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A study was conducted on the adsorption of 45Ca2+ to a surface film of a hydrophobic protein derived from synaptic membranes isolated from bovine cerebellum. A kinetic analysis of Ca2+ displacement from the protein by various metal and organic cations could be described by a rate law based on diffusion and displacement. The relative rate constants for the displacement of bound Ca2+ were in the order Li+ <Na+, Rb+ <Cs+ <K+, NH4+. Among the alkaline earth series the sequence was Mg2+, Sr2+ <Ba2+. Ca2+ adsorption could be described by a theoretical formulation which takes into account an interfacial energy and potential barrier as well as the diffusional process. An attempt was made to consider the effect of energy of hydration of the cations, surface charge, and the chemical environment at the interface on catonic selectivity. The behavior of the cations in this system significantly resemble their behavior in natural membranes, particularly excitatory ones. The structural and physicochemical environment of the protein at the interface is discussed in relation to Ca2+ binding and cationic selectivity. 相似文献
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Jennifer J Beard David Evans Walter Peter G Allsopp 《Australian Journal of Entomology》2003,42(1):51-78
Abstract In many areas of the world, spider mites are significant pests of sugarcane. Australia is currently fortunate in lacking the most destructive species, and usually suffers only sporadic damage. Herein, we provide a key to the genera of spider mites associated with sugarcane, review the most significant genus, Oligonychus Berlese, and provide a key to the species of grass-feeding Oligonychus in the Australasian region. The species O. araneum Davis, O. digitatus Davis, O. grypus Baker and Pritchard, O. orthius Rimando, and O. oryzae (Hirst) are redescribed, while the Australian O. zanclopes sp. n. Beard and Walter from sugarcane and rice, O. turbelli sp. n. Beard and Walter, O. ephamnus sp. n. Beard and Walter and O. festucolus sp. n. Beard and Walter from other grasses, are newly described. Previous records of O. grypus in Australia appear to be misidentifications of what is described here as the new species O. zanclopes . 相似文献
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Mohammed Safwat Abdel-Salam Walter Klingmüller 《Molecular & general genetics : MGG》1987,210(1):165-170
Summary A method for transposon mutagenesis in Azospirillum lipoferum 29708 is reported with transposon Tn5. The suicide plasmid pSUP2021 was used to deliver Tn5 in A. lipoferum using Escherichia coli SM10 as the donor. Neomycin-resistant transconjugants were detected at a frequency of 6x10-6 per recipient. Different types of mutants were isolated, e.g. auxotrophic, coloured, IAA-negative, and IAA-overproducers. Among the auxotrophic mutants, cysteine and methionine requirers prevailed. Random Tn5-insertion with only one copy per mutant was demonstrated by Southern blotting and hybridization. Tn5-induced mutants are relatively stable, with reversion rates of 2–20×10-8. A gene which is a part of the carotenoid pathway is closely linked to the histidine genes. The existence of two pathways for IAA production in A. lipoferum is discussed. 相似文献