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991.
Microalgae are regarded as a potential biomass source for biofuel purposes. With regard to bioethanol production, microalgae seem to overcome traditional substrate drawbacks. Enzymatic activities are responsible for carbon allocation and hence for carbohydrate profiles. Enzyme activities may be manipulated by metabolic engineering; however, this goal may also be achieved by controlling environmental conditions of the culture system. We outline the key-enzymes as well as the main operational conditions applied to microalgae growth (inorganic nutrient supplementation, irradiance and temperature) that affect carbohydrate synthesis on microalgae and cyanobacteria. Normally, harsh conditions are needed for such a goal and thus, arrested microalgae growth may occur. Potential strategies to avoid arrested growth, while enhancing carbohydrate accumulation, were also pointed out in this review. 相似文献
992.
Takeshi Nishimura Kiminori Toyooka Mayuko Sato Sachiko Matsumoto M. Mercedes Lucas Miroslav Strnad Franti?ek Balu?ka Tomokazu Koshiba 《Plant signaling & behavior》2011,6(12):2013-2022
To investigate the distribution of IAA (indole-3-acetic acid) and the IAA synthetic cells in maize coleoptiles, we established immunohistochemistry of IAA using an anti-IAA-C-monoclonal antibody. We first confirmed the specificity of the antibody by comparing the amounts of endogenous free and conjugated IAA to the IAA signal obtained from the IAA antibody. Depletion of endogenous IAA showed a corresponding decrease in immuno-signal intensity and negligible cross-reactivity against IAA-related compounds, including tryptophan, indole-3-acetamide, and conjugated-IAA was observed. Immunolocalization showed that the IAA signal was intense in the approximately 1 mm region and the outer epidermis at the approximately 0.5 mm region from the top of coleoptiles treated with 1-N-naphthylphthalamic acid. By contrast, the IAA immuno-signal in the outer epidermis almost disappeared after 5-methyl-tryptophan treatment. Immunogold labeling of IAA with an anti-IAA-N-polyclonal antibody in the outer-epidermal cells showed cytoplasmic localization of free-IAA, but none in cell walls or vacuoles. These findings indicated that IAA is synthesized in the 0–2.0 mm region of maize coleoptile tips from Trp, in which the outer-epidermal cells of the 0.5 mm tip are the most active IAA synthetic cells. 相似文献
993.
Felix Liechti Janine Aschwanden Jan Blew Mathieu Boos Robin Brabant Adriaan M. Dokter Vladislav Kosarev Maryna Lukach Mercedes Maruri Maarten Reyniers Inbal Schekler Heiko Schmaljohann Baptiste Schmid Nadja Weisshaupt Nir Sapir 《Ecography》2019,42(5):887-898
Large parts of the continents are continuously scanned by terrestrial weather radars to monitor precipitation and wind conditions. These systems also monitor the mass movements of bird, bat, and insect migration, but it is still unknown how many of these systems perform with regard to detection and quantification of migration intensities of the different groups. In this study that was undertaken within five regions across Europe and the Middle East we examined to what extent bird migration intensities derived from different weather radars are comparable between each other and relate to intensities measured by local small‐scaled radars, some of them specifically developed to monitor birds. Good correspondence was found for the relative day‐to‐day pattern in migration intensities among most radar systems that were compared. Absolute intensities varied between different systems and regions. The findings of this study can be used to infer about absolute bird migration intensities measured by different radar systems and consequently help resolving methodological issues regarding the estimation of migrant numbers in the Western‐Palearctic region. It further depicts a scientific basis for the future monitoring of migratory bird populations across a large spatio‐temporal scale, predicting their movements and studying its consequences on ecological systems and human lives. 相似文献
994.
The nitrate reductase activity from Chlamydomonas reinhardtii was not altered when extracts were incubated with yeast 14-3-3 proteins in the presence of Mg-ATP. However, the C. reinhardtii extracts contained 14-3-3 proteins capable of inhibiting the spinach nitrate reductase, raising the question of their physiological
substrates. Two C. reinhardtii proteins of about 48 and 35 kDa were eluted from 14-3-3 affinity chromatography columns and bound to 14-3-3s in overlay assays.
The 48-kDa protein corresponded to the cytosolic isoform of glutamine synthetase (GS1). The GS1 was phosphorylated by a Ca2+- and calmodulin-dependent protein kinase partially purified from the alga. However, neither phosphorylation nor 14-3-3 binding
seemed to change GS catalytic activity.
Received: 3 February 2000 / Accepted: 6 May 2000 相似文献
995.
