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1.
The Phorusrhacidae, a group of large terrestrial carnivorous birds mostly known from the Cenozoic of South America, are often placed in a superfamily, for which the taxon name Phororhacoidea Patterson, 1941 is frequently used. However, according to the International Code of Zoological Nomenclature, Phororhacoidea is not valid. The proper taxon name at the superfamily level is Phorusrhacoidea Ameghino, 1889. 相似文献
2.
The effects of FeCl 3 and Fe–EDTA on the development of psoriasis were studied in the mouse model of vaginal epithelium and tail epidermis. The
mitoses of vaginal epithelial cell in female mice of their estrogenic stage and the formation of granular cell layers in male
mouse tail scale were observed. Mice were randomly divided into eight groups and treated with normal saline, methotrexate,
and different doses of two iron forms, FeCl 3 and Fe–EDTA, respectively, for 10 days. To explore the influence of FeCl 3 and Fe–EDTA on the excretion of Cu, Fe, Zn, Ca, Mg, Mn, and Se, the concentration of those elements in liver and kidney was
analyzed by atomic absorption spectrometry. The different doses of FeCl 3 or Fe–EDTA could obviously inhibit the mitoses of vaginal epithelial cell ( p< 0.05) and promote the formation of granular cell layers in mice tail scale ( p < 0.05). No statistically significant results were found between the groups of FeCl 3 and Fe–EDTA, and between experimental groups and methotrexate group acted as the positive control ( p>0.05). Compared with the negative group, the concentrations of Cu, Fe, Zn, Ca, Mg, Mn, and Se in liver and kidney of experimental
groups and positive control group were not significantly changed ( p > 0.05). FeCl 3 and Fe–EDTA are as effective as methotrexate on inhibiting hyperplasia of epidermal cells and increasing the formation of
granular cell layers, and the concentrations of Cu, Fe, Zn, Ca, Mg, Mn, and Se in liver and kidney of experimental groups
and positive control group were not significantly changed compared with the negative group, possibly retarding the development
of psoriasis. 相似文献
3.
Lead (Pb) is a trace metal element in the human body. In order to understand the hazard mechanism of the elevated blood lead
level on the human body, the effect of Pb 2+ on the human ether-à-go-go-related gene (hERG) K + channel in the HEK 293 cell was investigated for the first time using whole-cell patch clamp technique, molecular dynamics
simulation, and quantum chemistry calculation methods. We found that Pb 2+ obviously inhibits the current of the hERG K + channel, and delays the “activation” and “deactivation” of the hERG K + channel, indicating that Pb 2+ evidently decreases the function of the K + channel in the cell. The effect is increased with increasing the concentration of Pb 2+. When the concentration of Pb 2+ is 400 μg L −1, the function of the K + channel is entirely lost. The results from the molecular dynamics simulation and quantum chemistry calculation indicated
that Pb 2+ can coordinate with the oxygen/sulfur atoms in the K + channel protein, leading to the decrease in the function of the K + channel. According to the experimental results, we suggested that once the K + channel in the human body was irreversibly inactivated by Pb 2+, it would affect the treatment and prognosis of Pb 2+ intoxication. 相似文献
4.
The activity of dehydroleucodine, a sesquiterpene lactone obtained from Artemisia douglasiana, was studied in mice small intestinal
transit. Its mechanism was evaluated in the presence of several adrenergic and cholinergic antagonist drugs and one opioid
antagonist. Docking of dehydroleucodine into the homology model of the α2-adrenergic receptor allowed us to analyze the structural
basis of their interactions. The experiments showed that dehydroleucodine delayed intestinal transit. The docking of dehydroleucodine
showed a unique binding site, equivalent to the binding site of carozolol in the β-adrenergic receptor. The results suggested
that dehydroleucodine produced an inhibitory effect on intestinal transit. Its action could be mediated, at least in part,
through the α2-adrenergic receptor. 相似文献
6.
