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排序方式: 共有256条查询结果,搜索用时 15 毫秒
21.
Dynamic alteration of soluble serum biomarkers in healthy aging 总被引:2,自引:1,他引:1
Dysbalanced production of inflammatory cytokines is involved in immunosenescence in aging. The age-related changes of the levels of circulating inflammatory mediators and their clinical importance have not been investigated until recently. Still, little is known about the influence of aging on circulating levels of many cytokines, chemokines, growth factors, and angiogenic factors. In the present study, we evaluated the effect of aging on 30 different serum biomarkers involved in pro- and anti-inflammatory responses using multianalyte LabMAP Luminex technology. The simultaneous measurement of serological markers has been done in 397 healthy subjects between 40 and 80 years old. We demonstrated an increase in serum interferon-gamma-inducible chemokines (MIG and IP-10), eotaxin, chemoattractant for eosinophils, and soluble TNFR-II with advancing age. Serum levels of EGFR and EGF, important regulators of cell growth and differentiation, were decreased with age in healthy donors. These data suggest novel pathways, which may be involved in age-associated immunosenescence. 相似文献
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Alvarez-Venegas R Sadder M Tikhonov A Avramova Z 《Molecular biology and evolution》2007,24(2):482-497
The presence of Supressor of variegation-Enhanser of zeste-Trithorax (SET) domain genes in bacteria is a current paradigm for lateral genetic exchange between eukaryotes and prokaryotes. Because a major function of SET domain proteins is the chemical modification of chromatin and bacteria do not have chromatin, there is no apparent functional requirement for the existence of bacterial SET domain genes. Consequently, their finding in only a small fraction of pathogenic and symbiotic bacteria was taken as evidence that bacteria have obtained the SET domain genes from their hosts. Furthermore, it was proposed that the products of the genes would, most likely, be involved in bacteria-host interactions. The broadened scope of sequenced bacterial genomes to include also free-living and environmental species provided a larger sample to analyze the bacterial SET domain genes. By phylogenetic analysis, examination of individual chromosomal regions for signs of insertion, and evaluating the chromosomal versus SET domain genes' GC contents, we provide evidence that SET domain genes have existed in the bacterial domain of life independently of eukaryotes. The bacterial genes have undergone an evolution of their own unconnected to the evolution of the eukaryotic SET domain genes. Initial finding of SET domain genes in predominantly pathogenic and symbiotic bacteria resulted, most probably, from a biased sample. However, a lateral transfer of SET domain genes may have occurred between some bacteria and a family of Archaea. A model for the evolution and distribution of SET domain genes in bacteria is proposed. 相似文献
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Yakovlev Andrei Novoderezhkin Vladimir Taisova Alexandra Shuvalov Vladimir Fetisova Zoya 《Photosynthesis research》2015,125(1-2):31-42
Photosynthesis Research - Isotropic and anisotropic pump-probe spectra of Cfx. aurantiacus chlorosomes were measured on the fs-through ps-time scales for the B798 BChl a Q y band upon direct... 相似文献
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Using atomic force microscopy (AFM) we investigated the interaction of amyloid beta (Aβ) (1–42) peptide with chemically modified surfaces in order to better understand the mechanism of amyloid toxicity, which involves interaction of amyloid with cell membrane surfaces. We compared the structure and density of Aβ fibrils on positively and negatively charged as well as hydrophobic chemically-modified surfaces at physiologically relevant conditions. We report that due to the complex distribution of charge and hydrophobicity amyloid oligomers bind to all types of surfaces investigated (CH3, COOH, and NH2) although the charge and hydrophobicity of surfaces affected the structure and size of amyloid deposits as well as surface coverage. Hydrophobic surfaces promote formation of spherical amorphous clusters, while charged surfaces promote protofibril formation. We used the nonlinear Poisson-Boltzmann equation (PBE) approach to analyze the electrostatic interactions of amyloid monomers and oligomers with modified surfaces to complement our AFM data. 相似文献
27.
Penicillin amidase (PA) is a bacterial periplasmic enzyme synthesized as a pre-pro-PA precursor. The pre-sequence mediates membrane translocation. The intramolecular pro-sequence is expressed along with the A and B chains but is rapidly removed in an autocatalytic manner. In extensive studies we show here that the pro-peptide is required for the correct folding of PA. Pro-PA and PA unfold via a biphasic transition that is more pronounced in the case of PA. According to size-exclusion chromatography and limited proteolysis experiments, the inflection observed in the equilibrium unfolding curves corresponds to an intermediate in which the N-terminal domain (A-chain) still possesses native-like topology, whereas the B-chain is unfolded to a large extent. In a series of in vitro experiments with a slow processing mutant pro-PA, we show that the pro-sequence in cis functions as a folding catalyst and accelerates the folding rate by seven orders of magnitude. In the absence of the pro-domain the PA refolds to a stable inactive molten globule intermediate that has native-like secondary but little tertiary structure. The pro-sequence of the homologous Alcaligenes faecalis PA can facilitate the folding of the hydrolase domain of Escherichia coli PA when added in trans (as a separate polypeptide chain). The isolated pro-sequence has a random structure in solution. However, difference circular dichroism spectra of native PA and native PA with pro-peptide added in trans suggest that the pro-sequence adopts an alpha-helical conformation in the context of the mature PA molecule. Furthermore, our results establish that Ca2+, found in the crystal structure, is not directly involved in the folding process. The cation shifts the equilibrium towards the native state and facilitates the autocatalytic processing of the pro-peptide. 相似文献
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Siderophore uptake in bacteria and the battle for iron with the host; a bird’s eye view 总被引:1,自引:0,他引:1
Byron C. Chu Alicia Garcia-Herrero Ted H. Johanson Karla D. Krewulak Cheryl K. Lau R. Sean Peacock Zoya Slavinskaya Hans J. Vogel 《Biometals》2010,23(4):601-611
Siderophores are biosynthetically produced and secreted by many bacteria, yeasts, fungi and plants, to scavenge for ferric
iron (Fe3+). They are selective iron-chelators that have an extremely high affinity for binding this trivalent metal ion. The ferric
ion is poorly soluble but it is the form of iron that is predominantly found in oxygenated environments. Siderophore uptake
in bacteria has been extensively studied and over the last decade, detailed structural information for many of the proteins
that are involved in their transport has become available. Specifically, numerous crystal structures for outer membrane siderophore
transporters, as well as for soluble periplasmic siderophore-binding proteins, have been reported. Moreover, unique siderophore-binding
proteins have recently been serendipitously discovered in humans, and the structures of some of their siderophore-complexes
have been characterized. The binding pockets for different ferric-siderophores in these proteins have been described in great
molecular detail. In addition to highlighting this structural information, in this review paper we will also briefly discuss
the relevant chemical properties of iron, and provide a perspective on our current understanding of the human and bacterial
iron uptake pathways. Potential clinical uses of siderophores will also be discussed. The emerging overall picture is that
iron metabolism plays an extremely important role during bacterial infections. Because levels of free ferric iron in biological
systems are always extremely low, there is serious competition for iron and for ferric-siderophores between pathogenic bacteria
and the human or animal host. 相似文献