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排序方式: 共有116条查询结果,搜索用时 15 毫秒
111.
Benjamin Aberle Daniel Kowalczyk Simon Massini Alexander-N. Egler-Kemmerer Dr. Sebastian Gergel Prof. Dr. Stephan C. Hammer Prof. Dr. Bernhard Hauer 《Angewandte Chemie (International ed. in English)》2023,62(26):e202306111
Terpenoids are built from isoprene building blocks and have numerous biological functions. Selective late-stage modification of their carbon scaffold has the potential to optimize or transform their biological activities. However, the synthesis of terpenoids with a non-natural carbon scaffold is often a challenging endeavor because of the complexity of these molecules. Herein we report the identification and engineering of (S)-adenosyl-l -methionine-dependent sterol methyltransferases for selective C-methylation of linear terpenoids. The engineered enzyme catalyzes selective methylation of unactivated alkenes in mono-, sesqui- and diterpenoids to produce C11, C16 and C21 derivatives. Preparative conversion and product isolation reveals that this biocatalyst performs C−C bond formation with high chemo- and regioselectivity. The alkene methylation most likely proceeds via a carbocation intermediate and regioselective deprotonation. This method opens new avenues for modifying the carbon scaffold of alkenes in general and terpenoids in particular. 相似文献
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Back BB Baker MD Ballintijn M Barton DS Betts RR Bickley AA Bindel R Budzanowski A Busza W Carroll A Chai Z Decowski MP García E Gburek T George N Gulbrandsen K Gushue S Halliwell C Hamblen J Hauer M Heintzelman GA Henderson C Hofman DJ Hollis RS Hołyński R Holzman B Iordanova A Johnson E Kane JL Katzy J Khan N Kucewicz W Kulinich P Kuo CM Lin WT Manly S McLeod D Mignerey AC Nouicer R Olszewski A Pak R Park IC Pernegger H Reed C Remsberg LP Reuter M Roland C Roland G Rosenberg L Sagerer J 《Physical review letters》2006,97(1):012301
We report on measurements of directed flow as a function of pseudorapidity in Au + Au collisions at energies of square root of SNN = 19.6, 62.4, 130 and 200 GeV as measured by the PHOBOS detector at the BNL Relativistic Heavy Ion Collider. These results are particularly valuable because of the extensive, continuous pseudorapidity coverage of the PHOBOS detector. There is no significant indication of structure near midrapidity and the data surprisingly exhibit extended longitudinal scaling similar to that seen for elliptic flow and charged particle pseudorapidity density. 相似文献
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Dr. Andreas Schneider Dr. Christian Curado Thomas B. Lystbaek Prof. Sílvia Osuna Prof. Bernhard Hauer 《Angewandte Chemie (International ed. in English)》2023,62(22):e202305546
Terpene cyclases offer enormous synthetic potential, given their unique ability to forge complex hydrocarbon scaffolds from achiral precursors within a single cationic rearrangement cascade. Harnessing their synthetic power, however, has proved to be challenging owing to their generally low catalytic performance. In this study, we unveiled the catalytic potential of the squalene-hopene cyclase (SHC) by harnessing its structure and dynamics. First, we synergistically tailored the active site and entrance tunnel of the enzyme to generate a 397-fold improved (−)-ambroxide synthase. Our computational investigations explain how the introduced mutations work in concert to improve substrate acquisition, flow, and chaperoning. Kinetics, however, showed terpene-induced inactivation of the membrane-bound SHC to be the major turnover limitation in vivo. Merging this insight with the improved and stereoselective catalysis of the enzyme, we applied a feeding strategy to exceed 105 total turnovers. We believe that our results may bridge the gap for broader application of SHCs in synthetic chemistry. 相似文献
116.
has been studied by using a complete active space MCSCF wave function generated by distributing eight electrons among eight orbitals. 相似文献