Hot air drying of lotus pollen at temperatures ranging from 40 to 70 °C was investigated experimentally. Results indicated that the whole drying process occurred in the falling rate period. Color ...analysis showed that lotus pollen suffered color deterioration. The antioxidant capacity decreased and the fat oxidation activity increased following drying. The carotenoid content exhibited significant loss when dried at 70 °C (p < .05). Zero-order, first-order, and fractional conversion models were employed to fit the experimental data for color profile, antioxidant capacity, and fat oxidation. The first-order fraction model can precisely describe the color change and the antioxidant capacity deterioration, while the kinetics of thiobarbituric acid reactive substances followed the linear model. There is a correlation between color, antioxidant activity, and fat oxidation.
The aim of this work was to clarify the dynamics behind the influence of ionic strength on the changes in drug release from large unilamellar vesicles (LUVs). For this purpose, we have investigated ...the transport of two different model drugs (caffeine and hydrocortisone) formulated into liposomes through different types of barriers with different retention properties (regenerated cellulose and the newly introduced biomimetic barrier, Permeapad®). Drug release from liposomes was studied utilizing the standard Franz diffusion cells. LUV dispersions were exposed to the isotonic, hypotonic and hypertonic environment (difference of 300 mOsm/kg between the initial LUVs and the environment) and experimental data treated with both linear and non-linear (Korsmeyer-Peppas) regression models. To alter the rigidity of the liposomal membranes, cholesterol was introduced in the liposomal barriers (up to 25% w/w). Korsmeyer-Peppas model was proven to be suited to analyse experimental data throughout the experimental time frame, providing important additive information in comparison to standard linear approximation. The obtained results are highly relevant as they improve the interpretation of drug release kinetics from LUVs under osmotic stress. Moreover, the findings can be utilized in the development of liposomal formulations intended for nose-to-brain targeted drug delivery.
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An iron‐incorporated α‐Ni(OH)2 nanosheet array catalyst characterized by hierarchical surface nanobelts and robust urea oxidation performance are reported. The unique single‐crystalline belt‐on‐sheet ...hierarchical nanostructure was identified and it endows more reactive edges for the Ni2+‐to‐Ni3+ pre‐oxidation process to boost the generation of active high‐valence species for the urea oxidation reaction (UOR). Benefitting from the optimal Fe concentration, the UOR activity was further optimized owing to the favorable reaction kinetics. With the synergistic benefits of the increased surface areas, improved charge transfer behavior, favorable reaction kinetics and excellent structural stability, the iron‐incorporated α‐Ni(OH)2 hierarchical nanosheet array catalyst displays significantly improved UOR performance with both high activity and outstanding operational stability. This work could guide the design of advanced UOR catalysts for wastewater treatment and clean energy production in the future.
An iron belt: A hierarchical belt‐on‐sheet iron‐incorporated α‐Ni(OH)2 nanosheet array catalyst was developed. This catalyst exhibits increased surface areas, improved charge‐transfer behavior, favorable reaction kinetics, and excellent structural stability for robust urea oxidation.
Understanding the drivers of aerobic methane (CH₄) oxidation (MOX) is paramount in assessing the current and potential future CH₄ emissions from freshwater aquatic systems. Regulation of MOX kinetics ...is a complex function of CH₄ and oxygen (O₂) concentrations. While MOX activity is usually proportional to the concentration of CH₄ itself, the effects of O₂ have been more conflicting, with maximum MOX rates often restricted to low O₂ concentrations. Despite the complexity involved, MOX kinetics are often modelled as monotonic positive functions of both CH₄ and O₂ concentrations. We conducted a series of incubation experiments using natural and unamended water samples obtained from multiple depths in northern temperate lakes that vary widely and independently in their CH₄ and O₂ concentrations. Our results showed the expected positive effect of CH₄ concentration and temperature but also demonstrated the strong inhibitory effects of O₂ at high concentration. We then developed a general model describing the kinetics of MOX, simultaneously integrating the effects of CH₄ concentration, temperature as well as the non-linear effect O₂ on MOX activity. The model revealed an overall temperature dependency (activation energy = 0.49 ± 0.06 eV) much lower than reported for methanogenesis and an optimal O₂ level around 15 µmol O₂ L⁻¹ where maximum MOX activity occurs, regardless of CH₄ concentration and temperature. We further show that ignoring the inhibitory effect of O₂ can lead to significant bias in calculating the expected MOX rates in different portions of the water column.
