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991.
Eriberta Nepomuceno Navera Koji Sode Eiichi Tamiya Isao Karube 《Biosensors & bioelectronics》1991,6(8):675-680
An enzyme sensor is developed using carbon fiber to measure acetylcholine concentration. The mechanism is based on the detection of H2O2 which is a product of the sequential enzyme reactions of acetylcholinesterase and choline oxidase. The fabrication of the electrode is described. The sensor is polarized at 1.2 V. Enzymes are co-immobilized in polyvinyl alcohol containing styryl pyrydinium (photo-crosslinkable polymer). A fast response time of 0.8 min is obtained. A linear correlation is observed between 0.2 and 1.0 mM. Other optimal operational conditions with respect to pH, temperature and stability are discussed. The use of carbon fiber containing co-immobilized enzymes could offer several model advantages especially in neuroscience research. In conclusion, the aims of the present work are centered on carbon fiber electrode fabrication, immobilization electrochemical measurements. 相似文献
992.
Madihah Md Salleh Liew Shiau Tsuey Arbakariya Bin Ariff 《Biotechnology and Bioprocess Engineering》2008,13(1):33-39
The profile of enzymes relevant to solvent production during direct fermentation of sago starch by Clostridium saccharobutylicum P262 in a 2 L stirred tank fermenter was determined utilizing different pH control strategies. During fermentation without
pH control (initial pH of 6), the specific activity of crotonase, thiolase, and β-hydroxybutyryl-CoA dehydrogenase increased
proportionally with solvent production. The highest crotonase (3,450.7 kat) and phosphotransbutyrylase activity (1,475.6 kat)
was observed in fermentation where pH was maintained at 5 during the acidogenic phase and corresponded to a fairly high acid
accumulation but low solvent production. During fermentation with a controlled pH of 5.25 during the sol-ventogenic phase,
the highest thiolase specific activity (255.7 kat) was obtained and corresponded to the highest production of acetone. On
the other hand, the highest specific activities of crotonase, β-hydroxybutyryl-CoA dehydrogenase, and phosphotransbutyrylase
were observed at pH 5.5 and corresponded to the highest production of ethanol and butanol. Butyryl-CoA dehydrogenase had no
significance role in solvent fermentation. These results suggested that pH control strategies were important for improvement
of solvent production during direct fermentation of sago starch by C. saccharobutylicum. 相似文献
993.
Bacillus licheniformis produced a water‐insoluble levan which has potential application as a selective plugging agent in microbial enhanced oil recovery (MEOR). The microorganism grew on sucrose, glucose, and fructose but produced levan only on sucrose. Plugging may thus be selectively controlled in the reservoir by substrate manipulation. B. licheniformis and a crude preparation of its extracellular enzymes were evaluated for their ability to produce levan under reservoir conditions. Oil reservoirs which have a temperature of less than 55°C, a pH between 6 and 9, a pressure less than 500 atm, and a salt concentration of 4% or less are potentially suitable. Examples of such reservoir conditions are found in Lloydminster on the Alberta‐Saskatchewan border, one of the largest Canadian oil reserves. 相似文献
994.
995.
O. UENO 《Plant, cell & environment》2004,27(5):627-639
The amphibious leafless sedge, Eleocharis baldwinii, expresses C4 characteristics in the terrestrial form and intermediate characteristics between C3 and C4 photosynthesis in the submerged form. This study examined the immunocytochemical localization of C3 and C4 enzymes in culms of the two forms to elucidate the regulatory mechanism of photosynthetic metabolism and compared the activities and amounts of C3 and C4 enzymes with those in other Eleocharis species, E. vivipara and E. retroflexa, which show C4 characteristics on land but C3 and C4 characteristics under water. The terrestrial form of E. baldwinii exhibited a C4‐like pattern of enzyme localization. The submerged form exhibited a modified anatomy with well‐developed mesophyll cells and small Kranz cells. The C4 enzyme levels declined conspicuously in outer mesophyll cells adjacent to the epidermis, whereas Rubisco levels increased throughout the mesophyll in the submerged form. These results suggest that intermediate photosynthesis between C3 and C4 photosynthesis in the submerged form results from the predominant operation of the C3 pathway in the outer mesophyll cells and the C4 pathway in both the inner mesophyll and Kranz cells. Differences in the degree of C4 expression in terrestrial forms of Eleocharis species may cause the differences in the expression of photosynthetic modes under water. 相似文献
996.
Reactive oxygen species (ROS) are of great importance in plant metabolism. However, uncontrolled activation of ROS might have deleterious effects in cells. Eleven Mediterranean countries are still under threat of an introduced taxon of Caulerpa racemosa var. cylindracea. In the present study, it has been aimed to compare the antioxidant status of this highly invasive alga with some Mediterranean macrophytes collected in the same habitat. For this purpose, such antioxidant enzyme activities as superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GSH-Px), and lipid peroxidation (LPO) as well, levels have been determined in C. racemosa, Cystoseira barbata C. Agardh, Padina pavonica (Linnaeus) Thivy and Enteromorpha sp. The highest SOD, CAT, GSH-Px enzyme activities and the lowest LPO level have been measured in the invasive C. racemosa. In conclusion, C. racemosa var. cylindracea seems more tolerant in warring with ROS than the Mediterranean species tested do. These results could partly explain the amazing success of C. racemosa var. cylindracea introduced in the Mediterranean. 相似文献
997.
D. Chakrabarty Y. H. Dewir E. J. Hahn S. K. Datta K. Y. Paek 《Plant Growth Regulation》2007,51(1):11-19
The present study investigated the dynamics of nutrient utilization and various growth and physiological parameters during
in vitro proliferation of apple root stock ‘M9 EMLA’ in two different bioreactor systems, i.e. temporary and continuous immersions.