Summary Molecular mechanisms of thermoinactivation of the thermostable -amylase of Bacillus caldovelox were examined. Monomolecular conformational processes were found to be the major causes of thermoinactivation at both pH 4.5 and 8.0. The enzyme possessed considerable additional thermostability at pH 8.0, with half-lives of 0.75 and 7.0 min at 90° C and pH 4.5 and 8.0, respectively. The amino acid composition was examined with respect to the underlying thermostability exhibited by this enzyme. The inherent thermostability exhibited may be due to the high proline content (4.47 mol%), but more likely due to the high content of residues forming hydrophobic bonds (60.89 mol%) allied to a low content of residues responsible for ionic interactions (28.34 mol%).
Offprint requests to: C. T. Kelly 相似文献
7.
The effect of the concentration of an inducer (IPTG) and the time of induction at 37°С on the heterologous synthesis of the mature membrane protein phospholipase А 1 (PldA) from Yersinia pseudotuberculosis in the form of inclusion bodies (IBs) and on the physicochemical and structural characteristics of IBs has been studied. The sizes, shape, stability (solubility in urea and detergents, resistance against proteolysis), the secondary structure of the protein of IBs, and the presence of amyloid structures have been determined by electron microscopy, dynamic light scattering, and optical spectroscopy. It was found that IBs have a shape close to spherical and a rough surface and are cleaved by proteinase K. The protein contained in IBs has an ordered secondary structure with a high content of β-structure. As the inducer concentration and the time of expression increase, the conformation of the recombinant protein in IBs undergoes changes, as indicated by an increase in the stability of IBs and a decrease in the enzymatic activity of the protein. When IBs are dissolved in 0.06% SDS and 5 M urea, the recombinant protein retains the secondary structure in a partially modified form, and the addition of a zwitterionic detergent at a micellar concentration does not transform the protein conformation into the native one. 相似文献
9.
Effect of nanoparticles of different nature on development of the populations of top and bottom fermentation brewers’ yeasts ( Saccharomyces cerevisiae) on various media and on ethanol accumulation during wort fermentation was studied. In some cases the presence of nanoparticles in the medium was shown to affect the monitored parameters, primarily the yeast cell titer. Direction and intensity of this effect depend on a number of factors: nanopreparation kind and concentration, medium composition, and cultivation conditions. Inhibition of development of yeast populations was most pronounced in the presence of the silver nanopreparation, while zinc nanoparticles and zinc oxide nanopreparation had the least effect. At the same time, specific concentrations of some nanoparticles stimulated growth of the population and yeast metabolism. 相似文献
10.
Summary. Glutamate increases the extracellular adenosine levels, an important endogenous neuromodulator. The neurotoxicity induced
by glutamate increases the ecto-5′-nucleotidase activity in neurons, which produces adenosine from AMP. L- and D-aspartate
(Asp) mimic most of the actions of glutamate in the N-methyl-D-aspartate (NMDA) receptors. In the present study, both amino
acids stimulated the ecto-5′-nucleotidase activity in cerebellar granule cells. MK-801 and AP-5 prevented the L- and D-Asp-evoked
activation of ecto-5′-nucleotidase. Both NMDA receptor antagonists prevented completely the damage induced by L-Asp, but partially
the D-Asp-induced damage. The antagonist of adenosine A 2A receptors (ZM 241385) prevented totally the L- Asp-induced cellular death, but partially the neurotoxicity induced by D-Asp
and the antagonist of adenosine A 1 receptors (CPT) had no effect. The results indicated a different involvement of NMDA receptors on the L- or D-Asp-evoked
activation of ecto-5′-nucleotidase and on cellular damage. The adenosine formed from ecto-5′-nucleotidase stimulation preferentially
acted on adenosine A 2A receptor which is probably co-operating with the neurotoxicity induced by amino acids. 相似文献
11.
