Shift to Pseudomonic acid B production in P. fluorescens NCIMB10586 by mutation of mupirocin tailoring genes mupO, mupU, mupV, and macpE

Mupirocin, a polyketide-derived antibiotic from Pseudomonas fluorescens NCIMB10586, is a mixture of pseudomonic acids (PA) that target isoleucyl-tRNA synthase. The mup gene cluster encodes both type I polyketide synthases and monofunctional enzymes that should play a role during the conversion of the product of the polyketide synthase into the active antibiotic (tailoring). By in-frame deletion analysis of selected tailoring open-reading frames we show that mupQ, mupS, mupT, and mupW are essential for mupirocin production, whereas mupO, mupU, mupV, and macpE are essential for production of PA-A but not PA-B. Therefore, PA-B is not simply produced by hydroxylation of PA-A but is either a precursor of PA-A or a shunt product. In the mupW mutant, a new metabolite lacking the tetrahydropyran ring is produced, implicating mupW in oxidation of the 16-methyl group.     

Transport and Magnetic Resonance Studies of Polyaniline

Conductivity, thermoelectric power, spin concentration and spin dynamics has been measured in polyaniline samples equilibrated at different pH. Data provide evidence for Metal-Insulator transition upon pH variation.     

Methods for Studying Endocytotic Pathways of Herpesvirus Encoded G Protein-Coupled Receptors

Endocytosis is a fundamental process involved in trafficking of various extracellular and transmembrane molecules from the cell surface to its interior. This enables cells to communicate and respond to external environments, maintain cellular homeostasis, and transduce signals. G protein-coupled receptors (GPCRs) constitute a family of receptors with seven transmembrane alpha-helical domains (7TM receptors) expressed at the cell surface, where they regulate physiological and pathological cellular processes. Several herpesviruses encode receptors (vGPCRs) which benefits the virus by avoiding host immune surveillance, supporting viral dissemination, and thereby establishing widespread and lifelong infection, processes where receptor signaling and/or endocytosis seem central. vGPCRs are rising as potential drug targets as exemplified by the cytomegalovirus-encoded receptor US28, where its constitutive internalization has been exploited for selective drug delivery in virus infected cells. Therefore, studying GPCR trafficking is of great importance. This review provides an overview of the current knowledge of endocytic and cell localization properties of vGPCRs and methodological approaches used for studying receptor internalization. Using such novel approaches, we show constitutive internalization of the BILF1 receptor from human and porcine γ-1 herpesviruses and present motifs from the eukaryotic linear motif (ELM) resources with importance for vGPCR endocytosis.     

1H‐Pyrrole‐2‐carbothioamide

The reaction of ethoxy­carbonyl­pyrrole‐2‐thio­carbox­amide with sodium hydro­xide affords the known title compound, C₅H₆N₂S, whose structure shows a three‐dimensional hydrogen‐bonded lattice.     

Polarizability anisotropies of cyano-substituted azulene,biphenyl, 2,2'- bipyridyl and naphthalene

The conformations of a number of cyano-substituted aromatic model mesogens with actual or potential application in liquid crystals have been obtained using density functional B-LYP/6-311G(d) methodology. Dipole polarizability tensors have been computed at Hartree-Fock and B3-LYP levels of theory using Spackman's recommended basis sets, in order to obtain polarizability anisotropies, and to compare them with those of the parent compounds. The results indicate that 6-cyanoazulene is a potentially important mesogenic component, having a polarizability anisotropy not much less than 4-cyano-2,2'-bipyridyl. Electric dipole transition moments and oscillator strengths to the lowest singlet and triplet excited states have also been estimated for the cyanoazulenes, using a Configuration-Interaction Singles CIS/6-311G(d) approximation.     

Correlation between the “fishtail” effect in the magnetization and the Schottky contribution in the specific heat of high purity YBA2Cu3O7−δ crystals

The irreversibility of the magnetization and the low temperature specific heat of high purity YBa₂Cu₃O_7– crystals are investigated. We find that the heat treatment that suppresses the magnetic fishtail effect also suppresses the Schottky component of the heat capacity. Both effects originate from the distribution of oxygen states.     

Characterization of the mupirocin biosynthesis gene cluster from Pseudomonas fluorescens NCIMB 10586

The polyketide antibiotic mupirocin (pseudomonic acid) produced by Pseudomonas fluorescens NCIMB 10586 competitively inhibits bacterial isoleucyl-tRNA synthase and is useful in controlling Staphylococcus aureus, particularly methicillin-resistant Staphylococcus aureus. The 74 kb mupirocin biosynthesis cluster has been sequenced, and putative enzymatic functions of many of the open reading frames (ORFs) have been identified. The mupirocin cluster is a combination of six larger ORFs (mmpA-F), containing several domains resembling the multifunctional proteins of polyketide synthase and fatty acid synthase type I systems, and individual genes (mupA-X and macpA-E), some of which show similarity to type II systems (mupB, mupD, mupG, and mupS). Gene knockout experiments demonstrated the importance of regions in mupirocin production, and complementation of the disrupted gene confirmed that the phenotypes were not due to polar effects. A model for mupirocin biosynthesis is presented based on the sequence and biochemical evidence.     

Determination of estrogens in river water by gas chromatography-negative-ion chemical-ionization mass spectrometry.

A method for the determination of estrogens (17alpha-estradiol, 17beta-estradiol, estrone, ethynyl estradiol, and estriol) as pentafluorobenzyl-trimethylsilyl (PFB-TMS) derivatives by gas chromatography-mass spectrometry (GC-MS) with negative-ion chemical-ionization (NICI) is described. The NICI of all the derivatives produced an intense [M-PFB]- ion as the base peak. The reagent gas (methane) flow-rate and the ion source temperature were determined to be 2.0 ml/min and 240 degrees C, respectively, for the optimized NICI-selected ion monitoring (SIM) conditions. The sensitivities of the PFB-TMS derivatives in the NICI mode were 8.0-130 times higher than those of the PFB-TMS derivatives in electron ionization (EI) mode, and 12-25 times higher than those of all the TMS derivatives in the EI mode. This method was applied to the analysis of estrogens in river water using a solid-phase extraction as the sample preparation. The recoveries of the target chemicals from a river-water sample spiked with standards at 2 ng/l level were 85.8-126.5% (RSD, 6.2-13.0%). The methodical detection limits ranged from 0.10 to 0.28 ng/l.     

Synthesis of Bio-Inspired 1,3-Diarylpropene Derivatives via Heck Cross-Coupling and Cytotoxic Evaluation on Breast Cancer Cells

The Heck cross-coupling reaction is a well-established chemical tool for the synthesis of unsaturated compounds by formation of a new C-C bond. In this study, 1,3-diarylpropene derivatives, designed as structural analogues of stilbenoids and dihydrostilbenoids, were synthesised by the palladium-catalysed reactions of 2-amidoiodobenzene derivatives with either estragole or eugenol. The products were obtained with high (E) stereoselectivity but as two regioisomers. The ratios of isomers were found to be dependent on the nature of the allylbenzene partner and were rationalised by electronic effects exercising a determining influence in the β-hydride elimination step. In addition, the cytotoxic effects of all the Heck reaction products were evaluated against MCF-7 and MDA-MB-231 human breast cancer cells, with unpromising results. Among all, compound 7d exhibited weak cytotoxic activity towards MCF-7 cell lines with IC₅₀ values of 47.92 µM in comparison with tamoxifen and was considered to have general toxicity (SI value < 2).