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Related Topics I: Charge-Transfer Complexes in Biological Systems
Published in Jean-Pierre Farges, Organic Conductors, 2022
Vivian C. Flores, Hendrik Keyzer, Cissy Varkey-Johnson, Karen Leslie Young
The blue starch iodine complex has been used from time immemorial as an indicator in aqueous iodometric titrations; water is required for development of the blue color. The color sensitivity is decreased with increasing temperature and also with increasing concentration of ethanol [134], A1-though one might imagine this to be evidence for a charge-transfer complex, Structures of lecithin, cholestanol (cholesterol derivative), and chlorophyll b.Bersohn and Isenberg [135] suggest that these adducts involve covalent bonding of a metallic kind. This complex is formed by inclusion of I3− in the spiral starch molecule with a stoichiometry of six glucose units per I3− With amylose a green-to-blue I2 complex is formed in which one glucose unit traps an I3− Amylopectin, a branched-chain molecule, reacts with one I3− molecule per spiral to form a reddish-purple adduct [136]. While steroids are not carbohydrates, oxygen-bearing steroid dimer triiodide ion complexes are known, for example, in which the I3− bridges the two steroids via keto-oxygens [137]. A similar mechanism may operate in the starch complexes.
Expression and characterization of cholesterol oxidase with high thermal and pH stability from Janthinobacterium agaricidamnosum
Published in Preparative Biochemistry & Biotechnology, 2023
Noriyuki Doukyu, Yuuki Ikehata, Taichi Sasaki
The ChoJ oxidized various 3β-hydroxysteroids (Table 4). It oxidized cholesterol and β-cholestanol at high rates. On the other hand, the oxidation rates of sterols with side-chain structures different from that of cholesterol, such as β-sitosterol, β-stigmasterol, ergosterol, pregnenolone, and dehydroepiandrosterone, were lower than those of cholesterol and β-cholestanol. The Km, Vmax, and kcat values for cholesterol were 156 ± 8 μM, 13.7 ± 0.4 μmol/min/mg protein, and 14.4 ± 0.4 s−1, respectively (Table 5). The kcat value of ChoJ was the highest after that of P. aeruginosa PAO157 and was 24-, 2.1-, 1.9-, and 1.3-fold higher than those of R. erythropolis (ChoRII), R. erythropolis (ChoRI), B. cepacia ST-200, and Chromobacterium sp. DS-1, respectively. Although the Km value of ChoJ was the highest among the COXases shown in Table 5, the catalytic efficiency kcat/Km of ChoJ was similar to that of B. cepacia ST-200, which is commercially available from Kikkoman Biochemifa Company (Tokyo, Japan).
Assessing the presence of endocrine disruptors and markers of anthropogenic activity in a water supply system in northeastern Brazil
Published in Journal of Environmental Science and Health, Part A, 2019
Isabella Ferreira Nascimento Maynard, Eliane Bezerra Cavalcanti, Larissa Limeira da Silva, Elâine Arantes Jardim Martins, Maria Aparecida Faustino Pires, Marcelo Lima de Barros, Eni Cardoso, Maria Nogueira Marques
Our results evidence values lower than some results in the literature. Otomo[20] observed 14 organic compounds in Guarapiranga dam, São Paulo State. He recorded maximum concentrations of 1.06 μg L−1 and 12.9 μg L−1 for bisphenol A and dibutyl phthalate, respectively. DEs recorded cholestanol and cholesterol at 0.11 μg L−1 and 12.81 μg L−1, respectively, based on the human-activity tracer class.