Enzyme engineering was performed to link the β-glucosidase enzyme (BGL1) from Saccharomycopsis fibuligera to the cellulose-binding domain (CBD2) of Trichoderma reesei cellobiohydrolase (CBHII) to investigate the effect of a fungal CBD on the enzymatic characteristics of this non-cellulolytic
yeast enzyme. Recombinant enzymes were constructed with single and double copies of CBD2 fused at the N-terminus of BGL1 to
mimic the two-domain organization displayed by cellulolytic enzymes in nature. The engineered S. fibuligera β-glucosidases were expressed in Saccharomyces cerevisiae under the control of phosphoglycerate-kinase-1 promoter ( PGK1
P
) and terminator ( PGK1
T
) and yeast mating pheromone α-factor secretion signal ( MFα1
S
). The secreted enzymes were purified and characterized using a range of cellulosic and non-cellulosic substrates to illustrate
the effect of the CBD on their enzymatic activity. The results indicated that the recombinant enzymes of BGL1 displayed a
2–4-fold increase in their hydrolytic activity toward cellulosic substrates like avicel, amorphous cellulose, bacterial microcrystalline
cellulose, and carboxy methyl cellulose in comparison with the native enzyme. The organization of the CBD in these recombinant
enzymes also resulted in enhanced substrate affinity, molecular flexibility and synergistic activity, thereby improving the
ability of the enzymes to act on and hydrolyze cellulosic substrates, as characterized by adsorption, kinetics, thermal stability,
and scanning electron microscopic analyses. 相似文献
12.
Even though the incidence of pregnancies in the female recipients is lower and also chronic renal disease in male patients is associated with impaired spermatogenesis, the health of the children born to these patients was not studied. In this report, we discuss information on the growth and development of offspring of 248 male and female kidney recipient patients. Physical and routine clinical measurements of the 252 offspring (129 male and 123 female) born to these transplantation patients were made along with the intelligence tests. In some of these children chest X-ray and immune indices were assessed. Among the recipients, 219 males fathered 223 children with an average birth weight of 3,255 ± 374 g and 29 female recipients gave birth to 29 children with an average birth weight of 2,923 ± 551. While most of these children were normal, we noticed a case of soft double toe, a case of short tongue tie, five cases of marginal mental retardation, three cases of proteinuria, six cases of microscopic hematuria, 15 cases of low hemoglobin, and 21 cases with recurrent respiratory tract infections. We conclude that kidney transplantation has no significant impact on the growth, development, health, and intelligence of the offspring born to recipients. 相似文献
16.
The dependence of the 13C chemical shift on side-chain orientation was investigated at the density functional level for a two-strand antiparallel
β-sheet model peptide represented by the amino acid sequence Ac-(Ala) 3-X-(Ala) 12-NH 2 where X represents any of the 17 naturally occurring amino acids, i.e., not including alanine, glycine and proline. The dihedral
angles adopted for the backbone were taken from, and fixed at, observed experimental values of an antiparallel β-sheet. We
carried out a cluster analysis of the ensembles of conformations generated by considering the side-chain dihedral angles for
each residue X as variables, and use them to compute the 13C chemical shifts at the density functional theory level. It is shown that the adoption of the locally-dense basis set approach for the quantum chemical calculations enabled us to reduce the length of the chemical-shift calculations
while maintaining good accuracy of the results. For the 17 naturally occurring amino acids in an antiparallel β-sheet, there
is (i) good agreement between computed and observed 13C α and 13C β chemical shifts, with correlation coefficients of 0.95 and 0.99, respectively; (ii) significant variability of the computed
13C α and 13C β chemical shifts as a function of χ 1 for all amino acid residues except Ser; and (iii) a smaller, although significant, dependence of the computed 13C α chemical shifts on χ ξ (with ξ ≥ 2) compared to χ 1 for eleven out of seventeen residues. Our results suggest that predicted 13C α and 13C β chemical shifts, based only on backbone (φ,ψ) dihedral angles from high-resolution X-ray structure data or from NMR-derived
models, may differ significantly from those observed in solution if the dihedral-angle preferences for the side chains are
not taken into account.
Electronic supplementary material Supplementary material is available in the online version of this article at and is accessible for authorized users. 相似文献
17.
Leptospira infection involves the adhesion of the bacteria followed by invasion of the host crossing the extracellular matrix barrier.
