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排序方式: 共有731条查询结果,搜索用时 15 毫秒
721.
This study was undertaken to investigate whether chondroitin sulfate (CS) can be efficiently isolated from broiler chicken by-product from mechanical deboning (BMD), which is a mixture of crushed bone, cartilage, skin, adipose tissue and muscle. With BMD as a starting material, it may be possible to maximize CS production from chicken cartilage. CS was liberated from BMD by proteolysis using proteolytic activities from papain, pancreatin, kiwi fruits and flavourzyme. The final product isolated by anion-exchange chromatography and differential precipitation with varying concentrations of ethanol contained CS-peptides with glucuronosyl-N-acetylgalactosamine-4-sulfate as a predominant disaccharide. All the enzyme sources used had sufficient activities to produce CS-peptides with undetectable amount of glucosamine. However, the size of peptide attaching to CS chain and the antigenicity to anti-keratan sulfate (KS) monoclonal antibody varied among the CS-peptides prepared with different proteinases. Papain digestion resulted in the smallest size of peptide with no detectable antigenicity to the anti-KS antibody. In contrast, pancreatin digestion provided CS-peptide having a very weak but positive antigenicity to the anti-KS antibody, which was much lower than that seen with CS-peptide prepared with kiwi fruit proteinase or flavourzyme. Pancreatin is suggested as an economical source of proteinase to liberate CS-peptides from BMD. 相似文献
722.
Christopher Rosin Mirko Erlkamp Julian?von?der Ecken Stefan Raunser Roland Winter 《Biophysical journal》2014,107(12):2982-2992
Actin is the main component of the microfilament system in eukaryotic cells and can be found in distinct morphological states. Global (G)-actin is able to assemble into highly organized, supramolecular cellular structures known as filamentous (F)-actin and bundled (B)-actin. To evaluate the structure and stability of G-, F-, and B-actin over a wide range of temperatures and pressures, we used Fourier transform infrared spectroscopy in combination with differential scanning and pressure perturbation calorimetry, small-angle x-ray scattering, laser confocal scanning microscopy, and transmission electron microscopy. Our analysis was designed to provide new (to our knowledge) insights into the stabilizing forces of actin self-assembly and to reveal the stability of the actin polymorphs, including in conditions encountered in extreme environments. In addition, we sought to explain the limited pressure stability of actin self-assembly observed in vivo. G-actin is not only the least temperature-stable but also the least pressure-stable actin species. Under abyssal conditions, where temperatures as low as 1–4°C and pressures up to 1 kbar are reached, G-actin is hardly stable. However, the supramolecular assemblies of actin are stable enough to withstand the extreme conditions usually encountered on Earth. Beyond ∼3–4 kbar, filamentous structures disassemble, and beyond ∼4 kbar, complete dissociation of F-actin structures is observed. Between ∼1 and 2 kbar, some disordering of actin assemblies commences, in agreement with in vivo observations. The limited pressure stability of the monomeric building block seems to be responsible for the suppression of actin assembly in the kbar pressure range. 相似文献
723.
Steffi Gaebler‐Schwarz Andrew Davidson Philipp Assmy Jixin Chen Joachim Henjes Eva‐Maria Nöthig Mirko Lunau Linda K. Medlin 《Journal of phycology》2010,46(5):1006-1016
Few members of the well‐studied marine phytoplankton taxa have such a complex and polymorphic life cycle as the genus Phaeocystis. However, despite the ecological and biogeochemical importance of Phaeocystis blooms, the life cycle of the major bloom‐forming species of this genus remains illusive and poorly resolved. At least six different life stages and up to 15 different functional components of the life cycle have been proposed. Our culture and field observations indicate that there is a previously unrecognized stage in the life cycle of P. antarctica G. Karst. This stage comprises nonmotile cells that range in size from ~4.2 to 9.8 μm in diameter and form aggregates in which interstitial spaces between cells are small or absent. The aggregates (hereafter called attached aggregates, AAs) adhere to available surfaces. In field samples, small AAs, surrounded by a colony skin, adopt an epiphytic lifestyle and adhere in most cases to setae or spines of diatoms. These AAs, either directly or via other life stages, produce the colonial life stage. Culture studies indicate that bloom‐forming, colonial stages release flagellates (microzoospores) that fuse and form AAs, which can proliferate on the bottom of culture vessels and can eventually reform free‐floating colonies. We propose that these AAs are a new stage in the life cycle of P. antarctica, which we believe to be the zygote, thus documenting sexual reproduction in this species for the first time. 相似文献
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726.
