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201.
Cristine E. A. Carneiro Antonio C. Stabile Frederico P. Gomes Antonio C. S. da Costa Cássia T. B. V. Zaia Dimas A. M. Zaia 《Origins of life and evolution of the biosphere》2017,47(3):323-343
Probably one of the most important roles played by minerals in the origin of life on Earth was to pre-concentrate biomolecules from the prebiotic seas. There are other ways to pre concentrate biomolecules such as wetting/drying cycles and freezing/sublimation. However, adsorption is most important. If the pre-concentration did not occur—because of degradation of the minerals—other roles played by them such as protection against degradation, formation of polymers, or even as primitive cell walls would be seriously compromised. We studied the interaction of two artificial seawaters with kaolinite, bentonite, montmorillonite, goethite, ferrihydrite and quartz. One seawater has a major cation and anion composition similar to that of the oceans of the Earth 4.0 billion years ago (ASW 4.0 Ga). In the other, the major cations and anions are an average of the compositions of the seawaters of today (ASWT). When ASWT, which is rich in Na+ and Cl?, interacted with bentonite and montmorrilonite structural collapse occurred on the 001 plane. However, ASW 4.0 Ga, which is rich in Mg2+ and SO4 2?, did not induce this behavior. When ASW 4.0 Ga was reacted with the minerals for 24 h at room temperature and 80 °C, the release of Si and Al to the fluid was below 1 % of the amount in the minerals—meaning that dissolution of the minerals did not occur. In general, minerals adsorbed Mg2+ and K+ from the ASW 4.0 Ga and these cations could be used for the formation of polymers. Also, when the minerals were mixed with ASW 4.0 Ga at 80 °C and ASWT at room temperature or 80 °C it caused the precipitation of CaSO4?2H2O and halite, respectively. Finally, further experiments (adsorption, formation of polymers, protection of molecules against degradation, primitive cell wall formation) performed under the conditions described in this paper will probably be more representative of what happened on the prebiotic Earth. 相似文献
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Leonardo L. C. Dias Claudete Santa-Catarina Dimas M. Ribeiro Raimundo S. Barros Eny I. S. Floh Wagner C. Otoni 《Plant Cell, Tissue and Organ Culture》2009,99(2):199-208
Levels of ethylene and polyamines (PAs) were measured during organogenesis of hypocotyl explants of two species of passion
fruit (Passiflora cincinnata Masters and Passiflora edulis Sims f. flavicarpa Degener ‘FB-100’) to better understand the relationships of these regulators and their influence on cell differentiation
and morphogenesis. Moreover, histological investigation of shoot ontogenesis was conducted to characterize the different events
involved in cell redifferentiation and regulation of PA and ethylene levels. A delay was observed in morphogenic responses
of P. edulis f. flavicarpa as compared to P. cincinnata, and these changes coincided with production of elevated levels of polyamine and ethylene levels. During differentiation,
cells showed high rates of expansion and elongation, and high ethylene levels were associated with high PA levels, suggesting
that the two biosynthesis pathways were highly regulated. Moreover, their interaction might be an important factor for determining
cell differentiation. The addition of PAs to the culture medium did not promote organogenesis; however, the incorporation
of the PA inhibitor methylglyoxal bisguanylhydrazone in the culture medium reduced shoot bud differentiation, suggesting the
need to maintaining a minimum level of PAs for morphogenic events to take place. 相似文献
204.
Caroline Goujon Rebecca A. Greenbury Stelios Papaioannou Tomas Doyle Michael H. Malim 《Journal of virology》2015,89(8):4676-4680
We have employed molecular genetic approaches to understand the domain organization of the HIV-1 resistance factor myxovirus resistance 2 (MX2). First, we describe an essential triple-arginine motif in the amino-terminal domain. Second, we demonstrate that this 91-residue domain mediates antiviral activity when appended to heterologous proteins, and we provide genetic evidence that protein oligomerization is required for MX2 function. These insights will facilitate future work aiming to elucidate MX2''s mechanism of action. 相似文献
205.
Andersom Milech Einhardt Sandro Ferreira Lillian Mathias Oliveira Dimas Mendes Ribeiro Fabrício Ávila Rodrigues 《Physiologia plantarum》2020,170(4):592-606
Nickel (Ni) and glyphosate (Gl) are able to reduce the symptoms of Asian soybean rust (ASR), caused by Phakopsora pachyrhizi, in soybean. However, their combined effects on the energy balance and ethylene metabolism of soybean plants infected with this fungus has not been elucidated. Therefore, the effects of Ni, Gl, and the combination of Ni + Gl on ASR development, photosynthetic capacity, sugar concentrations, and ethylene concentrations in plants of a Gl-resistant cultivar, uninfected or infected with P. pachyrhizi, were investigated. Inoculated plants supplied with Ni had the highest foliar Ni concentration in all the treatments. Gl had a negative effect on the foliar Ni concentration in Ni-sprayed plants. The ASR severity was reduced in plants sprayed with Ni and Gl. Carotenoid and chlorophyll concentrations were higher in inoculated Ni, Gl, and Ni + Gl plants than in control plants. Based on the chlorophyll a fluorescence parameters, the photosynthetic apparatus of the control inoculated plants was damaged, and the least amount of energy was directed to the photochemistry process in these plants. The reduced capacity of the photosynthetic mechanism to capture light and use the energy absorbed by photosystem II in inoculated plants was reflected in their reduced capacity to process CO2, as indicated by the high internal CO2 concentrations and low rates of net carbon assimilation. The low sugar concentrations in inoculated plants from the control treatment were linked to their reduced photosynthetic capacity due to the high ASR severity. In uninfected plants, the ethylene concentration was not affected by Ni or Gl, while the ethylene concentration decreased in inoculated plants; this decrease was more pronounced in plants from the control treatment than in treated inoculated plants. In conclusion, this study sheds light on the role played by both Ni and Gl in ASR control from a physiological perspective. Soybean plants exposed to Ni and Gl were able to maintain high ethylene concentrations and photosynthetic capacity during the P. pachyrhizi infection process; as a result, these plants consumed less of their reserves than inoculated plants not treated with Ni or Gl. 相似文献