In an effort to understand the molecular mechanism of this process, the possibility of occurrence of matrix degrading enzymes
from Leptospira was investigated. Zymographic analysis showed that the outer membrane of Leptospires contains a gelatinase of average molecular
size of 46 kDa. The gelatinase exhibited maximum activity at neutral pH and was inhibited by metal chelators such as EGTA,
EDTA, and Orthophenanthroline and was activated by calcium, magnesium, zinc, and copper, suggesting that it is a membrane-associated neutral matrix metalloproteinase.
Analysis of the production of the enzyme by various serovars showed that the pathogenic serovars expressed significant amount
of this enzyme while nonpathogenic forms either did not express or showed only very low activity, suggesting that this enzyme
may be associated with pathogenesis of leptospirosis. 相似文献
18.
Catalase–peroxidases (KatGs) have two peroxidase-like domains. The N-terminal domain contains the heme-dependent, bifunctional active site. Though the C-terminal domain lacks the ability to bind heme or directly catalyze any reaction, it has been proposed to serve as a platform to direct the folding of the N-terminal domain. Toward such a purpose, its I′-helix is highly conserved and appears at the interface between the two domains. Single and multiple substitution variants targeting highly conserved residues of the I′-helix were generated for intact KatG as well as the stand-alone C-terminal domain (KatG C). Single variants of intact KatG produced only subtle variations in spectroscopic and catalytic properties of the enzyme. However, the double and quadruple variants showed substantial increases in hexa-coordinate low-spin heme and diminished enzyme activity, similar to that observed for the N-terminal domain on its own (KatG N). The analogous variants of KatG C showed a much more profound loss of function as evaluated by their ability to return KatG N to its active conformation. All of the single variants showed a substantial decrease in the rate and extent of KatG N reactivation, but with two substitutions, KatG C completely lost its capacity for the reactivation of KatG N. These results suggest that the I′-helix is central to direct structural adjustments in the adjacent N-terminal domain and supports the hypothesis that the C-terminal domain serves as a platform to direct N-terminal domain conformation and bifunctionality. 相似文献
19.
The effect of contrast medium SonoVue® on the electric charge density of blood cells (erythrocytes and thrombocytes) was measured using a microelectrophoretic method. We examined the effect of adsorbed H + and OH ? ions on the surface charge of erythrocytes or thrombocytes. Surface charge density values were determined from electrophoretic mobility measurements of blood cells performed at various pH levels. The interaction between solution ions and the erythrocyte’s or thrombocyte’s surface was described by a four-component equilibrium model. The agreement between the experimental and theoretical charge variation curves of the erythrocytes and thrombocytes was good at pH 2–9. The deviation observed at a higher pH may be caused by disregarding interactions between the functional groups of blood cells. 相似文献
20.
Our study focuses on the study of the phosphorus efficiency on the mineral nutrition of a leguminous plant; to study this efficiency, we tested the effect of increasing doses of phosphorus on the mineral nutrition of faba bean and on the concentration of Nt (total nitrogen), Pi (available phosphorus), KE (exchangeable potassium), C (organic carbon), and the organic matter (OM) rate in the rhizospheric soil after harvest, as well as the concentration of N, P, K, Na, and Ca in the roots, stems, leaves, and seeds of faba bean. The faba bean crop was subjected to four phosphorus doses (P0?=?0 kg/ha; P1?=?70 kg/ha; P2?=?140 kg/ha; P3?=?210 kg/ha). The main results obtained showed that the concentration of the mineral elements in the different faba bean parts reacted differently to the phosphorus treatments. Regarding the dosage of nutrients in the different parts of the faba bean, the results obtained highlight that Pi deficiency in the soil does not only affect phosphate nutrition but can also affect the absorption of other mineral elements, a synergy is recorded between the K concentration in the roots and in the stems with the organic carbon in the soil, and an antagonism between K and Na in the different parts of the plant. All the results obtained in this work show that a phosphate fertilization for doses between 70 kg/ha and 140 kg/ha of P2O5 improves the microbial life of soil microorganisms. 相似文献
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