Thermophilic microorganisms as well as acetogenic bacteria are both considered ancient. Interestingly, only a few species of bacteria, all belonging to the family Thermoanaerobacteraceae, are described to conserve energy from acetate formation with hydrogen as electron donor and carbon dioxide as electron acceptor. This review reflects the metabolic differences between Moorella spp., Thermoanaerobacter kivui and Thermacetogenium phaeum, with focus on the biochemistry of autotrophic growth and energy conservation. The potential of these thermophilic acetogens for biotechnological applications is discussed briefly.
相似文献727.
728.
Israel M. Scott Gabe M. Rubinstein Gina L. Lipscomb Mirko Basen Gerrit J. Schut Amanda M. Rhaesa W. Andrew Lancaster Farris L. Poole II Robert M. Kelly Michael W. W. Adams 《Applied and environmental microbiology》2015,81(20):7339-7347
Caldicellulosiruptor bescii grows optimally at 78°C and is able to decompose high concentrations of lignocellulosic plant biomass without the need for thermochemical pretreatment. C. bescii ferments both C5 and C6 sugars primarily to hydrogen gas, lactate, acetate, and CO2 and is of particular interest for metabolic engineering applications given the recent availability of a genetic system. Developing optimal strains for technological use requires a detailed understanding of primary metabolism, particularly when the goal is to divert all available reductant (electrons) toward highly reduced products such as biofuels. During an analysis of the C. bescii genome sequence for oxidoreductase-type enzymes, evidence was uncovered to suggest that the primary redox metabolism of C. bescii has a completely uncharacterized aspect involving tungsten, a rarely used element in biology. An active tungsten utilization pathway in C. bescii was demonstrated by the heterologous production of a tungsten-requiring, aldehyde-oxidizing enzyme (AOR) from the hyperthermophilic archaeon Pyrococcus furiosus. Furthermore, C. bescii also contains a tungsten-based AOR-type enzyme, here termed XOR, which is phylogenetically unique, representing a completely new member of the AOR tungstoenzyme family. Moreover, in C. bescii, XOR represents ca. 2% of the cytoplasmic protein. XOR is proposed to play a key, but as yet undetermined, role in the primary redox metabolism of this cellulolytic microorganism. 相似文献
729.
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730.
Mirko Trutnau Mike Petzold Lysann Mehlig Martin Eschenhagen Katja Geipel Susann M��ller Thomas Bley Isolde R?ske 《Bioprocess and biosystems engineering》2011,34(3):287-295
Modelling of activated sludge processes is a commonly used technique to design and optimize wastewater treatment processes.
Since wastewater and activated sludge is characterized by chemical oxygen demand (COD) measurements, units of state variables
describing organic matter are expressed as equivalent amounts of COD. However, current procedures for measuring it have several
drawbacks, including the production of hazardous wastes, so the utility of other variables for characterizing the organic
load in modelling, such as total organic carbon (TOC), warrant re-evaluation. Other advantages of TOC over COD are that it
provides matrix-independent analytical results and it can be readily measured online. Proposals for TOC-based models were
made in the 1990s, but they seem to have sunk into obscurity. To re-assess the value of TOC for this purpose, we have recalculated
the EAWAG module for Bio-P removal coupled to the Activated Sludge Model No. 3 on a TOC basis, and tested it against data
acquired in batch experiments with four single carbon sources (acetate, glucose, citrate and casein). The batch test-based
calibrations showed a good match with experimental data, following modifications of the model to account for the anaerobic
volumes and retention times applied in the tests. 相似文献