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31.
Regulation of D-alanine carboxypeptidase and peptidoglycan cross-linkage in amino acid-deprived Escherichia coli. 总被引:2,自引:2,他引:0
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The effect of amino acid deprivation on the activities of D-alanine carboxypeptidase (CPase) and peptidoglycan transpeptidase in Escherichia coli was determined. Enzymes were assayed in ether-treated bacteria (ETB) which were permeable to peptidoglycan nucleotide precursors. ETB were prepared at intervals from cultures grown in the presence and absence of a required amino acid. The specific activity of CPase in ETB decreased 50 to 85% during amino acid deprivation. This was paralleled by a 60 to 70% decrease in the specific activity of peptidoglycan transpeptidase. Both enzymes reached their lowest level of activity about 40 min after the onset of amino acid deprivation. The decrease in CPase activity apparently was not due to degradation of the enzyme, since full activity was restored after disruption of ETB by sonication. A decrease in CPase activity was associated with an enhancement of transpeptidation. The peptidoglycan synthesized in vitro by amino acid-deprived ETB was 1.7 times more cross-linked than the peptidoglycan synthesized by control ETB These results support the proposal that CPase may be involved in regulating transpeptidation in E. coli. 相似文献
32.
Determination of serum protein concentration in nanoliter blood samples using fluorescamine or 9-phthalaldehyde. 总被引:15,自引:0,他引:15
Fluorometric procedures were developed to permit measurement of total protein concentration in nanoliter serum samples, using either fluorescamine or o-phthalaldehyde. The sensitivities of assays using these two reagents were similar, but the o-phthalaldehyde method was found to be somewhat simpler and more reproducible. Accurate measurements could be obtained on serum samples of 4 to 5 nl with either reagent, by using a serum standard. Fluorescence differed considerably among individual serum proteins, albumin generally showing greater fluorescence than globulins. Small molecular weight species in serum did not contribute appreciably to total serum fluorescence with either reagent. 相似文献
33.
(1) 2,3-Diphosphoglyceric acid (2,3-DPG) is present in the erythrocytes (RBC) of the 68-day loggerhead turtle embryo and 44-day green sea turtle embryo at levels of 7.4 and 5.5 μmoles/ml of RBC, representing the major organic phosphate during the latter period of embryonic development. (2) Inositol pentaphosphate (IPP) is absent in the red blood cells of the embryos of both the loggerhead and green sea turtle. (3) Near equimolar amounts of 2,3-DPG and IPP are present in the erythrocytes of the adult loggerhead and green sea turtle. The total concentration of these two organic phosphates is approximately 0.75 μmoles/ml of RBC in the adult of both species. (4) There is a switch from embryonic to adult hemoglobin during development of these two species of turtles; the two embryonic bands have identical electrophoretic mobilities, whereas the two adult bands migrate differently on cellulose acetate at pH 8.6. (5) The whole blood oxygen affinity of the adult loggerhead and green sea turtle is 60.3 and 32.6 Torr, respectively. (6) The stripped adult hemoglobins in these two species of turtles show no change in oxygen affinity upon addition of 2,3-DPG, ATP, or IPP. (7) It therefore appears unlikely that whole blood oxygen affinity is controlled by organic phosphate modulation of hemoglobin function in these species of turtles. 相似文献
34.
35.
Agarose slab-gel electrophoresis equipment. 总被引:28,自引:0,他引:28
Simple slab-gel molds which utilize the electrophoresis apparatus described by F. W. Studier (J. Mol. Biol.79, 237 (1973)) have been designed for pouring and running agarose slab-gels. Analytical gels in which many samples are run simultaneously facilitate the assay of many enzymes which lead to physical changes in DNA, whereas the preparative gels allow the separation of large quantities (1–20 mg) of DNA fragments. 相似文献
36.
Raquel Santos Jorge Troy R. Hawkins Edgar G. Hertwich 《The International Journal of Life Cycle Assessment》2012,17(1):9-15
Purpose
The purpose of this study is to provide life cycle inventory data and results for components of electrical grids to the larger community of life cycle assessment practitioners. This article is the first in a series of two, each focusing on different components of power grids. In part 1, the objects under scope are power lines and cables. Systems for overhead, underground, and subsea transmission are modeled here, including HVDC systems used in long-distance transmission. 相似文献37.
38.
Joseph Tibbs Mohamed Ghoneim Colleen C Caldwell Troy Buzynski Wayne Bowie Elizabeth
M Boehm M
Todd Washington S
M
Ali Tabei Maria Spies 《Nucleic acids research》2021,49(9):e53
Molecular machines within cells dynamically assemble, disassemble and reorganize. Molecular interactions between their components can be observed at the single-molecule level and quantified using colocalization single-molecule spectroscopy, in which individual labeled molecules are seen transiently associating with a surface-tethered partner, or other total internal reflection fluorescence microscopy approaches in which the interactions elicit changes in fluorescence in the labeled surface-tethered partner. When multiple interacting partners can form ternary, quaternary and higher order complexes, the types of spatial and temporal organization of these complexes can be deduced from the order of appearance and reorganization of the components. Time evolution of complex architectures can be followed by changes in the fluorescence behavior in multiple channels. Here, we describe the kinetic event resolving algorithm (KERA), a software tool for organizing and sorting the discretized fluorescent trajectories from a range of single-molecule experiments. KERA organizes the data in groups by transition patterns, and displays exhaustive dwell time data for each interaction sequence. Enumerating and quantifying sequences of molecular interactions provides important information regarding the underlying mechanism of the assembly, dynamics and architecture of the macromolecular complexes. We demonstrate KERA’s utility by analyzing conformational dynamics of two DNA binding proteins: replication protein A and xeroderma pigmentosum complementation group D helicase. 相似文献
39.
Sahoo Kamalakanta Upadhyay Amit Runge Troy Bergman Richard Puettmann Maureen Bilek Edward 《The International Journal of Life Cycle Assessment》2021,26(1):189-213
The International Journal of Life Cycle Assessment - Producing biochar from forest residues can help resolve environmental issues by reducing forest fires and mitigating climate change. However,... 相似文献
40.
Troy J. Gibson Charles W. Mason Jade Y. Spence Heather Barker Neville G. Gregory 《Journal of applied animal welfare science : JAAWS》2013,16(3):222-238
Captive bolt stunning is used for rendering livestock insensible at slaughter. The mechanical factors relating to performance of 6 penetrating captive bolt gun (CBG) models were examined. The Matador Super Sécurit 3000 and the .25 Cash Euro Stunner had the highest kinetic energy values (443 J and 412 J, respectively) of the CBGs tested. Ninety percent (27/30) of CBGs held at a government gun repository (United Kingdom) were found to have performed at a normal standard for the model, while 53% (10/19) of commercial contractor CBGs tested were found to underperform for the gun model. When the .22 Cash Special was fired 500 times at 4 shots per min, the gun reached a peak temperature of 88.8°C after 2.05 hr. Repeat firing during extended periods significantly reduced the performance of the CBG. When deciding on the appropriate CBG/cartridge combination, the kinetic energy delivered to the head of the nonhuman animal, bolt penetration depth, and species/animal type must be considered. It is recommended that CBGs are routinely checked for wear to the bolt and barrel if they are repeatedly fired in a session. 相似文献