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101.
102.
J Ralph C Lapierre J M Marita H Kim F Lu R D Hatfield S Ralph C Chapple R Franke M R Hemm J Van Doorsselaere R R Sederoff D M O'Malley J T Scott J J MacKay N Yahiaoui A Boudet M Pean G Pilate L Jouanin W Boerjan 《Phytochemistry》2001,57(6):993-1003
Studying lignin-biosynthetic-pathway mutants and transgenics provides insights into plant responses to perturbations of the lignification system, and enhances our understanding of normal lignification. When enzymes late in the pathway are downregulated, significant changes in the composition and structure of lignin may result. NMR spectroscopy provides powerful diagnostic tools for elucidating structures in the difficult lignin polymer, hinting at the chemical and biochemical changes that have occurred. COMT (caffeic acid O-methyl transferase) downregulation in poplar results in the incorporation of 5-hydroxyconiferyl alcohol into lignins via typical radical coupling reactions, but post-coupling quinone methide internal trapping reactions produce novel benzodioxane units in the lignin. CAD (cinnamyl alcohol dehydrogenase) downregulation results in the incorporation of the hydroxycinnamyl aldehyde monolignol precursors intimately into the polymer. Sinapyl aldehyde cross-couples 8-O-4 with both guaiacyl and syringyl units in the growing polymer, whereas coniferyl aldehyde cross-couples 8-O-4 only with syringyl units, reflecting simple chemical cross-coupling propensities. The incorporation of hydroxycinnamyl aldehyde and 5-hydroxyconiferyl alcohol monomers indicates that these monolignol intermediates are secreted to the cell wall for lignification. The recognition that novel units can incorporate into lignins portends significantly expanded opportunities for engineering the composition and consequent properties of lignin for improved utilization of valuable plant resources. 相似文献
103.
104.
Summary In dipteran insects the most distal telomere-associated DNA known to exist consists of long, complex tandem repeats. We have classified the 340-bp tandemly arranged repeats in Chironomus pallidivittatus. The repeats are distributed in a small number of subfamilies. One type of the repeat has the character of a master unit from which other main units can be derived usually by simple changes. The derived subfamilies contain segments that are degenerate versions of the corresponding segment in the master sequence. Such segments can also occur together in one and the same repeat unit in different combinations. There is a complete absence of subfamily-specific base variants in regions lying outside of the degenerate segments. Homogenization takes place between DNA sequences that are often smaller than a whole repeat unit. The mosaic structure of the repeat arrays suggests that gene conversion is an important force in the generation and maintenance of this family of repeats.Offprint requests to: M. Cohn 相似文献
105.
Treatment with SiO2 releases from peritoneal macrophages a soluble factor which stimulates the synthesis of collagen and other proteins in incubated slices of experimental granulation tissue. This factor can also be obtained by SiO2-treatment from certain subcellular particles of intact macrophages. A similar agent is released from the macrophages by incubation with rheumatoid synovialtissue extract. Macrophages induced by paraffin or thioglycollate medium cannot be stimulated further by SiO2. The SiO2-treated macrophages have no effect on detached matrix-free cells from embryonic-chick tendon or granulation tissue. Another factor from macrophages, present in the 100000 g-supernatant of the homogenate, inhibits the synthesis of collagen in granuloma slices. The synthesis of DNA and RNA in slices is suppressed by the extract from intact macrophages but not affected by preparations obtained with SiO2. The possible relevance of these findings to lysosomal actions, to the regulation of granuloma formation and to inflammation are discussed. 相似文献
106.
Cyclopeptine, a benzodiazepine alkaloid of Penicillium cyclopium, is formed from anthranilic acid, L-phenylalanine and the methyl group of L-methionine by cyclopeptine synthetase. The following partial activities of this enzyme system were determined in vitro: anthranilic acid and L-phenylalanine adenylyltransferase activity, binding of anthranilic acid and L-phenylalanine as thioesters to proteins, formation of thioester-bound N-methyl-L-phenylalanine and N-methyl-L-phenylalanylanthranilic acid. The obtained results indicate that cyclopeptine is formed via enzyme-bound intermediates by the thiotemplate mechanism of peptide biosynthesis. 相似文献
107.
