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Analytical Techniques for Corrosion-Related Characterization of Graphene and Graphene-Based Nanocomposite Coatings
Published in Hatem M.A. Amin, Ahmed Galal, Corrosion Protection of Metals and Alloys Using Graphene and Biopolymer Based Nanocomposites, 2021
Saman Hosseinpour, Ali Davoodi, Arash Sedighi, Faeze Tofighi
Per a simplified definition, corrosion is the tendency of a metal to convert into metal oxide deteriorating the performance of the metal surface. The corrosion rate, in addition to the type of metal, thus depends on the environmental factors, temperature, and mechanical forces involved. Moreover, the electrochemical interactions between different parts of a metallic substrate and also its shape may influence its local corrosion rate. Protective coatings are among the best ways to prevent the corrosion of metals in the industry. These coatings include metallic or alloy based organic layers, silanes, conductive polymers, oxide layers, and even thiol-based, selenol-based or carboxylic acid-based monolayers [1–5]. Nevertheless, scratching or cracking of coatings and other imperfections in protective coatings are among the phenomena that may arise from the difference between the substrates, affecting the corrosion resistance properties of the coating/metal system [2, 6]. This issue is especially common in the thick protective layers.
Site-Specific Antibody Conjugation for ADC and Beyond
Published in Raj Bawa, János Szebeni, Thomas J. Webster, Gerald F. Audette, Immune Aspects of Biopharmaceuticals and Nanomedicines, 2019
The ADC was also site-specifically generated using selenocysteine (Sec) residues engineered at the C-terminus of the antibody with iodoacetamide containing monomethyl auristatin F (MMAF) [41]. In eukaryotes, Sec is encoded by the stop codon UGA, and its translational incorporation requires the presence of a Sec incorporation sequence (SECIS) in the UTR of the mRNA. Since the selenol group of Sec is more nucleophilic than the thiol group of cysteine, the antibody was conjugated under mildly acidic and reducing conditions without the antibody re-oxidation required for THIOMAB conjugation. The ADC showed strong antitumor activities in vitro and in vivo. Significant tumor growth inhibition and regression were observed for the anti-HER2 scFv-Fc-Sec conjugate. Four of the five mice treated with the ADC at a high dose were tumor free at six weeks after the last treatment.
Se, 34]
Published in Alina Kabata-Pendias, Barbara Szteke, Trace Elements in Abiotic and Biotic Environments, 2015
Alina Kabata-Pendias, Barbara Szteke
The nutritionally essential functions of Se appear to be discharged by some 25 selenoproteins. The specific selenoproteins include glutathione peroxidases (it is a constituent element of the entire defense system that protects the living organism from the harmful action of free radicals), thioredoxin reductases, 5-iodothyronine deiodinases, selenoprotein P, and others. Many forms of Se (including selenite, selenate, selenocysteine, and selenomethionine) are metabolized to hydrogen selenide. While the latter metabolite is the obligate precursor to the formation of selenocysteine in the specific selenoproteins, it can also be serially methylated (to methyl selenol, dimethylselenide, and trimethylselenonium ion) or converted to a selenosugar, and excreted.
Understanding selenium metabolism in plants and its role as a beneficial element
Published in Critical Reviews in Environmental Science and Technology, 2019
Reshu Chauhan, Surabhi Awasthi, Sudhakar Srivastava, Sanjay Dwivedi, Elizabeth A. H. Pilon-Smits, Om P. Dhankher, Rudra D. Tripathi
Selenium is a metalloid that lies between sulfur and tellurium in VIA group and between arsenic and bromine in 4th period of periodic table. Selenium shows chemical similarity with S in respect to bond energies, ionization potentials, atomic size, electronegativities and electron affinities. However, Se exists as reduced quadrivalent form while S in oxidized quadrivalent form; this is the major difference between Se and S (Tinggi, 2003). At physiological pH, selenium compounds (selenol) dissociate readily, which is important for its role in catalytic reactions (Tinggi, 2003). Selenium can exist in various oxidation states that allow it to form selenoamino acids and organoselenium compounds (Tinggi, 2003). The most common valence states of Se are −2, 0, +2, +4 and +6 (Table 1). The predominant available forms of Se to plants are inorganic, i.e. selenite (SeIV) and selenate (SeVI) (Schiavon & Pilon-Smits, 2017; White et al., 2004).
Quantum chemical study of tautomeric equilibriums, intramolecular hydrogen bonds, and π-electron delocalization in the first singlet and triplet excited states of 2-selenoformyl-3-thioxo-propionaldehyde
Published in Journal of Sulfur Chemistry, 2023
Ramin Rafat, Ebrahim Nakhaei, Farshid Zargari, Faezeh Gorgichi, Alireza Nowroozi
Tautomeric energy changes (ΔETE) and activation energies (Ea) of keto⇄enol, thione⇄thiol, and selone⇄selenol equilibriums of STP were calculated and shown in Table 2. Unlike acetaldehyde, the calculated ΔETE of all of the mentioned phenomena is completely negative, which can be probably assigned to the presence of π-electron delocalization. Obviously, for eliminating the stabilization effects of IMHB, the open forms of tautomers without hydrogen bonding have been considered. These values show that the open form of excited states of thiol tautomers at all of the computational levels is extra-stable than the non-hydrogen bonded forms of enol and selenol. In other words, the thiol conformers are thermodynamically preferred over the other forms. For example, the ΔETE values of keto⇄enol, thione⇄thiol, and selone⇄selenol tautomeric equilibriums in the triplet excited state with the TD-DFT method are about −36.98, −64.85, and −57.57 kJ/mol, respectively. In addition, the forward and reverse activation energies of the mentioned equilibriums also exist in Table 4. These values can give us important information about the preference of tautomers from a kinetic viewpoint. The energetic stability of thione⇄thiol equilibrium is more than the enol and selenol ones. For instance, the amounts of forward activation energies of keto⇄enol, thione⇄thiol, and selone⇄selenol tautomeric equilibriums at TD-DFT in triplet state are about 279.63, 249.16, and 257.26 kJ/mol, respectively. By evaluating the amounts of ΔETE and activation energies, we concluded that the thione⇄thiol tautomeric equilibrium is completely preferred to the other process, from both thermodynamic and kinetic viewpoints. These results are completely in agreement with the relative energies.