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61.
Oligogalacturonic acids (OGAs), derived from plant cell wall pectin, have
been implicated in a number of signal transduction pathways involved in
growth, development and defense responses of higher plants. This study
investigates the size range of OGAs capable of inducing ethylene synthesis
in tomato plants, and demonstrates that in contrast with many other
effects, only short chain OGAs are active. Oligomers across a range of DP
from 2-15 were separated and purified to homogeneity by QAE-Sephadex anion
exchange chromatography using a novel elution system. The OGAs were applied
to tomato plants and assayed for their ability to induce ethylene gas
release and changes in steady state levels of mRNA encoding the ethylene
forming enzyme aminocyclopropane-1-carboxylic acid oxidase (ACO). The study
demonstrated that only OGAs in the size range of DP4-6 were active both in
eliciting ACO expression and in the production of ethylene.
相似文献
62.
Fluorene Oxidation In Vivo by Phanerochaete chrysosporium and In Vitro during Manganese Peroxidase-Dependent Lipid Peroxidation 总被引:2,自引:1,他引:1
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The oxidation of fluorene, a polycyclic hydrocarbon which is not a substrate for fungal lignin peroxidase, was studied in liquid cultures of Phanerochaete chrysosporium and in vitro with P. chrysosporium extracellular enzymes. Intact fungal cultures metabolized fluorene to 9-hydroxyfluorene via 9-fluorenone. Some conversion to more-polar products was also observed. Oxidation of fluorene to 9-fluorenone was also obtained in vitro in a system that contained manganese(II), unsaturated fatty acid, and either crude P. chrysosporium peroxidases or purified recombinant manganese peroxidase. The oxidation of fluorene in vitro was inhibited by the free-radical scavenger butylated hydroxytoluene but not by the lignin peroxidase inhibitor NaVO(inf3). Manganese(III)-malonic acid complexes could not oxidize fluorene. These results indicate that fluorene oxidation in vitro was a consequence of lipid peroxidation mediated by P. chrysosporium manganese peroxidase. The rates of fluorene and diphenylmethane disappearance in vitro were significantly faster than those of true polycyclic aromatic hydrocarbons or fluoranthenes, whose rates of disappearance were ionization potential dependent. This result indicates that the initial oxidation of fluorene proceeds by mechanisms other than electron abstraction and that benzylic hydrogen abstraction is probably the route for oxidation. 相似文献
63.
Declan P. Bogan Richard O'Kennedy 《Journal of chromatography. B, Analytical technologies in the biomedical and life sciences》1996,686(2):95
A HPLC method was developed for the determination of the metabolites of coumarin and 7-hydroxycoumarin in plasma and serum. Separation was based on gradient elution of 7-hydroxycoumarin glucuronide, 7-hydroxycoumarin, coumarin and finally 4-hydroxycoumarin (which is used as an internal standard). Standards, prepared in plasma or serum, and samples were treated with trichloroacetic acid, mixed and centrifuged. The supernatant was removed and analyzed by reversed-phase high-performance liquid chromatography on a C18 column. The limit of detection was 50 ng/ml for 7-hydroxycoumarin and 200 ng/ml for coumarin and 7-hydroxycoumarin glucuronide. The linear range was 0.5–100 μg/ml for each of the analytes. The percentage relative standard deviation about the mean measured concentrations were all below 10%. There was no statistical difference between the standard curves prepared in plasma or serum. The method developed was applied to the determination of each of the three compounds in serum, after the administration of 7-hydroxycoumarin, and in plasma after the administration of coumarin. The concentrations of total 7-hydroxycoumarin in the serum samples were also determined by another HPLC method and the results were compared. There was no statistical difference between the results determined. 相似文献
64.
A change in twist of actin provides the force for the extension of the acrosomal process in limulus sperm: the false-discharge reaction 总被引:6,自引:5,他引:1
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One of the most spectacular motions is the generation of the acrosomal process in the limulus sperm. On contact with the egg, the sperm generates a 60-mum-long process that literally drills its way through the jelly surrounding the egg. This irresversible reaction takes only a few seconds. We suggested earlier that this motion is driven by a change in twist of the actin filaments comprising the acrosomal process. In this paper we analyze the so-called false discharge, a reversible reaction, in which the acrosomal filament bundle extends laterally from the base of the sperm and not anteriorly from the apex. Unlike the true discharge, which is straight, the false discharge is helical. Before extension, the filament bundle is coiled about the base of the sperm. In the coil, the bundle is not smoothly bent but consists of arms (straight segments) and elbows (corners) so that the coil looks like a 14-sided polygon. The extension of the false discharge works as follows: starting at the base of the bundle, the filaments change their twist which concomitantly changes the orientations of the elbows relative to each other; that is, in the coil, the elbows all like in a common plane, but after the change in twist, the plane of each elbow is rotated to be perpendicular to that of its neighbors. This change transforms the bundle from a compact coil into an extended left- handed helix. Because the basal end of the bundle is unconstrained, the extension is lateral. The true discharge works the same way but starts at the apical end of the bundle. The apical end, however, is constrained by its passage through the nuclear canal, which directs the extention anteriorly. Unlike the false discharge, during the true discharge the elbows are melted out, making the reaction irreversible. This study shows that rapid movement can be regenerated by actin without myosin and gives us insight into the molecular mechanism. 相似文献
65.
A species from Lake Poso, Indonesia represents the first instance of cementation in the freshwater bivalve family Corbiculidae.
Posostrea anomioides gen. nov., sp. nov., which is cemented indifferently by its left or right valve to calcareous rocks,
reaches a size of 16 mm. It has typical corbiculoid dentition, with serrated lateral teeth, and juveniles are brooded primarily
in the inner ctenidia. Lake Poso occupies a tectonic fault in central Sulawesi. Posostrea adds to an interesting radiation
of endemic fishes and molluscs, including the gastropod genera Miratesta and Tylomelania.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
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Kline Christopher E. Zielinski Mark R. Devlin Tina M. Kripke Daniel F. Bogan Richard K. Youngstedt Shawn D. 《Sleep and biological rhythms》2010,8(1):42-51
Sleep and Biological Rhythms - Although self-reported long sleep is associated with increased morbidity and mortality, little is known about the objective sleep patterns and daytime functioning of... 相似文献
70.