With some advances in modern medicine (such as cancer chemotherapy, broad exposure to antibiotics, and immunosuppression), the incidence of opportunistic fungal pathogens such as Candida albicans has ...increased. Cases of drug resistance among these pathogens have become more frequent, requiring the development of new drugs and a better understanding of the targeted enzymes. Sterol 14α-demethylase (CYP51) is a cytochrome P450 enzyme required for biosynthesis of sterols in eukaryotic cells and is the major target of clinical drugs for managing fungal pathogens, but some of the CYP51 key features important for rational drug design have remained obscure. We report the catalytic properties, ligand-binding profiles, and inhibition of enzymatic activity of C. albicans CYP51 by clinical antifungal drugs that are used systemically (fluconazole, voriconazole, ketoconazole, itraconazole, and posaconazole) and topically (miconazole and clotrimazole) and by a tetrazole-based drug candidate, VT-1161 (oteseconazole: (R)-2-(2,4-difluorophenyl)-1,1-difluoro-3-(1H-tetrazol-1-yl)-1-(5-(4-(2,2,2-trifluoroethoxy)phenyl)pyridin-2-yl)propan-2-ol). Among the compounds tested, the first-line drug fluconazole was the weakest inhibitor, whereas posaconazole and VT-1161 were the strongest CYP51 inhibitors. We determined the X-ray structures of C. albicans CYP51 complexes with posaconazole and VT-1161, providing a molecular mechanism for the potencies of these drugs, including the activity of VT-1161 against Candida krusei and Candida glabrata, pathogens that are intrinsically resistant to fluconazole. Our comparative structural analysis outlines phylum-specific CYP51 features that could direct future rational development of more efficient broad-spectrum antifungals.
Mechanochemistry offers exciting opportunities for molecular-level engineering of stress-responsive properties of polymers. Reactive sites, sometimes called mechanophores, have been reported to ...increase the material toughness, to make the material mechanochromic or optically healable. Here we show that macrocyclic cinnamate dimers combine these productive stress-responsive modes. The highly thermally stable dimers dissociate on the sub-second timescale when subject to a stretching force of 1-2 nN (depending on isomer). Stretching a polymer of the dimers above this force more than doubles its contour length and increases the strain energy that the chain absorbs before fragmenting by at least 600 kcal per mole of monomer. The dissociation produces a chromophore and dimers are reformed upon irradiation, thus allowing optical healing of mechanically degraded parts of the material. The mechanochemical kinetics, single-chain extensibility, toughness and potentially optical properties of the dissociation products are tunable by synthetic modifications.
•Additions of TMOs can accelerate 5AT pyrolysis and combustion processes.•Catalytic effects of TMOs on 5AT perform on polyaddition and ring-opening reaction.•Thermal pyrolysis mechanisms of 5AT ...without and with TMOs are proposed.•Reaction kinetic models for 5AT are investigated by model-fitting method.•Logarithm of pre-exponential factor shows good linearity with activation energy.
The employment of TMOs as catalyst has been widely popularized in thermal decomposition and combustion process, especially in propellants and explosives application areas. The focus of this study is on investigating catalytic effects of Fe2O3, CuO, and NiO nanoparticles on thermal decomposition mechanism and kinetics behavior of 5-Amino-1H-Tetrazole (5AT), one typical energetic material. Experimental result reveals that thermal decomposition process of 5AT can be simplified from three steps to two steps with the additions of above TMOs. Thermal decomposition mechanisms of 5AT with and without TMOs are deduced by TG-FTIR-MS analysis. Results indicate that the interaction between TMOs and dissociation products shows the catalytic effect together with the variation of production phase. Both model-free and model-fitting methods are employed to evaluate thermal kinetics of catalyzed 5AT. During low temperature reaction range (below 300 °C), no obvious change is observed in activation energies or mastering reaction models (F3 model). Conversely, catalytic effect of TMO is discovered mainly during high temperature range (above 300 °C), particularly during the polyaddition reaction of N-containing heterocycle and the ring-opening reaction of melem. The results of this study suggests that introducing TMOs nanostructure as catalysts into 5AT is a promising way to accelerate its combustion process in gas generation and propellant areas.
