Alkyl-phenyl cleavage of the lignin model compounds guaiacylglycol and glycerol-β-guaiacyl ether by Phanerochaete chrysosporium

The white rot basidiomycete Phanerochaete chrysosporium metabolized guaiacylglycol--guaiacyl ether (I) in high nitrogen, shaking and stationary cultures. 2-(o-Methoxyphenoxy) ethanol (X), 2-(o-methoxyphenoxy) acetic acid (IX) and methoxy-phydroquinone (MHQ) were identified as products of the metabolism of (I). P. chrysosporium also metabolized guaiacylglycerol--guaiacyl ether (IV) in high nitrogen stationary cultures. 2-(o-Methoxyphenoxy)-1,3 propanediol (XII) and 3-hydroxy, 2-(o-methoxy-phenyxy) propionic acid (XIV) were identified as products of the metabolism of (IV). Finally, P. chrysosporium metabolized -deoxyguaiacylglycol--guaiacyl ether (VI) and -deoxyguaiacylglycerol--guaiacyl ether (VII) in limiting nitrogen cultures. 2-(o-Methoxyphenoxy) ethanol (X) and 2-(o-methoxyphenoxy)-1,3 propanediol (XII) were identified as products of the metabolism of VI and VII respectively indicating hydroxylation of those substrates with subsequent alkyl-phenyl bond cleavage. Metabolites were identified after comparison with chemically synthesized standards by GLC-mass spectrometry.Abbreviations GLC Gas liquid chromatography - TMSi trimethylsilyl - TLC thin layer chromatography - MHQ methoxyhydroquinone     

β-Ether cleavage of the lignin model compound 4-ethoxy-3-methoxyphenylglycerol-β-guaiacyl ether and derivatives by Phanerochaete chrysosporium

The white rot basidiomycete Phanerochaete chrysosporium metabolized 4-ethoxy-3-methoxyphenyl-glycerol--guaiacyl ether (V) in low nitrogen, stationary cultures under which conditions the ligninolytic enzyme system is expressed. 4-Ethoxy-3-methoxyphenylglycerol XIII, guaicol and 4-ethoxy-3-methoxybenzyl alcohol (II) were isolated as metabolic products. Exogenously added XIII was rapidly converted to 4-ethoxy-3-methoxybenzyl alcohol indicating that it is an intermediate in the metabolism of V. P. chrysosporium also metabolized 1-(4-ethoxy-3-methoxyphenyl)-2-(2-methoxyphenoxy)-3-hydroxypropane VI. The degradation pathway for this dimer also included initial -ether cleavage and -hydroxylation of the diol product 1-(4-ethoxy-3-methoxyphenyl) 2,3 dihydroxypropane (XI) to yield the triol XIII which was cleaved at the , bond to yield 4-ethoxy-3-methoxybenzyl alcohol. Finally P. chrysosporium also cleaved the dimer 1-(4-ethoxy-3-methoxyphenyl)-2-(2-methoxyphenoxy)-1-hydroxypropane (VIII) at the -ether linkage yielding 1-(4-ethoxy-3-methoxyphenyl) 1,2 dihydroxypropane (IX) which was subsequently cleaved at the , bond to yield II. All of the results indicate that oxidative -ether cleavage is an important initial reaction in the metabolism of -aryl ether lignin substructure dimeric compounds. Metabolities were identified after comparison with chemically synthesized standards by gas liquid chromatography-mass spectrometry.Abbreviations GLC Gas liquid chromatography - TMSi trimethylsilyl - TLC thin layer chromatography     

Initial reactions in the fungal degradation of guaiacylglycerol-β-coniferyl ether,a lignin substructure model

Fusarium solani M-13-1 was shake-cultured in a medium containing guaiacylglycerol-β-coniferyl ether (I), a model compound representing the arylglycerol-β-aryl ether linkage in lignin, as sole carbon source. From the culture filtrate guaiacylglycerol-β-coniferyl aldehyde ether (II) and guaiacylglycerol-β-ferulic acid ether (III) were isolated as metabolic products. Incubation with (III) resulted in formation of guaiacylglycerol-β-vanillin ether (IV), which was further metabolized to guaiacyglycerol-β-vanillic acid ether (V). The results indicate that the cinnamyl alcohol group of (I) is initially oxidized to an aldehyde group, which is further oxidized to a carboxyl group, yielding (II) and (III). Compound (III) is converted to (IV) by the release of a C₂ fragment, and the aldehyde group of (IV) is further oxidized to a carboxyl group, giving (V). In the pathway from (I) to (V), neither oxidation of the benzylic secondary alcohol to ketone nor cleavage of the arylglycerol-β-aryl ether linkage was observed. The fungus was found to attack both erythro and threo form without distinction.     

