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941.
Georgia Tooulakou Dimosthenis Nikolopoulos Elissavet Dotsika Malvina G. Orkoula Christos G. Kontoyannis Georgios Liakopoulos Maria I. Klapa George Karabourniotis 《Physiologia plantarum》2019,166(3):862-872
The functional role(s) of plant calcium oxalate (CaOx) crystals are still poorly understood. Recently, it was shown that crystals function as dynamic carbon pools whose decomposition could provide CO2 to photosynthesis when stomata are closed (e.g. under drought conditions) and CO2 starvation conditions may be created within the mesophyll. This biochemical process, named as ‘alarm photosynthesis’, can become crucial for plant survival under adverse conditions. Here, we study crystal decomposition under controlled CO2 starvation conditions (either in the shoot or in the root) to obtain a better insight into the process of crystal formation and function. Hydroponically grown pigweed plants were kept in CO2‐free air and/or CO2‐free nutrient medium for 9 days. Crystal volume was monitored daily, and carbon stable isotope composition (δ13C) and Fourier transformation Raman spectra were obtained at the end of the experiment. A considerable reduction in the leaf crystal volume was observed in shoot‐CO2‐starved plants at the end of the experiment. The smallest crystals were isolated from the plants in which carbon was excluded from both the shoot and the root and contained potassium nitrate. Crystal δ13C of CO2‐starved plants was altered in a predicted way. Specifically, it depended on the average calculated isotope fractionation of all carbon fixation processes considered to be contributing in each experimental treatment. The results of the present study confirmed the correlation between CO2 starvation conditions and the CaOx crystal decomposition. Inorganic carbon fixed in the root may represent a major carbon source for CaOx formation. 相似文献
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944.
Acácio S. de Souza Barbara D.C. Pacheco Sergio Pinheiro Estela M.F. Muri Luiza R.S. Dias Camilo H.S. Lima Rafael Garrett Mariana B.M. de Moraes Bruno E.G. de Souza Luciano Puzer 《Bioorganic & medicinal chemistry letters》2019,29(9):1094-1098
Human kallikreins 5 and 7 (KLK5 and KLK7) exhibit trypsin- and chymotrypsin-like activities and are involved in pathologies related to skin desquamation process. A series of new 3-acyltetramic acids were developed as a novel class of inhibitors of KLK5, KLK7 and trypsin enzymes. The nature and length of the acyl chain is crucial to the KLK5, KLK7 and trypsin inhibition activities, and the most potent compounds (but not the most selective) 2b, 2c and 2g showed low micromolar IC50 values. While very few of the compounds were selective for KLK5, the selective inhibition of trypsin against chymotrypsin was achieved. Our molecular modelling studies revealed that the double bond in 2g provided the best fit in the binding site of KLK5, while the hydrogen bonding interactions modulated the best fit of 2c in the binding site of KLK7 due to the hydrophobicity of the cavity. 相似文献
945.
Bacterial L-ASNases (L-asparaginases) catalyse the conversion of L-asparagine into L-aspartate and ammonia, and are widely used for the treatment of ALL (acute lymphoblastic leukaemia). In the present paper, we describe an efficient approach, based on protein chemistry and protein engineering studies, for the construction of trypsin-resistant PEGylated L-ASNase from Erwinia carotovora (EcaL-ASNase). Limited proteolysis of EcaL-ASNase with trypsin was found to be associated with a first cleavage of the peptide bond between Lys53 and Gly54, and then a second cleavage at Arg206-Ser207 of the C-terminal fragment, peptide 54-327, showing that the initial recognition sites for trypsin are Lys53 and Arg206. Site-directed mutagenesis of Arg206 to histidine followed by covalent coupling of mPEG-SNHS [methoxypoly(ethylene glycol) succinate N-hydroxysuccinimide ester] to the mutant enzyme resulted in an improved modified form of EcaL-ASNase that retains 82% of the original catalytic activity, exhibits enhanced resistance to trypsin degradation, and has higher thermal stability compared with the wild-type enzyme. 相似文献
946.
G. Pacheco R. F. Gagliardi L. A. Carneiro C. H. Callado J. F. M. Valls E. Mansur 《Plant Cell, Tissue and Organ Culture》2007,88(2):121-126
Somatic embryogenesis was induced from seed explants of Arachis archeri, A. porphyrocalix (Section Erectoides) and A. appressipila (Section Procumbentes) in response to 6-benzylaminopurine (BAP). Embryo axes first developed into single shoots in response to 4.4 μM BAP. Friable
embryogenic calluses were produced from the hypocotyl region of these explants in response to different BAP concentrations.
Embryonic leaflets also gave rise to friable calluses, but somatic embryos were only observed in explants of A. archeri and A. appressipila. Histological analyses revealed the presence of heart-shaped, torpedo and cotyledonary stages embryos, both as isolated and
fused structures. A low frequency of embryo-to-plant conversion was achieved by inducing shoot development on medium solidified
with 0.5% phytagel and supplemented with 1.5% or 3% sucrose. Rooting was induced on MS supplemented with indole-3-acetic acid
(IAA). 相似文献
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949.
Nassar AF Miyashiro S Oliveira CG Pacheco WA Ogata RA 《Memórias do Instituto Oswaldo Cruz》2007,102(5):639-642
Mycobacterium was verified in animals from a Brazilian dairy herd, a total of 42 samples from 30 cows were submitted to culture and the isolated strains were analyzed by two polymerase chain reaction (PCR), the first specific for species belonging to the Mycobacterium complex (MTBC) and the other for differentiating M. tuberculosis from M. bovis. Twenty seven samples (64.3%) from 18 animals (60%) were positive for mycobacteria by culture, including samples from 15 retrofaryngeal lymphnodes (55.5%), 9 prescapular lymphnodes (33.3%), 2 lungs (7.4%), and 1 liver (3.7%). All isolated colonies were confirmed by PCR to contain MTBC organisms, and were identified as M. bovis by the same methodology. 相似文献
950.
Endophytic streptomycetes have been isolated and characterized from several species of Nothofagus and other plants growing in the southern reaches of Patagonia. No endophytic streptomycete was obtained from any plant species
studied in Northern Patagonia. However, from Southern Patagonia, biologically active Streptomyces spp. from several plant species were isolated. Each isolate, as studied by scanning electron microscopy (SEM), has small
hyphae, some produce typical barrel-shaped spores in culture and each has some unique hyphal surface structures. Interestingly,
although none has any detectable antibacterial killing properties, each has demonstrable killing activity against one or more
pathogenic fungi including representative plant pathogenic organisms such as Phytophthora erythroseptica, Pythium ultimum, Sclerotinia sclerotiorum, Mycosphaerella fijiensis, and Rhizoctonia solani. The 16S rDNA sequences of the isolates were distinct from all other genetic accessions of Streptomyces in GenBank. However, isolate C-2 from Chiliotrichum diffusum (Compositae) is identical, in all respects, to isolate C-4 obtained from Misodendrum punctulatum (Loranthaceae). These results confirm that endophytic streptomycetes represent a novel source of biologically active microorganisms. 相似文献