Typically induced by the mechanical processing of powders in ball mills, mechanochemical transformations are considered to result from the application of mechanical force to solid reactants. However, ...the undeniable deep connection between the dynamic compaction of powders during impacts and the overall transformation degree has yet to be disclosed. In the present work, we show that the square planar bis(dibenzoylmethanato)NiII coordination compound undergoes trimerization when its powder experiences even a single ball impact. Based on systematic experiments with individual ball impacts and analysis by Raman spectroscopy, we provide here quantitative mapping of the transformation in the powder compact and deduce bulk reaction kinetics from multiple individual impacts.
A single ball drop on a thin layer of loose bis(dibenzoylmethanato)NiII powders induces a partial trimerization reaction as a result of the severe mechanical deformation accompanying the formation of the powder compact. Repeated ball drops on the same powder compact result in an approximately linear increase of the trimer amount.
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•Nanocomposites show exceptional capability for antibiotic adsorption from aqueous media.•Adsorption depends on nanocomposite dosage, antibiotic levels, pH, contact time, and ...temperature.•The key mechanisms are hydrogen bonding, π-π interactions, and electrostatic interactions.•Thermodynamics shows adsorption processes are mostly spontaneous and exothermic.•Pseudo-second-order and Langmuir models best describe the adsorption kinetics and isotherms, respectively.•Identified gaps emphasize the need for further research to address issues of practicality and sustainability.
The increasing presence of antibiotics in aquatic environments necessitates the development of effective remediation strategies. This review comprehensively explores the potential of nanocomposites for antibiotic adsorption. Nanocomposites demonstrate superior performance in antibiotic removal, attributed to their unique properties arising from the combined advantages of the individual components of the composite. The review discussed the factors influencing the adsorption process, encompassing characteristics of both antibiotics and nanocomposites. Mechanisms, kinetics, and equilibrium isotherms were meticulously examined to elucidate the fundamental principles governing antibiotic adsorption. The review identified the dominant mechanisms of the process to be hydrogen bonding, π-π interactions, and electrostatic interactions. Notably, pseudo-second-order and Langmuir models were the most prevalent fit for adsorption kinetics and isotherms, respectively. The importance of thermodynamics in assessing process feasibility was emphasized, with reported data suggesting the spontaneous and exothermic nature of most adsorption processes. Additionally, the review explores the application of computer-aided modeling for optimizing adsorption efficiency. Finally, significant knowledge gaps were identified, and future research directions were highlighted. Ultimately, the adsorption of antibiotics by nanocomposites shows great promise, providing a long-term and practical solution to antibiotics contamination in aqueous environments. However, for nanocomposites to fully realize their potential in addressing the escalating problem of antibiotic contamination, more research and development in this field are essential.
Lipoprotein (a) Lp(a) is characterized by apolipoprotein (a) apo(a) covalently bound to apolipoprotein B 100. It was described in human plasma by Berg et al. in 1963 and the gene encoding apo(a) ...(LPA) was cloned in 1987 by Lawn and colleagues. Epidemiologic and genetic studies demonstrate that increases in Lp(a) plasma levels increase the risk of atherosclerotic cardiovascular disease. Novel Lp(a) lowering treatments highlight the need to understand the regulation of plasma levels of this atherogenic lipoprotein. Despite years of research, significant uncertainty remains about the assembly, secretion, and clearance of Lp(a). Specifically, there is ongoing controversy about where apo(a) and apoB-100 bind to form Lp(a); which apoB-100 lipoproteins bind to apo(a) to create Lp(a); whether binding of apo(a) is reversible, allowing apo(a) to bind to more than one apoB-100 lipoprotein during its lifespan in the circulation; and how Lp(a) or apo(a) leave the circulation. In this review, we highlight past and recent data from stable isotope studies of Lp(a) metabolism, highlighting the critical metabolic uncertainties that exist. We present kinetic models to describe results of published studies using stable isotopes and suggest what future studies are required to improve our understanding of Lp(a) metabolism.
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