Individual shoots obtained from temporary immersion system had higher dry mass and were of better quality than those obtained
from continuous immersion. In continuous immersion bioreactor, apple shoots appeared to utilize more nutrients from liquid
culture medium than that from temporary immersion. The shoot growth was limited by the availability of phosphate and nitrogen
in continuous immersion system. The shoots produced in temporary immersion bioreactor showed higher photosynthetic rate, maximum
quantum yield of photosystem-II and slow but steady rate of nutrient absorption, indicating the occurrence of higher photomixotrophic
metabolism. The study also showed that high level of antioxidant scavenging enzymes in shoots grown in continuous immersion
system induced physiological changes to foster adaptation to stresses. 相似文献
998.
The antioxidant response of four freshwater microalgal species, Chlorella vulgaris Beij., Scenedesmus platydiscus (G. M. Smith) Chod., Scenedesmus quadricauda(Turp.) Bréb., and Selenastrum capricornutum Printz without pyrene addition (control) and at two pyrene concentrations (0.1 and 1.0 mgL−1) were investigated. Under the control condition, the values of the antioxidant parameters differed significantly among species and the difference was seemed not to be related to their susceptibility to pyrene. The antioxidant response to pyrene treatments also varied from species to species. Pyrene led to a significant increase in total glutathione (GSH) content in all species except C. vulgaris, a species did not exhibit any ability to metabolize pyrene. The glutathione-S-transferase (GST) activities also remained unchanged in pyrene treated C. vulgaris, increased greatly in S. platydiscus and Se. capricornutum (the two species with higher pyrene metabolism ability), but inhibited remarkably in S. quadricauda (the only species sensitive to pyrene toxicity). On the other hand, the glutathione reductase (GR) activities increased in C. vulgaris but remained at a similar level as the control in the other three species. The malondialdehyde (MDA) content, an indicator of lipid peroxidation, declined in S. quadricauda but showed no significant change in the other three species. The activities of glutathione peroxidase (GPX), superoxide dismutase (SOD) and catalase (CAT) in pyrene treated cells remained almost the same as the controls for all microalgal species. Results suggested that the alterations of antioxidant systems in microalgae might not be useful indicators of pyrene exposure but pyrene-enhanced GSH metabolism might be important in pyrene biotransformation. 相似文献
999.
Sami Ahmad Michael A. Beilstein Ronald S. Pardini 《Archives of insect biochemistry and physiology》1989,12(1):31-49
In vertebrate species, cytotoxic H2O2 and other lipid or organic hydroperoxides (ROOH) formed in aerobic metabolism are removed by a selenoprotein, glutathione peroxidase (GPOX). The GPOX activity in most rat tissues ranges from 100 to 1,000 units (1 unit = 1 nmol NADPH oxidized·mg protein?1·min?1), except for muscles (20–30 units). In contrast, GPOX activities of two strains of the housefly (Musca domestica), cabbage looper (Trichoplusia ni), southern armyworm (Spodoptera eridania), and black swallowtail butterfly (Papilio polyxenes), were found to be in the range 2–12 units. Trivial GPOX activity was detected in the confused flour beetle (Tribolium confusum). In the earthworm (Lumbricus terrestris), banana slug (Ariolimax columbianus), and market squid (Loligo opalescens), the GPOX activity ranged from 1 to 5 units. Tissue selenium concentrations were about 500–1,000 ppb for adult M. domestica, 600 ppb in T. confusum, 32 ppb in T. ni, 17 ppb in S. eridania, and 31 ppb in P. polyxenes larvae. The form of selenium incorporated at such high levels in tissues of invertebrates such as M. domestica remains an unresolved issue. Peroxidase activity of non-selenium glutathione-S-transferase (GT) against ROOH may compensate for the low GPOX activity. Catalase (CAT) has high activity and wide subcellular distribution in insects. This may be an evolutionary adaptation to GT's inability to catalyze the reduction of H2O2. The GT's peroxidase and CAT activities were not assessed for other invertebrate species, and warrants an investigation due to their reported low GPOX levels. 相似文献
1000.
KIYOSHI AKEO HIROTOMO MIYAMOTO SHIGEKUNI OKISAKA TADAHISA HIRAMITSU 《Pigment cell & melanoma research》1999,12(3):199-205
Light-induced peroxidation of polyunsaturated fatty acids (PUFA) may generate lipid hydroperoxides, which may have toxic effects on retinal pigment epithelial (RPE) cells in vitro. We investigated the effects of cool-white fluorescent light on the RPE cells incubated with linoleic acids (LA) or linoleic acid hydroperoxides (LHP) and the influence of antioxidative enzymes. We measured the bovine RPE cell number after exposure to fluorescent light (610 and 1,200 lux) in the presence of LA or LHP. Furthermore, the effects of superoxide dismutase (SOD) and catalase on LA- or LHP-treated RPE cells were also examined. Both LA and LHP treatment increased RPE cell number under weak illumination (610 lux), but dose-dependently decreased the number of cells exposed to strong illumination (1,200 lux). With exposure to strong illumination, LA caused a greater reduction in RPE cell number than LHP. Multiple linear regression analysis showed that the number of RPE cells was significantly decreased in a manner dependent on the interactions of the illuminance of light and the concentrations of LA or LHP. The antioxidative enzymes significantly ameliorated the damage to RPE cells from LA or LHP and exposure to light. Therefore, the exposure to fluorescent light augmented the cytotoxic effects of LA and LHP on RPE cells, and this effect is likely to be mediated by reactive oxygen species. 相似文献