Here we introduce silyl ether linkage as a novel dynamic covalent motif for dynamic material design. Through introduction of a neighboring amino moiety, we show that the silyl ether exchange rate can be accelerated by almost three orders of magnitude. By incorporating such silyl ether linkages into covalently cross-linked polymer networks, we demonstrate dynamic covalent network polymers displaying both malleability and reprocessability. The malleability of the networks is studied by monitoring stress relaxation at varying temperature, and their topology freezing temperatures are determined. The tunable dynamic properties coupled with the high thermal stability and reprocessability of silyl ether-based networks open doors to many potential applications for this family of materials.

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The abuse of antibacterial drugs imposes a selection pressure on bacteria that has driven the evolution of multidrug resistance in many pathogens. Our efforts to discover novel classes of antibiotics to combat these pathogens resulted in the discovery of amycolamicin (AMM). The absolute structure of AMM was determined by NMR spectroscopy, X-ray analysis, chemical degradation, and modification of its functional groups. AMM consists of trans-decalin, tetramic acid, two unusual sugars (amycolose and amykitanose), and dichloropyrrole carboxylic acid. The pyranose ring named as amykitanose undergoes anomerization in methanol. AMM is a potent and broad-spectrum antibiotic against Gram-positive pathogenic bacteria by inhibiting DNA gyrase and bacterial topoisomerase IV. The target of AMM has been proved to be the DNA gyrase B subunit and its binding mode to DNA gyrase is different from those of novobiocin and coumermycin, the known DNA gyrase inhibitors.

The WalK (a histidine kinase)/WalR (a response regulator, aka YycG/YycF) two-component system is indispensable in the signal transduction pathway for the cell-wall metabolism of Bacillus subtilis and Staphylococcus aureus. The inhibitors directed against WalK would be expected to have a bactericidal effect. After we screened 1368 culture broths of Streptomyces sp. by a differential growth assay, walkmycin A, B and C, which were produced by strain MK632-100F11, were purified using silica-gel column chromatography and HPLC. In this paper, the chemical structure of the major product (walkmycin B) was determined to be di-anthracenone (C 44 H 44 Cl 2 O 14 ), which was very similar to BE40665A. MICs of walkmycin B against B. subtilis and S. aureus were 0.39 and 0.20 lg ml À1 , and IC 50 measurements against WalK were 1.6 and 5.7 lM, respectively. To clarify the affinity between WalK and walkmycin B, surface plasmon resonance was measured to obtain the equilibrium dissociation constant, K D1 , of 7.63 lM at the higher affinity site of B. subtilis WalK. These results suggest that walkmycin B inhibits WalK autophosphorylation by binding to the WalK cytoplasmic domain.

Einbahnstraße: Eine neue Familie von λ5‐Phospha[7]helicenen, die eindimensionale säulenartige Stapel im festen Zustand bilden, wurde synthetisiert (siehe Schema). Benachbarte Stapel haben entgegengesetzte Dipolrichtungen. Im Fall des Helicens auf Basis von racemischem Phospholsulfid bestehen Säulen mit einer der beiden Dipolrichtungen aus dem einen Enantiomer, Säulen mit entgegengesetzter Dipolrichtung aus dem anderen.

ABSTRACT:Glucuronidation of morphine in humans is predominantly catalyzed by UDP-glucuronosyltransferase 2B7 (UGT2B7). Since our recent research suggested that cytochrome P450s (P450s) interact with UGT2B7 to affect its function [Takeda S et al. (2005) Mol Pharmacol 67:665-672], P450 inhibitors are expected to modulate UGT2B7-catalyzed activity. To address this issue, we investigated the effects of P450 inhibitors (cimetidine, sulfaphenazole, erythromycin, nifedipine, and ketoconazole) on the UGT2B7-catalyzed formation of morphine-3-glucuronide (M-3-G) and morphine-6-glucuronide (M-6-G). Among the inhibitors tested, ketoconazole was the most potent inhibitor of both M-3-G and M-6-G formation by human liver microsomes. The others were less effective except that nifedipine exhibited an inhibitory effect on M-6-G formation comparable to that by ketoconazole. Neither addition of NADPH nor solubilization of liver microsomes affected the ability of ketoconazole to inhibit morphine glucuronidation. In addition, ketoconazole had an ability to inhibit morphine UGT activity of recombinant UGT2B7 freed from P450. Kinetic analysis suggested that the ketoconazole-produced inhibition of morphine glucuronidation involves a mixedtype mechanism. Codeine potentiated inhibition of morphine glucuronidation by ketoconazole. In contrast, addition of another substrate, testosterone, showed no or a minor effect on ketoconazole-produced inhibition of morphine UGT. These results suggest that 1) metabolism of ketoconazole by P450 is not required for inhibition of UGT2B7-catalyzed morphine glucuronidation; and 2) this drug exerts its inhibitory effect on morphine UGT by novel mechanisms involving competitive and noncompetitive inhibition.

WalK, a histidine kinase, and WalR, a response regulator, make up a two-component signal transduction system that is indispensable for the cell-wall metabolism of low GC Gram-positive bacteria. WalK inhibitors are likely to show bactericidal effects against methicillin-resistant Staphylococcus aureus . We discovered a new WalK inhibitor, designated waldiomycin, by screening metabolites from actinomycetes. Waldiomycin belongs to the family of angucycline antibiotics and is structurally related to dioxamycin. Waldiomycin inhibits WalK from S. aureus and Bacillus subtilis at IC50s 8.8 and 10.2 μM, respectively, and shows antibacterial activity with MICs ranging from 4 to 8 μg ml(-1) against methicillin-resistant S. aureus and B. subtilis.

2,3,7, and related substances are a class of environmental pollutants with suspected toxic effects on reproductive and developmental processes. This study investigated a hypothesis that maternal exposure to TCDD damages gonadotropin-regulated steroidogenesis in fetal gonads to imprint defects in sexual behavior as well as the maturation of gonadal tissues. Oral administration of 1 g/kg TCDD to pregnant Wistar rats at gestational day (GD) 15 attenuated the expression of luteinizing hormone (LH), a regulator of gonadal steroidogenesis, in the pituitaries of male and female fetuses at GD20. TCDD treatment also reduced the fetal expression of testicular and ovarian steroidogenic proteins, including steroidogenic acute-regulatory protein. These changes in pituitary and gonadal proteins were fetus-specific, and this seems not to be because of the greater delivery of TCDD to the brain of fetuses than adults. This is because a reduction in LH production was not reproduced even although TCDD was administered intraventricularly to adult rats. Direct supplementation of equine chorionic gonadotropin (eCG), an LH-mimicking hormone, to TCDD-exposed fetuses at GD17 restored the reduced expression of gonadal steroidogenic proteins. Maternal exposure to TCDD delayed the development of gonadal tissues in male and female pups and impaired their sexual behavior. However, eCG treatment at the fetal stage again restored not only tissue maturation but also many of the behavioral defects that occurred at adulthood. These results demonstrate that TCDD disrupts steroidogenesis in fetuses by targeting pituitary gonadotropin production and imprints demasculinization in males and defeminization in females in terms of their copulatory behavior.