Glove Selection for Work with Acrylates Including Those Cured by Ultraviolet, Visible Light, or Electron Beam
Robert N. Phalen, Howard I. Maibach in Protective Gloves for Occupational Use, 2023
In today's industrial practice, some five to ten different families of acrylate oligomers (molecules with few repeating units) are commercially available. The most widely used families are commonly referred to as epoxy acrylates, urethane acrylates, and polyester acrylates. They are typically manufactured in a relatively short synthetic route and sold as such or diluted in acrylate monomer for easier handling. As for most industrial applications, synthesis does not normally include washing, distilling, or other purification steps; these chemicals are rather complex mixtures of molecules with various molecular weights. Moreover, the final product typically contains lesser amounts of residual catalysts (all kinds of industrial catalysts are in use for their manufacture) and one or more inhibitors. Inhibitors are used to prevent polymerization during transport, storage, and the manufacture of industrial intermediates such as inks, coatings, or adhesives. The inhibitors are typically phenolic molecules, of which the two most widely used are hydroquinone and p-methoxyphenol.
Enzyme Kinetics and Drugs as Enzyme Inhibitors
Peter Grunwald in 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.
Underreporting and Reporting Delays
Leonhard Held, Niel Hens, Philip O’Neill, Jacco Wallinga in Handbook of Infectious Disease Data Analysis, 2019
Catalytic models are inspired by chemical reactions whose rates are speeded by the use of a catalyst. The catalyst in our context is the conditions that allow a certain infection to develop and spread at a certain rate. Knowing this rate and the conditions around it allows estimation of the proportion of underreporting. Muench (1959) described the simplest model that can explain infectious disease data as one that should contain one constant representing the rate at which the disease is acquired and one representing the rate at which it is lost. Muench (1959) constructed a catalytic model that fits upon bilharziasis transmission rates. Most existing catalytic models considered for explaining disease paths are deterministic. Presently, it is advised to expand deterministic models to include random factors. More recent probability models introduce an error term that explains natural phenomenon more realistically as will be seen in what follows.
Removal of malathion insecticide from aqueous solution by the integration of persulfate process and magnetite nanoparticles loaded on carbon (Fe3O4@CNT) in the presence of ultraviolet radiation
Published in Toxin Reviews, 2022
Malektaj Eskandari makvand, Sima Sabzalipour, Mahboobeh Cheraghia, Neda Orak
Iron is a safe, non-toxic, and inexpensive element. It is noteworthy that the iron residues must be separated into inhomogeneous forms (Fe2+ or Fe3+) and the use of those solvents requires more processing. Nonetheless, inhomogeneous catalysis could be reused, which is an extraordinary advantage compared to the homogeneous form of this substance (Zhu et al.2013). Magnetite (Fe3O4) or divalent and trivalent iron oxide is widely employed as a catalyst in the photocatalysts and Fenton-dependent processes (Guo et al.2010, Huang et al. 2012, Mishra and Chun 2015), which is owing to the high ability of this substance to decompose the hydrogen peroxide and convert it to hydroxyl radical. Moreover, Fe3O4 has shown good stability in the photocatalysis process (Mishra and Chun 2015). In this regard, some superficial reactions of Fe3O4 with persulfate would lead to producing the sulfate radicals based on Equations (2–5) (Ji et al.2013, Oh et al.2015).
Inactivation of the superoxide dismutase by malondialdehyde in the nonalcoholic fatty liver disease: a combined molecular docking approach to clinical studies
Published in Archives of Physiology and Biochemistry, 2021
Arash Arya, Nahid Azarmehr, Mahboubeh Mansourian, Amir Hossein Doustimotlagh
In a structure-based approach, the molecular docking was done to further characterize the potential binding mechanism between MDA and antioxidant SOD enzyme. The importance of cell defense by the SOD enzyme against oxidative damage of ROS has been shown in all aerobic organisms (Perry et al. 2010). In this study, we are focusing on SOD1. Optimized structure of ligand (herein MDA) was docked into the active site of human cytoplasmic Cu/Zn SOD (SOD1). The three-dimensional (3 D) X-ray crystal structure was gotten from the RCSB Protein Data Bank with 2C9V PDB code for SOD1 at resolution 1.07 Å (Strange et al. 2006). The SOD1 is a dimer with identical subunits; each subunit consists of shaped funnel di nuclear metal cluster bearing Cu/Zn ions in active site. For their activation, catalytic metal ions are required (Rakhit et al. 2002). For preparation of enzymes molecules, water molecules were removed. The 3 D structure of MDA as a ligand was drawn and optimized to interact with related enzyme as previously mentioned (Fassihi et al. 2012; Mansourian et al.2013).
Degradation of phosalone by silver ion catalytic hydrolysis
Published in Toxicology Mechanisms and Methods, 2021
Jalal Hassan, Roya Kamrani, Hadi Tabarraei, Fardad Pirri, Mohammad Rezaian Nojani, A. Wallace Hayes
One necessary condition for a proposed reaction mechanism to be correct is that it must account for the overall kinetic behavior of the reaction—in particular, the dependence of the reaction rate on the reactant concentrations. For any reaction mechanism, it is possible to propose equations for the rate of each step in terms of the reactant concentration and then to solve the equations for the overall rate. If a reaction rate depends on a single reactant and the value of the exponent is one, then the reaction is said to be first order and the concentration of a reactant remains constant (because it is either a catalyst or it is in great excess with respect to the other reactants), its concentration can be included in the rate constant, obtaining a pseudo-first-order (or occasionally pseudo-second-order) rate equation.
Related Knowledge Centers
- Chemical Reaction
- Effervescence
- Enzyme
- Heterogeneous Catalysis
- Hydrogen Peroxide
- Oxygen
- Reaction Rate
- Reaction Intermediate
- Homogeneous Catalysis
- Elizabeth Fulhame