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41.
Tropomyosin (Tm) is a coiled-coil protein that binds to filamentous actin (F-actin) and regulates its interactions with actin-binding proteins like myosin by moving between three positions on F-actin (the blocked, closed, and open positions). To elucidate the molecular details of Tm flexibility in relation to its binding to F-actin, we conducted extensive molecular dynamics simulations for both Tm alone and Tm-F-actin complex in the presence of explicit solvent (total simulation time >400 ns). Based on the simulations, we systematically analyzed the local flexibility of the Tm coiled coil using multiple parameters. We found a good correlation between the regions with high local flexibility and a number of destabilizing regions in Tm, including six clusters of core alanines. Despite the stabilization by F-actin binding, the distribution of local flexibility in Tm is largely unchanged in the absence and presence of F-actin. Our simulations showed variable fluctuations of individual Tm periods from the closed position toward the open position. In addition, we performed Tm-F-actin binding calculations based on the simulation trajectories, which support the importance of Tm flexibility to Tm-F-actin binding. We identified key residues of Tm involved in its dynamic interactions with F-actin, many of which have been found in recent mutational studies to be functionally important, and the rest of which will make promising targets for future mutational experiments. 相似文献
42.
Spijkerman E Barua D Gerloff-Elias A Kern J Gaedke U Heckathorn SA 《Extremophiles : life under extreme conditions》2007,11(4):551-562
Chlamydomonas acidophila faces high heavy-metal concentrations in acidic mining lakes, where it is a dominant phytoplankton species. To investigate
the importance of metals to C. acidophila in these lakes, we examined the response of growth, photosynthesis, cell structure, heat-shock protein (Hsp) accumulation,
and metal adsorption after incubation in metal-rich lake water and artificial growth medium enriched with metals (Fe, Zn).
Incubation in both metal-rich lake water and medium caused large decreases in photosystem II function (though no differences
among lakes), but no decrease in growth rate (except for medium + Fe). Concentrations of small Hsps were higher in algae incubated
in metal-rich lake-water than in metal-enriched medium, whereas Hsp60 and Hsp70A were either less or equally expressed. Cellular
Zn and Fe contents were lower, and metals adsorbed to the cell surface were higher, in lake-water-incubated algae than in
medium-grown cells. The results indicate that high Zn or Fe levels are likely not the main or only contributor to the low
primary production in mining lakes, and multiple adaptations of C. acidophila (e.g., high Hsp levels, decreased metal accumulation) increase its tolerance to metals and permit survival under such adverse
environmental conditions. Supposedly, the main stress factor present in the lake water is an interaction between low P and
high Fe concentrations. 相似文献
43.
Maan Barua 《The journal of the Royal Anthropological Institute》2022,28(3):896-919
Through an ethnography of parakeets and other denizens in London, this article expounds the concept of the feral and foregrounds its purchase for an anthropological inquiry into urban life. Ecological, cultural, and political connotations of ferality impinge upon evaluations of what counts and is allowed to flourish as metropolitan nature. Ferality is constructed through nativist and racial taxonomies which promote a biopolitics of eradicating parakeets. At the same time, parakeets trigger new ‘recombinant' ecological associations when they enter into relations with other avian life. They also foster affective alignments with people that create possibilities for a more just politics of dwelling. The feral recasts London's metropolitan nature as postcolonial and opens up novel ways of doing urban anthropology. 相似文献
44.
Tropomyosin (Tm) is a coiled-coil protein that binds to filamentous actin (F-actin) and regulates its interactions with actin-binding proteins like myosin by moving between three positions on F-actin (the blocked, closed, and open positions). To elucidate the molecular details of Tm flexibility in relation to its binding to F-actin, we conducted extensive molecular dynamics simulations for both Tm alone and Tm-F-actin complex in the presence of explicit solvent (total simulation time >400 ns). Based on the simulations, we systematically analyzed the local flexibility of the Tm coiled coil using multiple parameters. We found a good correlation between the regions with high local flexibility and a number of destabilizing regions in Tm, including six clusters of core alanines. Despite the stabilization by F-actin binding, the distribution of local flexibility in Tm is largely unchanged in the absence and presence of F-actin. Our simulations showed variable fluctuations of individual Tm periods from the closed position toward the open position. In addition, we performed Tm-F-actin binding calculations based on the simulation trajectories, which support the importance of Tm flexibility to Tm-F-actin binding. We identified key residues of Tm involved in its dynamic interactions with F-actin, many of which have been found in recent mutational studies to be functionally important, and the rest of which will make promising targets for future mutational experiments. 相似文献
45.