Marita Bengtsson Johan Broddefalk Jan Dahmen Krister Henriksson Jan Kihlberg Hans Lonn B.R. Srinivasa Kristina Stenvall 《Glycoconjugate journal》1998,15(3):223-231
The 2-bromoethyl -glycosides of the disaccharide galabiose [Gal(1-4)Gal] and the trisaccharides globotriose [Gal(1-4)Gal(1-4)Glc] and 3-sialyllactose [Neu5Ac(2-3)Gal(1-4)Glc] have been prepared by improved routes. The 2-bromoethyl glycosides were then used in cesium carbonate promoted alkylations of the sulfhydryl groups of cysteine and homocysteine residues in T cell stimulating peptides. This convergent and general approach was used to prepare 16 neoglycopeptides which were obtained in 52–95% yields after purification by HPLC. 1H NMR spectroscopy revealed that -elimination and epimerization of neoglycopeptide stereocentres did not occur during the synthesis. 相似文献
108.
Maximilian Schultheiss Sven Schnichels Thoralf Hermann Jose Hurst Marita Feldkaemper Blanca Arango-Gonzalez Marius Ueffing Karl U. Bartz-Schmidt Guenther Zeck Martin S. Spitzer 《PloS one》2016,11(2)
Purpose
Hypothermia has been shown to be neuroprotective in the therapy of ischemic stroke in the brain. To date no studies exist on the level of the inner retina and it is unclear if hypothermia would prolong the ischemic tolerance time of retinal ganglion cells, which are decisive in many ischemic retinopathies.Methods
Bovine eyes were enucleated and stored either at 21°C or 37°C for 100 or 340 minutes, respectively. Afterwards the globes were dissected, the retina was prepared and either the spontaneous ganglion cell responses were measured or the retina was incubated as an organotypic culture for additional 24 hours. After incubation the retina was either processed for histology (H&E and DAPI staining) or real-time PCR (Thy-1 expression) was performed.Results
Hypothermia prolonged ganglion cell survival up to 340 minutes under ischemic conditions. In contrast to eyes kept at 37°C the eyes stored at 21°C still showed spontaneous ganglion cell spiking (56.8% versus 0%), a 5.8 fold higher Thy-1 mRNA expression (not significant, but a trend) and a preserved retinal structure after 340 minutes of ischemia.Conclusion
Hypothermia protects retinal ganglion cells against ischemia and prolongs their ischemic tolerance time. 相似文献109.
Harry Farmer Evan W. Carr Marita Svartdal Piotr Winkielman Antonia F. de C. Hamilton 《PloS one》2016,11(4)
The tendency to mimic the behaviour of others is affected by a variety of social factors, and it has been argued that such “mirroring” is often unconsciously deployed as a means of increasing affiliation during interpersonal interactions. However, the relationship between automatic motor imitation and status/power is currently unclear. This paper reports five experiments that investigated whether social status (Experiments 1, 2, and 3) or power (Experiments 4 and 5) had a moderating effect on automatic imitation (AI) in finger-movement tasks, using a series of different manipulations. Experiments 1 and 2 manipulated the social status of the observed person using an associative learning task. Experiment 3 manipulated social status via perceived competence at a simple computer game. Experiment 4 manipulated participants’ power (relative to the actors) in a card-choosing task. Finally, Experiment 5 primed participants using a writing task, to induce the sense of being powerful or powerless. No significant interactions were found between congruency and social status/power in any of the studies. Additionally, Bayesian hypothesis testing indicated that the null hypothesis should be favoured over the experimental hypothesis in all five studies. These findings are discussed in terms of their implications for AI tasks, social effects on mimicry, and the hypothesis of mimicry as a strategic mechanism to promote affiliation. 相似文献
110.
Daniel F. Alamidi Simon S. I. Kindvall Penny L. Hubbard Cristinacce Deirdre M. McGrath Simon S. Young Josephine H. Naish John C. Waterton Per Wollmer Sandra Diaz Marita Olsson Paul D. Hockings Kerstin M. Lagerstrand Geoffrey J. M. Parker Lars E. Olsson 《PloS one》2016,11(3)