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41.
S.D. HA K.G. MACIOROWSKI S.C. RICKE 《Journal of Rapid Methods and Automation in Microbiology》1997,5(1):75-85
This study was designed to evaluate the effect of ethyl alcohol as a potential treatment for reduction of Salmonella populations in poultry feed. Growth rate of S. typhimurium in tryptic soy broth was significantly reduced by addition of greater than 0.3% volume/volume of ethyl alcohol and growth was completely inhibited by addition of 5% ethyl alcohol. Ethyl alcohol concentrations of 20% volume/weight and greater significantly reduced initial S.typhimurium populations in poultry feed (for 20% treated, 2.31 ± 0.31 vs 3.39 ± 0.29 for untreated; P < 0.05). When feed treatment was administered either before or after inoculation of S. typhimurium with 60% ethyl alcohol or 0.04% buffered propionic acid, populations in feeds treated after inoculation were decreased to a nondetection level (< 1.0 log10 CFU/g) by ethyl alcohol treatment but not by other treatments. Ethyl alcohol treatment may have the potential for reducing Salmonella spp. contamination in poultry feed. 相似文献
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A covalently bound photoisomerizable agonist. Comparison with reversibly bound agonists at electrophorus electroplaques 下载免费PDF全文
HA Lester ME Krouse MM Nass NH Wassermann BF Erlanger 《The Journal of general physiology》1980,75(2):207-232
After disulphide bonds are reduced with dithiothreitol, trans-3- (α-bromomethyl)-3’-[α- (trimethylammonium)methyl]azobenzene (trans-QBr) alkylates a sulfhydryl group on receptors. The membrane conductance induced by this “tethered agonist” shares many properties with that induced by reversible agonists. Equilibrium conductance increases as the membrane potential is made more negative; the voltage sensitivity resembles that seen with 50 [mu]M carbachol. Voltage- jump relaxations follow an exponential time-course; the rate constants are about twice as large as those seen with 50 μM carbachol and have the same voltage and temperature sensitivity. With reversible agonists, the rate of channel opening increases with the frequency of agonist-receptor collisions: with tethered trans-Qbr, this rate depends only on intramolecular events. In comparison to the conductance induced by reversible agonists, the QBr-induced conductance is at least 10-fold less sensitive to competitive blockade by tubocurarine and roughly as sensitive to “open-channel blockade” bu QX-222. Light-flash experiments with tethered QBr resemble those with the reversible photoisomerizable agonist, 3,3’,bis-[α-(trimethylammonium)methyl]azobenzene (Bis-Q): the conductance is increased by cis {arrow} trans photoisomerizations and decreased by trans {arrow} cis photoisomerizations. As with Bis-Q, ligh-flash relaxations have the same rate constant as voltage-jump relaxations. Receptors with tethered trans isomer. By comparing the agonist-induced conductance with the cis/tans ratio, we conclude that each channel’s activation is determined by the configuration of a single tethered QBr molecule. The QBr-induced conductance shows slow decreases (time constant, several hundred milliseconds), which can be partially reversed by flashes. The similarities suggest that the same rate-limiting step governs the opening and closing of channels for both reversible and tethered agonists. Therefore, this step is probably not the initial encounter between agonist and receptor molecules. 相似文献
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Adenylyltransferase is a bifunctional enzyme that controls the enzymatic activity of dodecameric glutamine synthetase in Escherichia coli by reversible adenylylation and deadenylylation. Previous studies showed that the two similar but chemically distinct reactions are carried out by separate domains within adenylyltransferase. The N-terminal domain carries the deadenylylation activity, and the C-terminal domain carries the adenylylation activity [Jaggi R, van Heeswijk WC, Westerhoff HV, Ollis DL & Vasudevan SG (1997) EMBO J16, 5562-5571]. In this study, we further map the domain junctions of adenylyltransferase on the basis of solubility and enzymatic analysis of truncation constructs, and show for the first time that adenylyltransferase has three domains: the two activity domains and a central, probably regulatory (R), domain connected by interdomain Q-linkers (N-Q1-R-Q2-C). The various constructs, which have the opposing domain and or central domain removed, all retain their activity in the absence of their respective nitrogen status indicator, i.e. PII or PII-UMP. A panel of mAbs to adenylyltransferase was used to demonstrate that the cellular nitrogen status indicators, PII and PII-UMP, probably bind in the central regulatory domain to stimulate the adenylylation and deadenylylation reactions, respectively. In the light of these results, intramolecular signaling within adenylyltransferase is discussed. 相似文献
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A nonimmune phagemid recombinant antibody fragment (rFab) library was generated with a nominal diversity of 1.16 x 10(7) using the QuikChange Multi Site-Directed Mutagenesis kit. Two degenerate primers spanning the third complementarity-determining region (CDR) loops of the antibody fragment light and heavy chain were mutated such that eight or nine amino acids were randomly changed per CDR loop. Seven proteins were used to evaluate the library quality. Protein-specific rFab antibodies were selected after three panning cycles. From 12% to 64% of the randomly selected colonies produced positive ELISA signals to the phagemid rFabs. Multisite-directed mutagenesis allowed a diverse rFab library to be rapidly constructed while retaining the structural framework of a Fab that had been optimized for production in Escherichia coli. 相似文献
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Collaborative and in-house laboratory trials were conducted to evaluate Cryptosporidium oocyst and Giardia cyst recoveries from source and finished-water samples by utilizing the Filta-Max system and U.S. Environmental Protection Agency (EPA) methods 1622 and 1623. Collaborative trials with the Filta-Max system were conducted in accordance with manufacturer protocols for sample collection and processing. The mean oocyst recovery from seeded, filtered tap water was 48.4% +/- 11.8%, while the mean cyst recovery was 57.1% +/- 10.9%. Recovery percentages from raw source water samples ranged from 19.5 to 54.5% for oocysts and from 46.7 to 70.0% for cysts. When modifications were made in the elution and concentration steps to streamline the Filta-Max procedure, the mean percentages of recovery from filtered tap water were 40.2% +/- 16.3% for oocysts and 49.4% +/- 12.3% for cysts by the modified procedures, while matrix spike oocyst recovery percentages ranged from 2.1 to 36.5% and cyst recovery percentages ranged from 22.7 to 68.3%. Blinded matrix spike samples were analyzed quarterly as part of voluntary participation in the U.S. EPA protozoan performance evaluation program. A total of 15 blind samples were analyzed by using the Filta-Max system. The mean oocyst recovery percentages was 50.2% +/- 13.8%, while the mean cyst recovery percentages was 41.2% +/- 9.9%. As part of the quality assurance objectives of methods 1622 and 1623, reagent water samples were seeded with a predetermined number of Cryptosporidium oocysts and Giardia cysts. Mean recovery percentages of 45.4% +/- 11.1% and 61.3% +/- 3.8% were obtained for Cryptosporidium oocysts and Giardia cysts, respectively. These studies demonstrated that the Filta-Max system meets the acceptance criteria described in U.S. EPA methods 1622 and 1623. 相似文献
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