Adayev T El-Sherif Y Barua M Penington NJ Banerjee P 《Journal of neurochemistry》1999,72(4):1489-1496
Previous studies have indicated that stimulation of neuronal inhibitory receptors, such as the serotonin1A receptor (5-HT1A-R), could cause attenuation of the activity of both N-type Ca2+ channels and N-methyl-D-aspartic acid receptors, thus resulting in protection of neurons against excitotoxicity. The purpose of this study was to investigate if the 5-HT1A-R is also coupled to an alternative pathway that culminates in suppression of apoptosis even in cells that are deficient in Ca2+ channels. Using a hippocampal neuron-derived cell line (HN2-5) that is Ca2+ channel-deficient, we demonstrate here that an alternative pathway is responsible for 5-HT1A-R-mediated protection of these cells from anoxia-triggered apoptosis, assessed by deoxynucleotidyl-transferase-mediated dUTP nick end-labeling (TUNEL). The 5-HT1A-R agonist-evoked protection was eliminated in the presence of pertussis toxin and also required phosphorylation-mediated activation of mitogen-activated protein kinase (MAPK), as evidenced by the elimination of the agonist-elicited rescue of neuronal cells by the MAPK kinase inhibitor PD98059 but not by the phosphatidylinositol 3-kinase (PI-3K) inhibitor wortmannin. Furthermore, agonist stimulation of the 5-HT1A-R caused a 60% inhibition of anoxia-stimulated caspase 3-like activity in the HN2-5 cells, and this inhibition was abrogated by PD98059 but not by wortmannin. Although agonist stimulation of the 5-HT1A-R caused an activation of PI-3Kgamma in HN2-5 cells, our results showed that this PI-3Kgamma activity was not linked to the 5-HT1A-R-promoted regulation of caspase activity and suppression of apoptosis. Thus, in the neuronal HN2-5 cells, agonist binding to the 5-HT1A-R results in MAPK-mediated inhibition of a caspase 3-like enzyme and a 60-70% suppression of anoxia-induced apoptosis through a Ca2+ channel-independent pathway. 相似文献
46.
Murphy PA Barua K Hauck CC 《Journal of chromatography. B, Analytical technologies in the biomedical and life sciences》2002,777(1-2):129-138
Acetonitrile is superior to acetone, ethanol and methanol in extracting the 12 phytoestrogenic soy isoflavone forms found in foods. At 53% organic solvent in water, raw soy flour, tofu, tempeh, textured vegetable protein and soy germ were evaluated for isoflavone extraction efficiency. The efficiency of acetonitrile extraction was demonstrated in mass balance evaluations of toasting of soy flour and soymilk heating. 相似文献
47.
Umesh C. Pandey Ashok K. Singhal Nabin C. Barua R.P. Sharma Jogendra N. Baruah Kinzo Watanabe Palaniappan Kulanthaivel Werner Herz 《Phytochemistry》1984,23(2):391-397
Extraction of Conyza japonica gave strictic acid, ent-2β-hydroxy-15,16-epoxy-3,13(16),14-clerodatrien-18-oic acid and 5,7-dihydroxy-3,8,4′-trimethoxyflavone. Extraction of Grangea maderaspatana gave (-)-hardwickiic acid, ent-15,16-epoxy-1,3,13(16),14-clerodatetraen-18-oic acid and 3-hydroxy-8-acetoxypentadeca-1,9,14-trien-4,6-diyne. The structure of ent-2β-hydroxy-15,16-epoxy-3,13(16),14-cleroclatrien-18-oic acid was deduced by spectroscopic methods and by partial synthesis from (-)-hardwickiic acid and the stereochemistries of strictic acid and (ent-15,16-epoxy-1,3,13(16),14-clerodatraen-18-oic acid were established by correlation with ent-2β-hydroxy-15,16-epoxy-3,13(16),14-clerodatrien-18-oic acid. 相似文献
48.
Molecular mapping of genes determining height, time to heading, and growth habit in barley (Hordeum vulgare). 总被引:5,自引:0,他引:5
U M Barua K J Chalmers W T Thomas C A Hackett V Lea P Jack B P Forster R Waugh W Powell 《Génome》1993,36(6):1080-1087
A combination of random amplified polymorphic DNA (RAPD) and restriction fragment length polymorphism (RFLP) markers has been used to locate genes controlling important developmental characters in barley. The denso dwarfing gene has been mapped to the long arm of chromosome 3H. Stepwise multiple regression was also used to identify another region of the barley genome (on chromosome 7H), which contributed to variation in height. The denso locus was shown to be associated with delaying time to heading. A protein (WSP2) and an RAPD marker on barley chromosomes 5H and 6H, respectively, were also associated with time to heading. These results are discussed in relation to the genetic analysis of developmentally important traits and the development of dwarfing genes in barley breeding programs. 相似文献
49.
This study investigated the levels, trends and determinants of contraceptive use-failure in Matlab, Bangladesh, using a set of prospective data on 25,960 women of reproductive age. The data were extracted from the Record Keeping System (RKS) of Matlab for the period 1978-94. If there was any live birth during the use or within 7 months after the discontinuation of use, it was considered as a failure. The life table technique and hazard model were used as analytical tools. The results suggest that use-failure for pills, IUDs (TCu 200) and injectables and other temporary methods increased from 1978 to 1988, but began to decline after 1988. The cumulative probability of first-method failure within 1 year of method acceptance of the cohort of 1990-94 acceptors was 12.9% for pills, 2.0% for IUDs, 0.5% for injectables, 22.0% for condoms and 13.4% for 'other' methods (sampoon, foam, jelly and traditional methods). For pills, condoms and 'other' methods, the likelihood of failure declined with the duration of use; by contrast, the probability of an IUD failure increased over time, peaking at 3 years of use. The injectables maintained a low likelihood of failure regardless of the duration of use. The quality of Community Health Workers' (CHWs) performance was associated with the risk of failure of all temporary methods except condoms; women's background characteristics associated with failure varied by method. The effect of the quality of the CHWs' performance and the background variables on failure did not change much over time. It is felt that contraceptive failure deserves the serious attention of programme managers and policy makers to make the Bangladesh national family planning programme more successful. 相似文献
50.