chain organic compounds (C < 10). Co-pyrolysis produced more aldehydes and ketones organics. Moreover, co-pyrolysis char exhibited an elevated level of fatty alkyl side chains and bridge branching, as well as higher degrees of aromatization and stability. This study offers valuable insights into the potential application of pyrolysis for the management of Ca/Fe-rich industrial sludge and waste textiles, thereby serving as a basis for future utilization endeavors.
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Resíduos Industriais , Ferro , Esgotos , Têxteis , Esgotos/química , Cinética , Ferro/química , Pirólise , Cálcio/química , Gerenciamento de Resíduos/métodosRESUMO
This study is focused on the detailed examination of the combustion properties and kinetic analysis of a cellulose acetate fibrous bundle (CAFB), separated from used cigarette filters. It was shown that the faster rate of CAFB heating allows a large amount of heat to be supplied to a combustion system in the initial stages, where the increase in heating rate has a positive response to ignition behavior. The best combustion stability of CAFB is achieved at the lowest heating rate. Through the use of different kinetic methods, it was shown that combustion takes place through two series of consecutive reaction steps and one independent single-step reaction. By optimizing the kinetic parameters within the proposed reaction models, it was found that the steps related to the generation of levoglucosenone (LGO) (by catalytic dehydration of levoglucosan (LG)) and acrolein (by breakdown of glycerol during CAFB burning-which was carried out through glycerol adsorption on a TiO2 surface in a the developed dehydration mechanism) represent rate-controlling steps, which are strongly controlled by applied heating rate. Isothermal predictions have shown that CAFB manifests very good long-term stability at 60 °C (which corresponds to storage in a sea shipping container), while at 200 °C, it shows a sudden loss in thermal stability, which is related to the physical properties of the sample.
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CONTEXT: In cellular environments, the reduction of disulfide bonds is pivotal for protein folding and synthesis. However, the intricate enzymatic mechanisms governing this process remain poorly understood. This study addresses this gap by investigating a disulfide bridge reduction reaction, serving as a model for comprehending electron and proton transfer in biological systems. Six potential mechanisms for reducing the dimethyl disulfide (DMDS) bridge through electron and proton capture were explored. Thermodynamic and kinetic analyses elucidated the sequence of proton and electron addition. MD-PMM, a method that combines molecular dynamics simulations and quantum-chemical calculations, was employed to compute the redox potential of the mechanism. This research provides valuable insights into the mechanisms and redox potentials involved in disulfide bridge reduction within proteins, offering an understanding of phenomena that are challenging to explore experimentally. METHODS: All calculations used the Gaussian 09 software package at the MP2/6-311 + g(d,p) theory level. Visualization of the molecular orbitals and electron densities was conducted using Gaussview6. Molecular dynamics simulations were performed using GROMACS with the CHARMM36 force field. The PyMM program (Python Program for QM/MM Simulations Based on the Perturbed Matrix Method) is used to apply the Perturbed Matrix Method to MD simulations.
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Contaminations by pharmaceuticals, personal care products, and other emerging pollutants in water resources have become a seriously burgeoning issue of global concern in the first third of the twenty-first century. As societal reliance on pharmaceuticals continues to escalate, the inadvertent introduction of these substances into water reservoirs poses a consequential environmental threat. Therefore, the aim of this study was to investigate reductive degradation, particularly, catalytic hydrogenation regarding model pollutants such as diclofenac (DCF), ibuprofen (IBP), 17α-ethinylestradiol (EE2), or bisphenol-A (BPA), respectively, in aqueous solutions at lab scale. Iron bimetals (zero valent iron, ZVI, and copper, Cu, or nickel, Ni) as well as zero valent magnesium (Mg, ZVM) in combination with rhodium, Rh, or palladium, Pd, as hydrogenation catalysts (HK), were investigated. Studies were executed through various short-term batch experiments, with multiple sample collections, over a total range of 120 min. The results indicated that DCF was attenuated at over 90 % when exposed to Fe-Cu or a Fe-Ni bimetal (applied as a single model pollutant). However, when DCF was part of a mixture alongside with IBP, EE2, and BPA, the attenuation efficacy decreased to 79 % with Fe-Cu and 23 % with Fe-Ni. Conversely, both IBP and BPA exhibit notably low attenuation levels with both bimetals, less than 50 %, both deployed as single substances or in mixtures. No reaction (degradation) products could be identified employing LC-MS, but sometimes a release of the parent pollutant when applying an acetic acid buffer could be noted to a certain extent, suggesting adsorption processes on corrosion products such as iron hydroxide and/or oxides. Surprisingly, Mg in combination with Rh (Rh-HK) or Pd (Pd-HK) showed a significantly rapid decrease in the concentrations of DCF, EE2, and BPA, in part up to approximately 100 %, that is, within a few minutes only in part due to hydrogenation degradation reactions (related reaction products could actually be identified by LC-MS; adsorption processes were not observed here). Moreover, kinetic modeling of the DCF degradation with Mg-Rh-HK was conducted at different temperatures (15 °C, 20 °C, 25 °C, 35 °C) and varied initial concentrations (2.5 mg/L, 5.0 mg/L, 7.5 mg/L, 10.0 mg/L). The outcomes prove that the degradation of DCF at the Rh-HK's surface followed a modified first-order kinetics, most probably by catalytic hydrodehalogenation and subsequent hydrogenation of the aromatic moieties (molecular hydrogen was provided by the corrosion of Mg). From the determined reaction rate constants at four different temperatures, the activation energy was estimated to be 59.6 kJ/mol by means of the Arrhenius equation what is in good agreement with similar results reported in the literature. This coupled hydrodehalogenation and hydrogenation approach may be upscaled into a new promising technical process for comprehensively removing such pharmaceuticals and similar pollutants in sewage plants in a single step, furthermore, even in combination with adsorption by activated carbon and/or ozonation which have already been established at some sewage plants in Switzerland and Germany recently.
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Poluentes Químicos da Água , Poluentes Químicos da Água/química , Catálise , Preparações Farmacêuticas/química , Magnésio/química , Hidrogênio/química , Compostos Benzidrílicos/química , Metais/química , FenóisRESUMO
Spontaneous combustion of coal gangue (CG) hills has caused varieties of secondary disasters that seriously endanger the ecological environment of the world. The emission law of index gases and their oxidation kinetics during the secondary oxidation process of CG with different ranks of oxidation were studied by using the temperature programmed device and online mass spectrometer (MS). Fourier transform infrared spectroscopy (FTIR) was used to reveal the changes of the CG internal active functional groups. The results showed that the energy required for the combustion of CG with low rank of pre-oxidation was significantly lower than that of the raw sample. However, as the oxidation rank increased, due to amounts of volatile components were released in the process of oxidation reaction, the CG in the combustion process of the emission of index gases and its oxygen consumption rate gradually reduced; the rapid oxidation stage shifted to the direction of the high temperature. In this study, the risk of spontaneous combustion of CG after oxidation at 80 â under 3% oxygen concentration was the strongest. The results of this paper are of great guiding significance for exploring the spontaneous combustion characteristics of CG hills and their prevention by traditional covering method.