排序方式: 共有66条查询结果,搜索用时 64 毫秒
41.
Dr. Federico Bertani Nicolò Riboni Prof. Federica Bianchi Dr. Giovanna Brancatelli Dr. Elizabeth S. Sterner Dr. Roberta Pinalli Prof. Silvano Geremia Prof. Timothy M. Swager Prof. Enrico Dalcanale 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(10):3312-3319
Two novel triptycene quinoxaline cavitands ( DiTriptyQxCav and MonoTriptyQxCav ) have been designed, synthesized, and applied in the supramolecular detection of benzene, toluene, ethylbenzene, and xylenes (BTEX) in air. The complexation properties of the two cavitands towards aromatics in the solid state are strengthened by the presence of the triptycene moieties at the upper rim of the tetraquinoxaline walls, promoting the confinement of the aromatic hydrocarbons within the cavity. The two cavitands were used as fiber coatings for solid‐phase microextraction (SPME) BTEX monitoring in air. The best performances in terms of enrichment factors, selectivity, and LOD (limit of detection) values were obtained by using the DiTriptyQxCav coating. The corresponding SPME fiber was successfully tested under real urban monitoring conditions, outperforming the commercial divinylbenzene–Carboxen–polydimethylsiloxane (DVB–CAR–PDMS) fiber in BTEX adsorption. 相似文献
42.
A new acylated neohesperoside derivative, 1-octyl-4'-isovaleroyl-neohesperoside (1), was isolated from Geranium purpureum Vill. (Geraniaceae) together with the known compounds quercetin-3-rutinoside and gallic acid. The identification of the isolated compounds was carried out by spectroscopic analysis including 1D- and 2D- NMR (1H, 13C, COSY, HSQC and HMBC) spectroscopy and ESI-TOF-MS. 相似文献
43.
E. Sterner 《BIT Numerical Mathematics》1997,37(1):164-178
The stationary Navier-Stokes equations are solved in 2D with semi-implicit Runge-Kutta schemes, where explicit time-integration
in the streamwise direction is combined with implicit integration in the body-normal direction. For model problems stability
restrictions and convergence properties are studied. Numerical experiments for the flow over a flat plate show that the number
of iterations for the semi-implicit schemes is almost independent of the Reynolds number. 相似文献
44.
Bernd Reisinger Natascha Kuzmanovic Patrick Löffler Prof. Dr. Rainer Merkl Prof. Dr. Burkhard König Prof. Dr. Reinhard Sterner 《Angewandte Chemie (International ed. in English)》2014,53(2):595-598
The activity of the metabolic branch‐point enzyme PriA from Mycobacterium tuberculosis (mtPriA) can be controlled reversibly by light. Two‐pronged inhibitors based on the dithienylethene scaffold were designed utilizing mtPriA’s natural rotational symmetry. Switching from the flexible, ring‐open to the rigid, ring‐closed isomer reduces inhibition activity by one order of magnitude. 相似文献
45.
Z-Ligustilide, a naturally occurring phthalide isolated from Ligusticum porteri, underwent Diels-Alder reactions with different dienophiles yielding novel tricyclic products with potentially interesting biological properties. Where selectivity was possible, the reactions performed showed regio- and stereoselectivity. The experimental results with ethyl acrylate were compared with the selectivity predicted by ab initio calculations. 相似文献
46.
47.
Carstensen L Sperl JM Bocola M List F Schmid FX Sterner R 《Journal of the American Chemical Society》2012,134(30):12786-12791
The (βα)(8)-barrel is among the most ancient, frequent, and versatile enzyme structures. It was proposed that modern (βα)(8)-barrel proteins have evolved from an ancestral (βα)(4)-half-barrel by gene duplication and fusion. We explored whether the mechanism of protein folding has remained conserved during this long-lasting evolutionary process. For this purpose, potential primordial (βα)(8)-barrel proteins were constructed by the duplication of a (βα)(4) element of a modern (βα)(8)-barrel protein, imidazole glycerol phosphate synthase (HisF), followed by the optimization of the initial construct. The symmetric variant Sym1 was less stable than HisF and its crystal structure showed disorder in the contact regions between the half-barrels. The next generation variant Sym2 was more stable than HisF, and the contact regions were well resolved. Remarkably, both artificial (βα)(8)-barrels show the same refolding mechanism as HisF and other modern (βα)(8)-barrel proteins. Early in folding, they all equilibrate rapidly with an off-pathway species. On the productive folding path, they form closely related intermediates and reach the folded state with almost identical rates. The high energy barrier that synchronizes folding is thus conserved. The strong differences in stability between these proteins develop only after this barrier and lead to major changes in the unfolding rates. We conclude that the refolding mechanism of (βα)(8)-barrel proteins is robust. It evolved early and, apparently, has remained conserved upon the diversification of sequences and functions that have taken place within this large protein family. 相似文献
48.
[reaction: see text]. (+)-Galiellalactone was synthesized starting from (R)-(+)-pulegone. Natural and synthetic galiellalactone have opposite optical rotations, demonstrating that the structure of the natural product is 1a. 相似文献
49.
Verotta L Lovaglio E Sterner O Appendino G Bombardelli E 《The Journal of organic chemistry》2004,69(23):7869-7874
Protein additives have a dramatic effect on the H(2)O(2) oxidation of hyperforin, either protecting the enolized phloroglucinol core from oxidation (human albumin) or promoting (HRP and ovalbumin) reaction pathways derived from the intermediacy of the enollactone 4, a minor component of the oxidation mixture in the absence of protein additives. To rationalize the exquisite specificity of several steps and their mechanistic oddity, an organocatalytic effect is postulated. The use of protein additives allows a straightforward and multigram preparation of the enollactone 6, an interesting multifunctionalized scaffold for bioactivity induction and/or modulation. 相似文献
50.
Sagawa H Lim J Abe K Fujii Y Higashi Y Kim SK Kurihara Y Maki A Nozaki T Omori T Sakai Y Sugimoto Y Takaiwa Y Terada S Imlay R Kirk P McNeil RR Metcalf W Myung SS Cheng CP Gu P Li J Li YK Mao ZP Xu YT Zhu YC Abashian A Gotow K Hu KP Low EH Mattson ME Piilonen L Sterner KL Lusin S Rosenfeld C Wang AT Wilson S Frautschi M Kagan H Kass R Trahern CG Kim GN Ko W Lander RL Maeshima K Malchow RL Smith JR Sparks K Stuart D Williams MC Kajino F Perticone D Poling R Thomas T Bacala A Park IH Sannes F 《Physical review letters》1989,63(21):2341-2345