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1.
Igor Loncaric Gabrielle L. Stalder Kemal Mehinagic Renate Rosengarten Franz Hoelzl Felix Knauer Chris Walzer 《PloS one》2013,8(12)
In order to test whether rooks (Corvus frugilegus) represent good indicators for the potential circulation of antibiotics in their native habitat, two populations with different migratory behavior were tested for the presence of beta-lactamase producing Enterobacteriaceae and methicillin-resistant Staphylococcus aureus (MRSA). In all, 54 and 102 samples of fresh feces of a migratory and a resident population were investigated. A total of 24 and 3 cefotaxime-resistant enterobacterial isolates were obtained from the migratory and resident population, respectively. In these isolates CTX-M-1 (n = 15), CTX-M-3 (n = 3), and CTX-M-15 (n = 3) genes were detected. TEM-1 and OXA-1 were associated with CTX-M in 3 and 2 isolates, respectively. In two E. coli isolates CMY-2 could be detected, where from one isolate displayed an overexpression of chromosomal AmpC as well. Among E. coli isolates the most common phylogenetic group was A (n = 11) and ST1683 (n = 5). In one E. coli of B2-ST131 the rfbO25b locus was detected. Three Enterobacter isolates were stably derepressed AmpC-producers. In five samples of the migratory population, PVL positive MRSA could be isolated. Two isolates were typed SCCmec IVa, spa type t127, and ST1. Three isolates carried a SCCmec type IVc, with spa type t852 and ST22. The highly significant difference of the occurrence of antibiotic resistance between the migratory population from eastern Europe compared to resident population in our study indicates that rooks may be good indicator species for the evaluation of environmental contamination with antibiotic resistant bacteria, especially due to their ecology, foraging behavior and differing migratory behavior. 相似文献
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Nimra Khan Dylan Pelletier Thomas S. McAlear Nathalie Croteau Simon Veyron Andrew N. Bayne Corbin Black Muneyoshi Ichikawa Ahmad Abdelzaher Zaki Khalifa Sami Chaaban Igor Kurinov Gary Brouhard Susanne Bechstedt Khanh Huy Bui Jean-François Trempe 《Structure (London, England : 1993)》2021,29(6):572-586.e6
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Membrane insertion and lateral diffusion of fluorescence-labelled cytochrome c oxidase subunit IV signal peptide in charged and uncharged phospholipid bilayers. 总被引:5,自引:0,他引:5
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The synthetic 25-residue signal peptide of cytochrome c oxidase subunit IV was labelled with the fluorophor 7-nitrobenz-2-oxa-1,3-diazole (NBD) at its single cysteine residue. Addition of small unilamellar vesicles of 1-palmitoyl 2-oleoyl phosphatidylcholine (POPC) to the labelled peptide resulted in a shift of the NBD excitation and emission spectra to shorter wavelengths. Binding of the peptide to the vesicles was measured by the increase in the fluorescence emission yield. A surface partition constant of (3.9 +/- 0.5) x 10(3) M-1 was derived from these titrations. When the membrane contained, in addition to POPC, negatively charged 1-palmitoyl 2-oleoyl phosphatidylglycerol (POPG), the NBD fluorescence spectra were further shifted to shorter wavelengths and exhibited increased quantum yields. The apparent partition constants were increased to 10(4)-10(5) M-1 for vesicles with 20 or 100 mol% POPG. Lateral diffusion of the peptide was measured by fluorescence recovery after photobleaching in multibilayers of POPC, POPG, POPC/POPG (4:1) and 1,2-dimyristoyl phosphatidylcholine. The lateral diffusion coefficients of the peptide in bilayers of POPC (8 x 10(-8) cm2/s at 21 degrees C) were 1.5-1.6-fold greater than those of NBD-labelled phospholipids (5 x 10(-8) cm2/s at 21 degrees C), but 1.5-1.8-fold smaller (3 x 10(-8) cm2/s in 20% POPG and at 21 degrees C) than the lipid diffusion coefficients in the negatively charged bilayers. It is concluded that the signal peptide associates with phospholipid bilayers in two different forms, which depend on the lipid charge. The experiments with POPC bilayers are well explained by a model in which the peptide partitions into the region of the phospholipid head-groups and diffuses along the membrane/water interface. If POPG is present in the membrane, electrostatic attractions between the basic residues of the peptide and the acidic lipid head-groups result in a deeper penetration of the bilayer. For this case, two models that are both consistent with the experimental data are discussed, in which the peptide either forms an oligomer of three to six partially helical membrane-spanning monomers, or inserts into the bilayer with its amphiphilic helical segment aligned parallel to the plane of the membrane and located near the head-group and outer hydrocarbon region of the bilayer. 相似文献
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The soybean trypsin inhibitor conjugate with a thermo-reactive water soluble polymer, poly(N-vinyl caprolactam), was successfully
used for thermally induced affinity precipitation of trypsin. The validity of the developed procedure was proven by a model
separation of trypsin from dilute solution containing a large excess of bovine serum albumin. 相似文献
9.
Igor A. Krasheninnikov Anton A. Komar Ivan A. Adzhubei 《Journal of Protein Chemistry》1991,10(5):445-453
Examination of nascent globin peptides accumulatingin vitro during globin synthesis in rabbit reticulocyte lysates was carried out. A view was supported that nonrandom distribution of codons with different usage frequencies in mRNA may determine the messenger's translation kinetics. Regions of reduced translation of - and -globin polypeptide chains were localized, and the cotranslational protein-folding model suggested previously was substantiated. An active conjunction of synthesis and folding of proteins was proposed as one of the main destinations of a translation nonuniformity. 相似文献
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Phospholipid bilayers have been formed on glass, quartz, and silicon surfaces by a sequential transfer of two monolayers at a pressure of approximately 40 dyn/cm from the air-water interface to the solid substrates. Lateral diffusion measurements of L-alpha-dipalmitoylphosphatidylcholine (DPPC) bilayers supported on oxidized silicon wafers reveal two sharp phase transitions at temperatures similar to those found in multilayer systems with several different techniques. The diffusion measurements obtained using fluorescence recovery after pattern photobleaching provide evidence for the existence of an intermediate (probably P beta' or ripple) phase in single bilayers. While in the intermediate and high temperature (liquid-crystalline L alpha) phase, the diffusion coefficients do not vary very much with temperature, a strong temperature dependence is observed in the low temperature (gel L beta') phase. This is attributed to defect-mediated diffusion. Lipids in silicon supported bilayers made from L-alpha-dioleoylphosphatidylcholine (DOPC) or L-alpha-dimyristoylphosphatidylcholine (DMPC) diffuse rapidly above their respective chain-melting transition temperatures. Arrhenius plots show straight lines with activation energies of 40.9 and 43.7 kJ/mol, respectively. Supported DPPC bilayers on oxidized silicon form long tubular liposomes when heated through their oxidized silicon form long tubular liposomes when heated through their chain-melting-phase transition, as viewed with epifluorescence microscopy. It is suggested that this is a consequence of the expansion of the lipid on the fixed solid support. Conversely, DOPC bilayers form large void areas on this substrate upon cooling. Large circular membrane defects (holes) are observed under rapid coating conditions.(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献