Mercedes Wrischer 《Protoplasma》1978,97(1):85-92
Summary Photooxidation of diaminobenzidine (DAB) has been used to detect ultrastructurally the photosynthetic activity (photosystem I) in the thylakoids of etiochloroplasts in greening bean leaves. The result of this photooxidation is a dark (osmiophilic) deposit which accumulates at first in certain portions of the primary thylakoids. In the course of further greening this area enlarges more and more and at last all the thylakoids become uniformly dark. It has been shown that the beginning of the appearance of the DAB deposits and the speed of their accumulation in the thylakoids largely depends on the experimental conditions of the plants: in leaves maintained in damp atmosphere the first DAB deposits appear between the first and the second hour of greening, while in those kept in dry air this does not happen until three or more hours in light.The tubules of the transformed prolamellar bodies in etiochloroplast—at least at the beginning of their dispersion — do not react with DAB. The tubules formedde novo after a period of darkness in young chloroplasts remain also without DAB deposits. 相似文献
996.
Analia I. Romero José M. Bermudez Mercedes Villegas María F. Dib Ashur Mónica L. Parentis Elio E. Gonzo 《AAPS PharmSciTech》2016,17(4):898-906
Poly(3-hydroxybutyrate) (PHB) biodegradable polymeric membranes were evaluated as platform for progesterone (Prg)-controlled release. In the design of new drug delivery systems, it is important to understand the mass transport mechanism involved, as well as predict the process kinetics. Drug release experiments were conducted and the experimental results were evaluated using engineering approaches that were extrapolated to the pharmaceutical field by our research group. Membranes were loaded with different Prg concentrations and characterized by scanning electron microscopy (SEM), differential scanning calorimetry (DSC), and Fourier transform infrared spectroscopy (FTIR). SEM images showed that membranes have a dense structure before and after the progesterone addition. DSC and FTIR allowed determining the influence of the therapeutic agent in the membrane properties. The in vitro experiments were performed using two different techniques: (A) returning the sample to the receptor solution (constant volume of the delivery medium) and (B) extracting total volume of the receptor solution. In this work, we present a simple and accurate “lumped” second-order kinetic model. This lumped model considers the different mass transport steps involved in drug release systems. The model fits very well the experimental data using any of the two experimental procedures, in the range 0?≤?t?≤?∞ or 0?≤?M t ?≤?M ∞. The drug release analysis using our proposed approaches is relevant for establishing in vitro–in vivo correlations in future tests in animals. 相似文献
997.
998.
999.
Fluxes of nitrogen and phosphorus in a gallery forest in the Cerrado of central Brazil 总被引:1,自引:0,他引:1
Lucilia Maria Parron Mercedes Maria Cunha Bustamante Daniel Markewitz 《Biogeochemistry》2011,105(1-3):89-104
The Gallery forests of the Cerrado biome play a critical role in controlling stream chemistry but little information about biogeochemical processes in these ecosystems is available. This work describes the fluxes of N and P in solutions along a topographic gradient in a gallery forest. Three distinct floristic communities were identified along the gradient: a wet community nearest the stream, an upland dry community adjacent to the woodland savanna and an intermediate community between the two. Transects were marked in the three communities for sampling. Fluxes of N from bulk precipitation to these forests resulted in deposition of 12.6 kg ha?1 y?1 of total N of which 8.8 kg ha?1 was as inorganic N. The throughfall flux of total N was generally <8.4 kg ha?1 year?1. Throughfall NO3?CN fluxes were higher (7?C32%) while NH4?CN and organic N fluxes were lower (54?C69% and 5?C46%) than those in bulk precipitation. The throughfall flux was slightly lower for the wet forest community compared to other communities. Litter leachate fluxes differed among floristic communities with higher NH4?CN in the wet community. The total N flux was greater in the wet forest than in the dry forest (13.5 vs. 9.4 kg ha?1 year?1, respectively). The stream water had total N flux of 0.3 kg ha?1 year?1. The flux of total P through bulk precipitation was 0.7 kg ha?1 year?1 while the mean fluxes of total P in throughfall (0.6 kg ha?1 year?1) and litter leachate (0.5 kg ha?1 year?1) declined but did not differ between communities. The low concentrations presented in soil solution and low fluxes in stream water (0.3 and 0.1 kg ha?1 year?1 for N and P, respectively) relative to other flowpaths emphasize the conservative nutrient cycling of these forests and the importance of internal recycling processes for the maintenance and conservation of riparian and stream ecosystems in the Cerrado. 相似文献
1000.
Mercedes Esparza-Perusquía Sofía Olvera-Sánchez Oscar Flores-Herrera Héctor Flores-Herrera Alberto Guevara-Flores Juan Pablo Pardo María Teresa Espinosa-García Federico Martínez 《Biochimica et Biophysica Acta (BBA)/General Subjects》2015