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C. Brown D. F. R. P. Burslem J. B. Illian L. Bao W. Brockelman M. Cao L. W. Chang H. S. Dattaraja S. Davies C. V. S. Gunatilleke I. A. U. N. Gunatilleke J. Huang A. R. Kassim J. V. LaFrankie J. Lian L. Lin K. Ma X. Mi A. Nathalang S. Noor P. Ong R. Sukumar S. H. Su I. F. Sun H. S. Suresh S. Tan J. Thompson M. Uriarte R. Valencia S. L. Yap W. Ye R. Law 《Proceedings. Biological sciences / The Royal Society》2013,280(1764)
Neutral and niche theories give contrasting explanations for the maintenance of tropical tree species diversity. Both have some empirical support, but methods to disentangle their effects have not yet been developed. We applied a statistical measure of spatial structure to data from 14 large tropical forest plots to test a prediction of niche theory that is incompatible with neutral theory: that species in heterogeneous environments should separate out in space according to their niche preferences. We chose plots across a range of topographic heterogeneity, and tested whether pairwise spatial associations among species were more variable in more heterogeneous sites. We found strong support for this prediction, based on a strong positive relationship between variance in the spatial structure of species pairs and topographic heterogeneity across sites. We interpret this pattern as evidence of pervasive niche differentiation, which increases in importance with increasing environmental heterogeneity. 相似文献
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It has been over 80 years since the antiarthritic properties of gold(I) complexes were first recognized. However, a detailed understanding of their mechanism of action has been slow to develop. One likely biological target of gold(I) is the cathepsin family of lysosomal cysteine proteases, enzymes involved in the inflammation and joint destruction that are hallmarks of rheumatoid arthritis (RA). We have previously shown that analogs of auranofin, a clinically available antiarthritic drug, inhibit cathepsin B. In this study, the extent to which the steric and electronic properties of the phosphine ligand can be modified to obtain enhanced potency against cathepsin B is investigated. 相似文献
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Shamila S. Gunatilleke Cesar Augusto F. de Oliveira J. Andrew McCammon Amy M. Barrios 《Journal of biological inorganic chemistry》2008,13(4):555-561
Gold(I) compounds have been used in the treatment of rheumatoid arthritis for over 80 years, but the biological targets and
the structure–activity relationships of these drugs are not well understood. Of particular interest is the molecular mechanism
behind the antiarthritic activity of the orally available drug triethylphosphine(2,3,4,6-tetra-O-acetyl-β-1-d-thiopyranosato-S) gold(I) (auranofin, Ridaura). The cathepsin family of lysosomal, cysteine-dependent enzymes is an attractive biological
target of Au(I) and is inhibited by auranofin and auranofin analogs with reasonable potency. Here we employ a combination
of experimental and computational investigations into the effect of changes in the phosphine ligand of auranofin on its in
vitro inhibition of cathepsin B. Sequential replacement of the ethyl substituents of triethylphosphine by phenyl groups leads
to increasing potency in the resultant Au(I) complexes, due in large part to favorable interactions of the more sterically
bulky Au(I)–PR3 fragments with the enzyme active site. 相似文献
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B Utete C Phiri SS Mlambo N Maringapasi N Muboko TB Fregene 《African Journal of Aquatic Science》2018,43(1):1-15
Concentrations of aluminium, cadmium, chromium, cobalt, copper, iron, lead, nickel and zinc were determined in surface water, benthic sediments, and the gills, liver and stomach muscle tissues of Oreochromis niloticus and Clarias gariepinus in peri-urban lakes Chivero and Manyame, Zimbabwe. Five sites were sampled in each lake once per month in November 2015, February, May, August and November 2016. Pollution load index detected no metal contamination, whereas the geo-accumulation index reflected heavy to extreme sediment pollution, with Fe, Cd, Zn, Cr, Ni and Cu present in both lakes. Significant spatial temporal variations were detected for Al, Cr, Cu and Pb across sites within and between the two lakes. High Fe, Al and Cr concentrations in water and sediments in lakes Chivero and Manyame derive from geogenic background sources in addition to anthropogenic loads and intensity. Elevated concentrations of Al, Pb, Cu, Cd, Fe and Zn detected in gills, liver and stomach tissue of catfish corroborate concentrations in water and sediments, and pose the highest ecological and health risk for hydrobionts in lakes Chivero and Manyame. Contiguity of peri-urban lakes exposes them to similar threats, necessitating creative water management strategies, which ensure ecological continuity. 相似文献
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Baldeck C. A. Kembel S. W. Harms K. E. Yavitt J. B. John R. Turner B. L. Madawala S. Gunatilleke N. Gunatilleke S. Bunyavejchewin S. Kiratiprayoon S. Yaacob A. Supardi M. N. N. Valencia R. Navarrete H. Davies S. J. Chuyong G. B. Kenfack D. Thomas D. W. Dalling J. W. 《Oecologia》2016,182(2):547-557
Oecologia - While the importance of local-scale habitat niches in shaping tree species turnover along environmental gradients in tropical forests is well appreciated, relatively little is known... 相似文献