Preparation of sulfonated poly(ether–ether–ketone) functionalized ternary graphene/AuNPs/chitosan nanocomposite for efficient glucose biosensor

A facile method of preparing water-dispersible sulfonated graphene (SPG) using sulfonated poly(ether–ether–ketone) organic polymer as a modifier was realized. A glucose biosensor was fabricated by immobilizing glucose oxidase (GO_x) on the surface of AuNPs used to modify SPG and chitosan (CH) deposited on an indium tin-oxide (ITO) glass electrode by a solution casting method. Morphological and structural characterizations confirm that the AuNPs can be efficiently applied to the SPG–CH matrix. The amperometric response of the GO_x/SPG–AuNPs–CH/ITO bioelectrode shows a broad linear range of 0.5 to 22.2 mM, with a limit of detection of 0.13 mM and a high sensitivity of 6.51 μA/(mM cm²). The excellent performance of the constructed biosensor is attributed to the large surface-to-volume ratio and electron transfer ability of SPG, the high catalytic activity of the AuNPs, and the good biocompatibility of CH. In addition, the sensor has important advantages, such as its simple preparation, fast response time (10 s), good stability (70 days), and high reproducibility. Favorable results upon examining the electrochemical response for the determination of glucose in human blood serum were obtained, without the assistance of a negligible effect of interfering bio-analytes. The results of studies show that the ternary SPG–AuNPs–CH nanocomposite may offer a new approach for developing novel types of highly sensitive and stable electrochemical biosensors.     

Species differences in biotransformation of 17α-cyanomethylestradiol 3-methyl ether

Following oral administration of 9,11- ³H-17α-cyano-methylestra-1,3,5(10)-triene-3,17-diol 3-methyl ether, urinary metabolites were studied in man, baboon, beagle dog, minipig and rat. The metabolite pattern revealed remarkable species differences, especially in quantitative respects. 17α-Cyanomethylestra-1,3,5(10)-triene-3,17-diol, 17α-cyanomethylestra-1,3,5(10)-triene-2,3,17-triol 2-methyl ether, 17α-hydroxymethylestra-1,3,5(10)-triene-3,17-diol and 17α-cyanomethylestra-1,3,5(10)-triene-3,16$\text{6}\text{5}$,17-triol were isolated as principal metabolites. In rat bile, a metabolite was tentatively identified as aγ-lactone of a 17α-carbozymethyl-16α-hydroxy compound.     

Quercetagetin 6,7,4′-trimethyl ether and 3-sulphate from Decachaeta haenkeana

Four 6-methoxylated flavonols, including a new quercetagetin derivative and its 3-potassium sulphate salt, were isolated from the aerial parts of Decachaeta haenkeana.     

Effect of ethylene glycol-bis(β-aminoethyl ether)-N,N-tetraacetic acid (EGTA) on stability and activity of methanogenic granular sludge

Summary The effect of the calcium-specific chelant ethylene glycol-bis(\-aminoethyl ether)-N,N-tetraacetic acid (EGTA) on methanogenic granular sludge from a laboratory-scale upflow anaerobic sludge-blanket (UASB) reactor fed propionate and from a full-scale reactor treating paper-mill waste-water was studied. Upon treatment with EGTA both sludge types showed a decrease in the calcium and phosphorus content and a release of protein and polysaccharides, leading to a decrease in strength of papermill granular sludge and a disintegration of propionate-grown granules. After treatment of propionate-grown granular sludge with high EGTA concentrations, the methanogenic activity with propionate and acetate as test substrates decreased by 88 and 33%, respectively. The marked reduction in propionate oxidation activity may be caused by a disruption of the special juxtapositioning of bacteria in the granules. Offsprint requests to: A. J. B. Zehnder     

