1075-49-6Relevant articles and documents
Structural insights into the role of the acid-alcohol pair of residues required for dioxygen activation in cytochrome P450 enzymes
Coleman, Tom,Stok, Jeanette E.,Podgorski, Matthew N.,Bruning, John B.,De Voss, James J.,Bell, Stephen G.
, p. 583 - 596 (2020)
The cytochrome P450 heme monooxygenases commonly use an acid-alcohol pair of residues, within the I-helix, to activate iron-bound dioxygen. This work aims to clarify conflicting reports on the importance of the alcohol functionality in this process. Mutants of the P450, CYP199A4 (CYP199A4D251N and CYP199A4T252A), were prepared, characterised and their crystal structures were solved. The acid residue of CYP199A4 is not part of a salt bridge network, a key feature of paradigmatic model system P450cam. Instead, there is a direct proton delivery network, via a chain of water molecules, extending to the surface. Nevertheless, CYP199A4D251N dramatically reduced the activity of the enzyme consistent with a role in proton delivery. CYP199A4T252A decreased the coupling efficiency of the enzyme with a concomitant increase in the hydrogen peroxide uncoupling pathway. However, the effect of this mutation was much less pronounced than reported with P450cam. Its crystal structures revealed fewer changes at the I-helix, compared to the P450cam system. The structural changes observed within the I-helix of P450cam during oxygen activation do not seem to be required in this P450. These differences are due to the presence of a second threonine residue at position 253, which is absent in P450cam. This threonine forms part of the hydrogen bonding network, resulting in subtle structural changes and is also present across the majority of the P450 superfamily. Overall, the results suggest that while the acid-alcohol pair is important for dioxygen activation this process and the method of proton delivery can differ across P450s. Graphic abstract[Figure not available: see fulltext.].
Precision polyelectrolytes
Srichan, Sansanee,Oswald, Laurence,Zamfir, Mirela,Lutz, Jean-Franois
, p. 1517 - 1519 (2012)
Charged macromolecules with controlled microstructures were prepared. Well-defined non-ionic precursors were first synthesized by sequence-controlled radical polymerization of tert-butyl 4-vinyl benzoate with various N-substituted maleimides. Afterwards, these macromolecules were hydrolyzed into polyanions.
Amphiphilic polymethacrylate- and polystyrene-based chemical delivery systems for damascones
Berthier, Damien,Trachsel, Alain,Fehr, Charles,Ouali, Lahoussine,Herrmann, Andreas
, p. 3089 - 3108 (2005)
Amphiphilic polystyrene- and polymethacrylate-based β-acyloxy ketones were investigated as potential delivery systems for the controlled release of damascones by retro-1,4-addition in applications of functional perfumery. A series of random copolymers being composed of the hydrophobic damascone-release unit and a second hydrophilic monomer were obtained by radical polymerization in organic solution by using 2,2-azobis[2-methylpropanenitrile] (AIBN) as the radical source (Schemes 2 and 3). A first evaluation of the polymer conjugates in acidic or alkaline buffered aqueous solution, and in the presence of a surfactant, showed that polymethacrylates and polystyrenes having a carboxylic acid function as hydrophilic group are particularly interesting for the targeted applications (Table 2). The release of δ-damascone (1) from polymers with poly(methacrylic acid) and poly(vinylbenzoic acid) comonomers in different stoichiometric ratios was thus followed over several days at pH 4, 7, and 9 by comparison of fluorescence probing, solvent extraction, and particle-size measurements (Tables 3 and 4). In acidic media, the polymers were found to be stable, and almost no δ-damascone (1) was released. In neutral or alkaline solution, where the carboxylic acid functions are deprotonated, the concentration of 1 increased over time. In the case of the polymethacrylates, the fluorescence probing experiments showed an increasing hydrophilicity of the polymer backbone with increasing fragrance release, whereas in the case of the polystyrene support, the hydrophilicity of the environment remained constant. These results suggest that the nature of the polymer backbone may have a stronger influence on the fragrance release than the ratio of hydrophilic and hydrophobic monomers in the polymer chain.
Cobalt-Catalyzed Reductive Carboxylation of Aryl Bromides with Carbon Dioxide
Hang, Wei,Yi, Yaping,Xi, Chanjuan
supporting information, p. 2337 - 2341 (2020/04/30)
Cobalt-catalyzed reductive carboxylation of aryl bromides with carbon dioxide has been developed. The reaction proceeded under one atm pressure of CO2 at 40 °C in the presence of cobalt iodide/2,2′-bipyridine catalysts and zinc dust as a reducing reagent. Various aryl bromides could be converted to the corresponding carboxylic acids in good to high yields. Preliminary mechanistic experiments ruled out intervention of intermediate organozinc species for carboxylation with CO2, thus suggesting a direct CO2 insertion into the corresponding ArCoBr species. (Figure presented.).
Manganese-Catalyzed N-Alkylation of Sulfonamides Using Alcohols
Reed-Berendt, Benjamin G.,Morrill, Louis C.
, p. 3715 - 3724 (2019/03/30)
An efficient manganese-catalyzed N-alkylation of sulfonamides has been developed. This borrowing hydrogen approach employs a well-defined and bench-stable Mn(I) PNP pincer precatalyst, allowing benzylic and simple primary aliphatic alcohols to be employed as alkylating agents. A diverse range of aryl and alkyl sulfonamides undergoes mono-N-alkylation in excellent isolated yields (32 examples, 85% average yield).
