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991.
992.
Linda Ofori Atta Dr. Zhi Zhou Prof. Dr. Gerard Roelfes 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2023,135(1):e202214191
Artificial enzymes utilizing the genetically encoded non-proteinogenic amino acid p-aminophenylalanine (pAF) as a catalytic residue are able to react with carbonyl compounds through an iminium ion mechanism to promote reactions that have no equivalent in nature. Herein, we report an in vivo biocatalytic cascade that is augmented with such an artificial enzyme-catalysed new-to-nature reaction. The artificial enzyme in this study is a pAF-containing evolved variant of the lactococcal multidrug-resistance regulator, designated LmrR_V15pAF_RMH, which efficiently converts benzaldehyde derivatives produced in vivo into the corresponding hydrazone products inside E. coli cells. These in vivo biocatalytic cascades comprising an artificial-enzyme-catalysed reaction are an important step towards achieving a hybrid metabolism. 相似文献
993.
Prof. Allan J. Canty Prof. Alireza Ariafard Prof. Gerard van Koten 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(62):15426-15433
Density functional theory computation indicates that bridge splitting of [PtIIR2(μ-SEt2)]2 proceeds by partial dissociation to form R2Pta(μ-SEt2)PtbR2(SEt2), followed by coordination of N-donor bromoarenes (L-Br) at Pta leading to release of PtbR2(SEt2), which reacts with a second molecule of L-Br, providing two molecules of PtR2(SEt2)(L-Br-N). For R=4-tolyl (Tol), L-Br=2,6-(pzCH2)2C6H3Br (pz=pyrazol-1-yl) and 2,6-(Me2NCH2)2C6H3Br, subsequent oxidative addition assisted by intramolecular N-donor coordination via PtIITol2(L-N,Br) and reductive elimination from PtIV intermediates gives mer-PtII(L-N,C,N)Br and Tol2. The strong σ-donor influence of Tol groups results in subtle differences in oxidative addition mechanisms when compared with related aryl halide oxidative addition to palladium(II) centres. For R=Me and L-Br=2,6-(pzCH2)2C6H3Br, a stable PtIV product, fac-PtIVMe2{2,6-(pzCH2)2C6H3-N,C,N)Br is predicted, as reported experimentally, acting as a model for undetected and unstable PtIVTol2{L-N,C,N}Br undergoing facile Tol2 reductive elimination. The mechanisms reported herein enable the synthesis of PtII pincer reagents with applications in materials and bio-organometallic chemistry. 相似文献
994.
995.
Carla Kirschbaum Dr. Essa M. Saied Kim Greis Dr. Eike Mucha Sandy Gewinner Dr. Wieland Schöllkopf Prof. Gerard Meijer Prof. Gert von Helden Dr. Berwyck L. J. Poad Prof. Stephen J. Blanksby Prof. Christoph Arenz Prof. Kevin Pagel 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(32):13740-13744
996.
The influence of ball to powder ratio and discontinous milling during ball milling of Fe0.75C0.25 elemental powder mixture is presented. The formation of Fe3C cementite, Hägg and ε carbides has been follwed by X-ray diffraction and Mössbauer Spectroscopy. Higher ball to powder ratios induce faster kinetics. Synthesized cementite has crystallite sizes 9 to 11 nm. 相似文献
997.
998.
Multilayers of cobalt and niobium have been deposited in ultra high vacuum, using two E-beams onto both corning glass and silicon wafers substrates kept at 20°C. These films were then ion mixed using Xe ions at 200, 300 and 400 keV. The dose was 3 × 1015 ions cm-2 in all cases. FMR and usual magnetization measurements were made to characterize the samples. Films mixed at 300 and 400 keV are homogeneous. FMR line width of 60 Oe and the simple spectra obtained lead us to conclude that these films are much more homogeneous than co-evaporated amorphous films of the same composition. 相似文献
999.
Eckhoff's conjecture for the Τ-Radon numbers r(Τ) of a convexity space. (X,C) says r(Τ) ≦ (r?1)(Τ?1)+1, with r = r(2). The main result of this note is that Eckhoff's conjecture is true in case ¦X¦ ≦ 2r and Τ = 3, i.e. each (2r?1)-set in a space with 2r?1 or 2r elements has a 3-Radon partition. 相似文献
1000.