Inhibition of human ether à go-go potassium channels by Ca(2+)/calmodulin

Intracellular Ca(2+) inhibits voltage-gated potassium channels of the ether à go-go (EAG) family. To identify the underlying molecular mechanism, we expressed the human version hEAG1 in XENOPUS: oocytes. The channels lost Ca(2+) sensitivity when measured in cell-free membrane patches. However, Ca(2+) sensitivity could be restored by application of recombinant calmodulin (CaM). In the presence of CaM, half inhibition of hEAG1 channels was obtained in 100 nM Ca(2+). Overlay assays using labelled CaM and glutathione S-transferase (GST) fusion fragments of hEAG1 demonstrated direct binding of CaM to a C-terminal domain (hEAG1 amino acids 673-770). Point mutations within this section revealed a novel CaM-binding domain putatively forming an amphipathic helix with both sides being important for binding. The binding of CaM to hEAG1 is, in contrast to Ca(2+)-activated potassium channels, Ca(2+) dependent, with an apparent K(D) of 480 nM. Co-expression experiments of wild-type and mutant channels revealed that the binding of one CaM molecule per channel complex is sufficient for channel inhibition.     

Biodegradation of a high molecular weight aliphatic ether – indications of an unusual biodegradation pathway

An aliphatic ether (1-phytanyl-1-octadecanyl-ether) of high molecular weight was used as a sole carbon source in degradation experiments with different aerobic bacteria. The enriched culture B5, obtained from fuel contaminated soils, was able to degrade the substance for more than 90%. A culture of Rhodococcus ruber was similarly effective. Detailed investigation of the metabolites allowed us to characterize an unusual degradation pathway via a mid-chain oxidation mechanism (`internal oxidative pathway'). Obviously, formation of intermediate alkenes mainly at the unbranched side chain was a prerequisite for bacterial degradation of the added substrate. Degradation proceeded – in spite of the usually preferred terminal oxidation – via oxidation of the internal double bond and was followed by an ester cleavage. In turn, a series of alcohols was formed which were subsequently oxidized to the respective carboxylic acids and were further metabolized via the normal -oxidation pathway.     

β-arrestin与β-肾上腺素受体

2012年度诺贝尔化学奖授予了美国科学家罗伯特.莱夫科维茨（Robert J.Lefkowitz）和布莱恩.克比尔卡（Brian K.Kobilka）,以表彰他们在G蛋白偶联受体研究中的贡献。从Robert J.Lefkowitz最初研究β-肾上腺素受体（β-adrenergic receptor,β-AR）减敏机制时发现β-arrestin1至今已有20多年,随着对β-arrestin在细胞信号转导中作用研究的逐渐深入,发现β-arrestin参与β-AR的减敏、内化和降解;近年来又发现,依赖β-arrestin的β-AR信号转导通路具有＂偏向激活＂现象,并提示这种依赖β-arrestin的＂偏向激活＂信号转导通路具有心脏保护作用。β-肾上腺素受体阻滞剂的发现和临床应用被视为20世纪药物治疗学上里程碑式的进展,是药物防治心脏疾病的最伟大突破,很多心血管药物都以β-AR为靶点。但是,由于目前受体药物均是针对受体本身的调控,这样在阻断了受体介导的病理性信号通路和功能的同时,也阻断了受体介导的正常生理性信号通路和功能,造成了严重的毒副作用。所以,研发能选择性阻滞β-AR过度激活介导的病理性信号通路和功能的同时,保留受体介导的正常生理性信号通路和功能（如β-arrestin信号通路）的药物,对治疗心血管疾病有重要意义,受体功能选择性的配体药物将成为未来药物的研究方向。该文将回顾β-arrestin的发现过程,综述其与β-AR的相互作用,期望能为心脏疾病的药物治疗提供参考。     

Synthesis and biological activity of ester and ether analogues of α-galactosylceramide (KRN7000)

α-Galactosylceramide (αGalCer, KRN7000) has been identified as a modulator of immunological processes through its capacity to bind iNKT cells mediated by CD1d molecules. Some analogues in while the amide group in αGalCer is replaced with ester or ether groups were synthesized from d-arabinitol or l-ribose to evaluate their ability to activate iNKT cells. Ester analogues 30a, 31a, and 61 showed activity for IFNγ and IL-4 production of iNKT cells, while ether (31b) and 4-methoxy ester (76) analogues of α-galactosylceramide were not active for iNKT cells.     

Synthesis of new steroid haptens for radioimmunoassay. Part IV. 3-O-carboxymethyl ether derivatives of estrogens. Specific antisera for radioimmunoassay of estrone,estradiol-17β, and estriol

The syntheses of 3-O-carboxymethyl ether derivatives of estrone, estradiol-17β, and estriol and the preparation of their bovine serum albumin (BSA) conjugates are described. These conjugates were employed for the generation of specific antisera suitable for radioimmunoassay (RIA) of estrone, estradiol-17β, and estriol. The previous concept that specific antisera for estrogens cannot be obtained by employing estrogens derivatized at the 3-position is unfounded.     

