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Enzyme Kinetics and Drugs as Enzyme Inhibitors
Published in Peter Grunwald, Pharmaceutical Biocatalysis, 2019
The term “enzyme kinetics” is in so far somewhat misleading as one might draw the conclusion from it that the basic principles of chemical kinetics are not valid in this area, which is of course not the case. Reactions catalyzed by bioactive material likewise depend on parameters like concentration, temperature, etc.—the peculiarity is that during the reaction an intermediate is involved which is in equilibrium with the reactants. As it is characteristic for catalysts, enzymes catalyze a reaction in both directions, which is of considerable importance for organic synthesis. Irrespective of that, a treatment of enzyme kinetics is based on the interaction between a macromolecule and a small ligand that normally is the substrate but which can also be an inhibitor, an activator, a co-factor, etc. Because of the usually large differences in particle size between enzymes (10 to 100 nm) and substrate molecules (e.g., ~0.7 nm for glucose), enzyme kinetics marks the transition between homogeneous and heterogeneous catalysis and is therefore sometimes named micro-heterogeneous catalysis. As in case of heterogeneous catalysis, enzyme-catalyzed reactions show the phenomenon of substrate saturation.
Biodiesel Production from Microalgal Biomass
Published in Gokare A. Ravishankar, Ranga Rao Ambati, Handbook of Algal Technologies and Phytochemicals, 2019
Srijoni Banerjee, Debabrata Das
Nanoparticles play a significant role as catalysts for the production of biodiesel, owing to their higher catalytic activity, large specific surface area, high resistance to saponification reaction and good rigidity. A higher level of biodiesel yield was obtained using nanoparticles as catalyst. Efficient and recyclable heterogeneous catalysts like metal oxide catalysts (e.g., ZnO), metal supported by metal oxide catalysts (e.g., Au–ZnO), alloy (e.g., Cu–Co) and metal oxide supported by metal oxide (e.g., KF–CaO–Fe3O4) can be used for the transesterification process. Enzymatic catalysis with the use of lipases is also possible (Azean and Yilmaz 2012), however, its costs are very high (Thanh et al. 2012).
Kinetics Part 2 Application of Rate Laws and Rate Variables to Reaction Mechanisms
Published in Patrick E. McMahon, Rosemary F. McMahon, Bohdan B. Khomtchouk, Survival Guide to General Chemistry, 2019
Patrick E. McMahon, Rosemary F. McMahon, Bohdan B. Khomtchouk
A catalyst is an agent that increases the rate of a chemical reaction without itself being net consumed in the reaction. The catalyst may act without undergoing observable change in chemical form. This is typical of heterogeneous catalysis; the catalyst and reactant(s) are in different phases. This is the dominant technology used in the chemical industry. Examples are solid metal surfaces catalyzing reactions of liquid, solution, or gaseous reactants.
Synthesis of benzo[a]furo[2, 3-c]phenazine derivatives through an efficient, rapid and via microwave irradiation under solvent-free conditions catalyzed by H3PW12O40@Fe3O4-ZnO for high-performance removal of methylene blue
Published in Artificial Cells, Nanomedicine, and Biotechnology, 2021
Milad Taheri, Razieh Mohebat, Mohammad Hossein Moslemin
Recently, semiconductor heterogeneous photocatalysts such as TiO2 and ZnO have attracted a lot of attention due to their excellent performance in destroying organic compounds and purifying water. Among them, pure nano-ZnO has important research and application value because of its bandgap width of 3.2 eV [11,12]. Also, due to the recyclability of the catalyst, Fe3O4 has been considered by many researchers as a ferromagnetic material due to its good ability [13,14]. Based on the above study, we completed the effective combination of ZnO and Fe3O4–ZnO and designed an H3PW12O40@Fe3O4–ZnO core-shell photocatalyst with magnetic separation capability. Core-shell nanoparticles are used for medical applications, and due to their high stability, this magnetic nanoparticle can be useful for hyperthermia magnetic therapy (MHT) for the treatment of cancer [15,16]. Furthermore, nanomaterial applications as a heterogeneous catalyst in place of homogeneous catalysts in MCRs make the process greener due to easy handling, non-corrosiveness, high surface area, surface modification ability, excellent thermal and chemical stability, simple work-up procedures, environmentally benign nature, reusability, low cost and ease of synthesis and isolation [17,18]. Among them, non-toxic ZnO and ZnO nanoparticles catalyzed organic processes are often considered to follow the principles of green chemistry, that is, these catalyzed processes consume a minimum of energy and reagents or auxiliaries and minimize waste [19].
Photo-Fenton oxidative of pharmaceutical wastewater containing meropenem and ceftriaxone antibiotics: influential factors, feasibility, and biodegradability studies
Published in Toxin Reviews, 2020
Bahareh Kordestani, Afshin Takdastan, Reza Jalilzadeh Yengejeh, Abdol Kazem Neisi
Recently, the application of heterogeneous catalysts in Fenton processes has been mostly attracted the attention of environmentalists. However, heterogeneous Fenton oxidation suffers from some limitations including, huge cost of catalyst, consumption of high amount of chemicals, high costs of required energy and significant production of waste materials. Although homogeneous Fenton process has shown a considerable performance, its low efficiency in the recovery of Fe made researchers to modify this approach (Ahmadi et al. 2017b). On the other hand, many studies have demonstrated that the application of light (<580 nm) is an efficient and promising method for enhancement of Fe2+ regeneration through Fe3+ photolysis, know as photo-Fenton reaction (Kakavandi et al. 2016). Herein, UV light can play an important role in improvement of the degradation efficiency of organic pollutants thereby either direct or indirect production of reactive oxidizing species, as described in Equations 12 and 13 (Ferkous et al. 2017, Chakma et al. 2017).
The first and low cost copper Schiff base/manganese oxide bio nanocomposite from unwanted plants as a robust industrial catalyst
Published in Artificial Cells, Nanomedicine, and Biotechnology, 2020
Atena Naeimi, Sedighe Abbasspour, Seyedeh Atekeh Torabizadeh
Oxidation reaction is one of the most important reactions in pharmaceutical industries [30]. The safety of oxidation systems in large scale can influence on the hesitation to employ. Fuel, energy and oxidant are three factors in reactors for performing oxidation reactions in industry [31]. Hence, green strategies attract so much attention as economical and environmental point of view. Oxidation of alcohols to aldehydes, esters and carboxylic acids, and ketones are one of the most essential chemical processes in both academic and industrial research, because alcohols can transfer to valuable products for pharmaceuticals, dyestuffs, agrochemicals and fragrances industries [31–34]. Many applied homogeneous catalysts for these reactions created many challenges from the environmental point of view. Hence, increasing efforts have been devoted in developing heterogeneous catalysts. Recently, metal matrix nanocomposites including metal oxides or/and nano transition metal oxide could replace instead of heterogeneous catalyst. Particularly and ideally in aqueous solution, H2O2 is greatly attractive for releasing active oxidative species and producing water as the only by-product. In this context, employing nano metal oxides along with nano-transition metal complex to fabricate efficient catalysts for alcohols oxidation with green oxidant is highly desirable [35].