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121.
Romeu Cardoso Guimarães 《Origins of life and evolution of the biosphere》2011,41(4):357-371
An investigation of the biosynthesis pathways producing glycine and serine was necessary to clarify an apparent inconsistency
between the self-referential model (SRM) for the formation of the genetic code and the model of coevolution of encodings and
of amino acid biosynthesis routes. According to the SRM proposal, glycine was the first amino acid encoded, followed by serine.
The coevolution model does not state precisely which the first encodings were, only presenting a list of about ten early assignments
including the derivation of glycine from serine—this being derived from the glycolysis intermediate glycerate, which reverses
the order proposed by the self-referential model. Our search identified the glycine-serine pathway of syntheses based on one-carbon
sources, involving activities of the glycine decarboxylase complex and its associated serine hydroxymethyltransferase, which
is consistent with the order proposed by the self-referential model and supports its rationale for the origin of the genetic
code: protein synthesis was developed inside an early metabolic system, serving the function of a sink of amino acids; the
first peptides were glycine-rich and fit for the function of building the early ribonucleoproteins; glycine consumption in
proteins drove the fixation of the glycine-serine pathway. 相似文献
122.
Pedro Manuel Sánchez JuradoLuis Romero Rizos María Luisa García-Mauriño GuelbenzuPedro Abizanda Soler 《Revista espa?ola de geriatría y gerontología》2011,46(1):43
A case of primary pulmonary non-Hodgkin's lymphoma is presented. On this occasion, the lymphoma invaded the myocardium, an event which has not previously been reported in the literature. These neoplasms spread by proximity, and invasion of the pericardium, thoracic wall and oesophagus have been described. Our patient died from heart failure. Tumour myocardial infiltration may well have been the determinant cause through various mechanisms, including a decrease in myocardial contractility. Spread into the myocardium may be facilitated by bulky tumour infiltrates in the pleural space. 相似文献
123.
Sérgio L. Morelhão Paulo G. Coelho Marcelo G. Hönnicke 《European biophysics journal : EBJ》2010,39(5):861-865
Optimized experimental conditions for extracting accurate information at subpixel length scales from analyzer-based X-ray
imaging were obtained and applied to investigate bone regeneration by means of synthetic β-TCP grafting materials in a rat
calvaria model. The results showed a 30% growth in the particulate size due to bone ongrowth/ingrowth within the critical
size defect over a 1-month healing period. 相似文献
124.
125.
126.
Cadmium causes the oxidative modification of proteins in pea plants 总被引:23,自引:0,他引:23
M. C. Romero-Puertas J. M. Palma M. Gómez L. A. Del Río & L. M. Sandalio 《Plant, cell & environment》2002,25(5):677-686
In pea (Pisum sativum L.) leaves from plants grown in the presence of 50 µm CdCl2 the oxidative production of carbonyl groups in proteins, the rate of protein degradation and the proteolytic activity were investigated. In leaf extracts the content of carbonyl groups measured by derivatization with 2,4‐dinitrophenylhydrazine (DNPH), was two‐fold higher in plants treated with Cd than in control plants. The identification of oxidized proteins was carried out by sodium dodecyl sulphate‐polyacrylamide gel electrophoresis of proteins derivatized with DNPH and immunochemical detection with an antibody against DNPH. The intensity of the reactive bands was higher in plants exposed to Cd than in controls. By using different antibodies some of the oxidized proteins were identified as Rubisco, glutathione reductase, manganese superoxide dismutase, and catalase. The incubation of leaf crude extracts with increasing H2O2 concentrations showed a progressive enhancement in carbonyl content and the pattern of oxidized proteins was similar to that found in Cd‐treated plants. Oxidized proteins were more efficiently degraded, and the proteolytic activity increased 20% due to the metal treatment. In peroxisomes purified from pea leaves a rise in the carbonyl content similar to that obtained in crude extracts from Cd‐treated plants was observed, but the functionality of the peroxisomal membrane was not apparently affected by Cd. Results obtained demonstrate the participation of both oxidative stress, probably mediated by H2O2, and proteolytic degradation in the mechanism of Cd toxicity in leaves of pea plants, and they appear to be involved in the Cd‐induced senescence previously reported in these plants. 相似文献
127.
128.
JoÃo B. Fernandes Otto R. Gottlieb Lucia M. Xavier 《Biochemical Systematics and Ecology》1978,6(1):55-58
The trunk wood of Aniba riparia (Nees) Mez (Lauraceae) contains flavokawin-B, (2S)-pinostrombin, (2S)-5, 7-di-O-methylpinocembrin, (2R, 3R)-5, 7-di-O-methylpinobanksin, izalpinin and 3,5, 7-tri-O-methylgalangin. Structural comparison of these flavonoids with the pyrones and neolignans, which characterized all previously examined Aniba spp., leads to a chemical classification of the genus. 相似文献
129.
Effects of ethanol and other alkanols on passive proton influx in the yeast Saccharomyces cerevisiae
Ethanol, isopropanol, propanol and butanol enhanced the passive influx of protons into deenergized cells of Saccharomyces cerevisiae. The influx followed first-order kinetics with a rate constant that increased exponentially with the alkanol concentration. The exponential enhancement constants increased with the lipid solubility of the alkanols, which indicated hydrophobic membrane regions as the target sites. While the enhancement constants were independent of pH over the range tested (3.3–5.0), the rate constants decreased linearly with increasing extracellular proton concentration, indicating the presence of an additional surface barrier against proton penetration, the effectiveness of which increased with protonation. The alkanols affected the acidification curves of energized yeast suspensions in such a way that the final pH values were linear functions of the alkanol concentrations. These results were consistent with a balance between active and passive proton movements at the final pH, the exponential enhancement constants calculated from the slopes being nearly identical with those obtained with deenergized cells. It was concluded that passive proton influx contributes to the kinetics of acidification in S. cerevisiae and that uncoupling contributes to the overall kinetics of alkanol-inhibited secondary active transport across the yeast plasma membrane. 相似文献
130.