A reevaluation of an agent proposed for imaging oestrogen receptors: 17α-[125I]-iodovinyl-11β-methoxyoestradiol-3-methyl ether ([125I]VMEME)

The metabolism of an iodinated steroid, 17α-[¹²⁵I]iodovinyl-11β-methoxyoestradiol-3-methyl ether ([¹²⁵I]VMEME), previously proposed as a potential agent for imaging oestrogen receptor-containing tissues, has been studied and the conditions for synthesis and labelling redefined. It is confirmed that, although the compound does not itself have significant receptor-binding affinity, a metabolite is active. Because of its high solubility in fat and the consequential low contrast of small receptor-containing tumours, there is little prospect of successful early imaging of small axillary or internal mammary lymph node metastases from human breast cancer with this compound. Some more general implications of this finding are considered.     

Enhanced DNA binding of 9-ω-amino alkyl ether analogs from the plant alkaloid berberine

To understand the structure-activity relationship of isoquinoline alkaloids, absorption, fluorescence, circular dichroism, and thermodynamics were employed to study the interaction of five C-9-ω-amino alkyl ether analogs from the plant alkaloid berberine with double-stranded calf thymus DNA. The C-9 derivatization resulted in dramatic enhancements in the fluorescence emission of these compounds. The most remarkable changes in the spectral and binding properties were in the BC4 and BC5 derivatives. Interactions of these analogs, which have an additional recognition motif with DNA, were evaluated through different spectroscopic and calorimetric titration experiments. The analogs remarkably enhanced the DNA binding affinity and the same was directly dependent on the alkyl chain length. The analog with six alkyl chains enhanced the DNA binding affinity by about 33 times compared with berberine. The binding became more entropically driven with increasing chain length. These results may be of potential use in the design of berberine derivatives and understanding of the structure-activity relationship for improved therapeutic applications.     

Sinopestalotiollides A–D,cytotoxic diphenyl ether derivatives from plant endophytic fungus Pestalotiopsis palmarum

Four new diphenyl ether derivatives, sinopestalotiollides A–D (1–4), one new natural α-pyrone product (11), as well as twelve known compounds (5–1?7), were obtained from the ethyl acetate extract of the endophytic fungus Pestalotiopsis palmarum isolated from the leaves of medicinal plant Sinomenium acutum (Thunb.) Rehd et Wils. The structures were elucidated by HR-ESI-MS and NMR spectrometry data. Bioassay experiments revealed that compounds 1–4 and 11 exhibited strong to weak cytotoxicities against three human tumor cell lines Hela, HCT116 and A549.     

Functional expression of the voltage-gated neuronal mammalian potassium channel rat ether à go-go1 in yeast.

It has been shown previously that heterologous expression of inwardly rectifying potassium channels (K+-channels) from plants and mammals in K+-transport defective yeast mutants can restore the ability of growth in media with low [K+]. In this study, the functional expression of an outward rectifying mammalian K+-channel in yeast is presented for the first time. The outward-rectifying mammalian neuronal K+-channel rat ether à go-go channel 1 (rEAG1, Kv 10.1) was expressed in yeast (Saccharomyces cerevisiae) strains lacking the endogenous K+-uptake systems and/or alkali-metal-cation efflux systems. It was found that a truncated channel version, lacking almost the complete intracellular N-terminus (rEAG1 Delta 190) but not the full-length rEAG1, partially complemented the growth defect of K+-uptake mutant cells (trk1,2 Delta tok1 Delta) in media containing low K+ concentrations. The expression of rEAG1 Delta 190 in a strain lacking the cation efflux systems (nha1 Delta ena1-4 Delta) increased the sensitivity to high monovalent cation concentrations. Both phenotypes were observed, when rEAG1 Delta 190 was expressed in a trk1,2 Delta and nha1, ena1-4 Delta mutant strain. In the presence of K+-channel blockers (Cs+, Ba2+ and quinidine), the growth advantage of rEAG1 Delta 190 expressing trk1,2 tok1 Delta cells disappeared, indicating its dependence on functional rEAG1 channels. The results demonstrate that S. cerevisiae is a suitable expression system even for voltage-gated outward-rectifying mammalian K+-channels.