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DavidA. Carcache SimoneR. Hrtner Andreas Bertogg Franois Diederich Arnulf Dorn HansPeter Mrki Christoph Binkert Daniel Bur 《Helvetica chimica acta》2003,86(6):2192-2209
A new class of nonpeptidic inhibitors of the malarial aspartic protease plasmepsin II (PMII) with up to single‐digit micromolar activities (IC50 values) was developed by structure‐based de novo design. The active‐site matrix used in the design was based on an X‐ray crystal structure of PMII, onto which the major conformational changes seen in the structure of renin upon complexation of 4‐arylpiperidines – including the unlocking of a new hydrophobic (flap) pocket – were modeled. The sequence identity of 35% between mature renin and PMII had prompted us to hypothesize that an induced‐fit adaptation around the active site as observed in renin might also be effective in PMII. The new inhibitors contain a central 11‐azatricyclo[6.2.1.02,7]undeca‐2(7),3,5‐triene core, which, in protonated form, undergoes ionic H‐bonding with the two catalytic Asp residues at the active site of PMII (Figs. 1 and 2). This tricyclic scaffold is readily prepared by a Diels? Alder reaction between an activated pyrrole and a benzyne species generated in situ (Scheme 1). Two substituents with naphthyl or 1,3‐benzothiazole moieties are attached to the central core (Schemes 1–4) for accommodation in the hydrophobic flap and S1/S3 (or S2′, depending on the optical antipode of the inhibitor) pockets at the active site of the enzyme. The most‐potent inhibitors (±)‐ 19a – 19c (IC50 3–5 μM ) and (±)‐ 23b (2 μM ) (Table) bear an additional Cl‐atom on the 1,3‐benzothiazole moiety to fully fill the rear of the flap pocket. Optimization of the linker between the tricyclic scaffold and the 1,3‐benzothiazole moiety, based on detailed conformational analysis (Figs. 3 and 4), led to a further small increase in inhibitory strength. The new compounds were also tested against other aspartic proteases. They were found to be quite selective against renin, while the selectivity against cathepsin D and E, two other human aspartic proteases, is rather poor (Table). The detailed SARs established in this investigation provide a valuable basis for the design of the next generations of more‐potent and ‐selective PMII inhibitors with potential application in a new antimalarial therapy. 相似文献
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Numerical Algorithms - In this article we establish exponential moment bounds, moment bounds in fractional order smoothness spaces, a uniform Hölder continuity in time, and strong convergence... 相似文献
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Novel Hyperbranched Poly([1,2,3]‐triazole)s Derived from AB2 Monomers by a 1,3‐Dipolar Cycloaddition
Arnulf J. Scheel Hartmut Komber Brigitte I. Voit 《Macromolecular rapid communications》2004,25(12):1175-1180
Summary: Novel hyperbranched poly([1,2,3]‐triazole)s were synthesized from several AB2 monomers by a 1,3‐dipolar cycloaddition reaction. The compound 3,5‐bis(propargyloxy)benzyl azide was polymerized thermally at room temperature leading to 1,4‐ and 1,5‐disubstituted poly([1,2,3]‐triazole) and catalytically leading only to the 1,4‐disubstituted poly([1,2,3]‐triazole). Only the thermal reaction led to fully soluble products. The AB2 monomers containing an internal alkyne A unit could be autopolymerized thermally under mild reaction conditions leading to soluble, high‐molecular‐weight hyperbranched poly([1,2,3] triazole)s. All products were characterized by detailed NMR investigations.
18.
Hyperbranched polycarbonates were synthesized successfully via the A2 + B3 route by the reaction of a bis(carbonylimidazolide) with triethanolamine. These polymers containing the carbonate group as thermolabile moiety are decomposing into volatile products at around 200°C. The polymers were characterized with 1H/13C NMR spectroscopy, SEC, DSC and TGA techniques. 相似文献
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Aiguo Shen Benjian Zhang Jie Ping Wei Xie Patrice Donfack Seong‐Joon Baek Xiaodong Zhou Hui Wang Arnulf Materny Jiming Hu 《Journal of Raman spectroscopy : JRS》2009,40(5):550-555
Micro‐Raman spectroscopy (MRS) was utilized for the first time to evaluate the effect of indole‐3‐carbinol (I3C) on acute alcoholic liver injury in vivo. In situ Raman analysis of tissue sections provided distinct spectra that can be used to distinguish alcoholic liver injury as well as ethanol‐induced liver fibrosis from the normal state. Sixteen mice with liver diseases including acute liver injury and chronic liver fibrosis, and eight mice with normal liver tissues, and eight remedial mice were studied employing the Raman spectroscopic technique in conjunction with biomedical assays. The biochemical changes in mouse liver tissue when liver injury/fibrosis occurs such as the loss of reduced glutathione (GSH), and the increase of collagen (α‐helix protein) were observed by MRS. The intensity ratio of two Raman peaks (I1450/I666) and in combination with statistical analysis of the entire Raman spectrum was found capable of classifying liver tissues with different pathological features. Raman spectroscopy therefore is an important candidate for a nondestructive in vivo screening of the effect of drug treatment on liver disease, which potentially decreases the time‐consuming clinical trials. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
20.
Animesh K. Ojha Patrice Donfack Arnulf Materny 《Journal of Raman spectroscopy : JRS》2012,43(9):1183-1190
Complex concentration‐dependence of surface‐enhanced Raman scattering (SERS) and UV–Vis absorption of Ag‐nanoparticles (AgNPs) mixed with Gly has been observed. Surprisingly, with decreasing Gly concentration, a new band in UV–Vis absorption of AgNPs/Gly mixtures is found to red‐shift with increasing intensity, until a turning point at a critical concentration. Further diluting Gly, the new band blue‐shifts with decreasing intensity. Similarly, the SERS intensities of Gly bands at 615 and 905 cm–1 consistently increase with decreasing Gly concentrations, reaching maxima at the critical concentration. This agrees consistently with the variation in position and intensity of the new developing plasmon absorption band. Interestingly, transmission electron microscopy (TEM) revealed Gly‐induced modifications of AgNPs, including a reassembling and increasing aspect ratio with deceasing Gly concentration. The concentration‐dependent behavior of UV–Vis absorption, SERS, and TEM of AgNPs/Gly mixtures could be due to the complex nature of Gly‐AgNPs interaction depending on the molecular density, as supported by TEM images. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献