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31.
Kleber Queiroz FerreiraAngélica Maria Lucchesi Zênis Novais da RochaRoberto Santana da Silva 《Inorganica chimica acta》2002,328(1):147-151
We report here the synthesis, characterization and kinetic studies of cis-[RuCl2(cyclen)]+ in aqueous solution, where cyclen is the macrocyclic ligand 1,4,7,10-tetraazacyclododecane. The complex releases one Cl− producing cis-[RuCl(OH)(cyclen)]+ in aqueous solution at pH 4.60. The product of this reaction was characterized by Ultraviolet-Visible (UV-Vis) spectrum in comparison to the synthesized cis-[RuCl(OH)(cyclen)](BF4)·2H2O. The electrochemical data showed that Epc of the Ru(III/II) peak increases as the macrocycle ring size decreases and also when the trans conformation is changed to cis. The chloride affinity of Ru(III) depends on the macrocycle ring size since cis-[RuCl2(cyclam)]+ (cyclam=1,4,8,11-tetraazacyclotetradecane) does not release chloride for at least 12 h. The overall effect between cyclam and cyclen reflects the fact that the electron involved in the reduction enters a nonbonding π-d orbital and its energy is affected by the macrocyclic ligand. 相似文献
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Synthetic Lethality and Semi-Lethality among Functionally Related Mutants of DROSOPHILA MELANOGASTER 总被引:2,自引:2,他引:0
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John C. Lucchesi 《Genetics》1968,59(1):37-44
34.
Triploid intersexes homozygous for a mutant (msl-2) known to impede the hyperactivation of the X chromosome in diploid males differentiate into adults, sexually indistinguishable from their heterozygous sibs. A shift toward female sexual differentiation mediated by manipulating the rearing temperature is accompanied by an apparent increase in the level of an X-linked gene product. This unexpected result is rationalized in terms of differential lethality of individuals at the two extremities of the distribution of X-activity levels in intersexes raised at a particular temperature. No evidence of a mosaicism comparable to the sexual mosaicism exhibited could be found with respect to an X-linked gene product in triploid intersexes. 相似文献
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The increase of cholinesterase (ChE), acid phosphatase (Ac.Pase), and phospholipase C (PLC) activities byPseudomonas aeruginosa was associated with the choline consumption in growth media of varied composition (high or low Pi concentrations, presence or absence of ammonium ion, amino acids, polyamines, peptone, or tricarboxylic acid cycle intermediates). The highest production of the three enzymes occurred in the late stationary growth phase. The simultaneous presence of alkaline phosphatase (Alk.Pase) and the above enzymes was noted when the bacteria were grown in low Pi medium plus choline, in the absence of a preferred carbon source. The importance of choline in the production of ChE, Ac.Pase, and PLC was observed in either clinical isolates or collection strains ofP. aeruginosa. These enzymes catalyze the hydrolysis of acetylcholine, phosphorylcholine, and phosphatidylcholine. Through their action the bacteria may break down various compounds (e.g., acetylcholine, from the corneal epithelium; lung surfactant dipalmitoylphosphatidylcholine; phosphorylcholine, a product of the PLC action) or cell membranes through the coordinated action of PLC and Ac.Pase or Alk.Pase. The final consequence of the action of these enzymes is an increase of the free choline concentration. Extrapolated to an in vivo situation, if the stationary growth phase resembles the conditions thatP. aeruginosa encounters in its natural environments, then it is possible to include choline among the factors promoting the pathogenicity of this bacterium. 相似文献
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The main features of an interstitial ciliate community, living in the coastal sand of the Mediterranean sea, were analyzed during a one-year survey, carried out on 113 samples. The community was composed of 56 species, 31 of which belong to 8 resident genera. Total density varied from 0 to 410 individuals cm–3 and followed a Spring-Summer and an Autumn-Winter trend, not related to temperature or to any single abiotic variable (interstitial dissolved O2, grain sand size, salinity), although the density of some taxa was related to one abiotic factor. During Spring, diversity increased by a synchronous bloom involving the whole community. Some taxa, such as the predator Lacrymaria and its prey Frontonia, were significantly associated. The finding of the simultaneous bloom of congeneric species, like that of the genus Remanella suggests that they respond to the same environmental factors, and avoid interspecific competition. 相似文献
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Gloria I. Lucchesi Teresita A. Lisa Cesar H. Casale Carlos E. Domenech 《Current microbiology》1995,30(1):55-60
The present study demonstrates that under conditions of iso or hyperosmolarity, P. aeruginosa utilized carnitine as the carbon, nitrogen or carbon and nitrogen sources. As occurred in the case of choline, the bacteria synthesized cholinesterase (ChE), acid phosphatase (Ac.Pase) and phospholipase C (PLC) under any of these conditions and in the presence of high or low Pi concentrations.Carnitine acted as an osmoprotectant when the cells were grown in the presence of preferred carbon and nitrogen sources and high NaCl concentrations. Under these conditions the three enzyme activities were not produced.The osmotically stressed bacteria grown under any of the above conditions accumulated betaine. Its presence indicated that carnitine may be metabolized by P. aeruginosa to produce betaine which could account for the induction of the three enzyme activities or its action as an osmoprotectant.The phosphatidylcholine encountered in the host cell membranes allows the bacteria to obtain free choline by the coordinated action of PLC and Ac.Pase. Since the consequence of this action may be cell disruption, the increase of free carnitine in the natural environment of the bacteria is also possible. These two compounds, choline and carnitine, acting in conjunction or separately, may increase the production of PLC and Ac.Pase activities by P. aeruginosa and thus enhance the degradative effect upon the host cells. 相似文献