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排序方式: 共有70条查询结果,搜索用时 4 毫秒
1.
Stereochemistry of cooperative effects in haemoglobin 总被引:136,自引:0,他引:136
M F Perutz 《Nature》1970,228(5273):726-739
2.
Selective functionalization of mesoporous silica nanospheres (MSNs) is crucial for nanoengineering of MSNs.
Herein, we have combined “surface-protected etching strategy” and “cationic surfactant assisted etching
strategy” to prepare functionalized MSNs with externally attached amino groups. The externally attached NH2
groups endow the catalysts with excellent catalytic performance for nitroaldol reaction between nitromethane
and benzaldehyde. In addition, those NH2-MSNs can also be used to support gold nanoparticles, which display
very good catalytic performance for reduction of 4-nitrophenol. It can be envisioned that the synthesis protocol
developed in this work could also be extended to nanoengineered MSNs, which provides opportunities for nanoreactors
design. 相似文献
3.
4.
Although jawless vertebrates are apparently capable of adaptive immune responses, they have not been found to possess the recombinatorial antigen receptors shared by all jawed vertebrates. Our search for the phylogenetic roots of adaptive immunity in the lamprey has instead identified a new type of variable lymphocyte receptors (VLRs) composed of highly diverse leucine-rich repeats (LRR) sandwiched between amino- and carboxy-terminal LRRs. An invariant stalk region tethers the VLRs to the cell surface by means of a glycosyl-phosphatidyl-inositol anchor. To generate rearranged VLR genes of the diversity necessary for an anticipatory immune system, the single lamprey VLR locus contains a large bank of diverse LRR cassettes, available for insertion into an incomplete germline VLR gene. Individual lymphocytes express a uniquely rearranged VLR gene in monoallelic fashion. Different evolutionary strategies were thus used to generate highly diverse lymphocyte receptors through rearrangement of LRR modules in agnathans (jawless fish) and of immunoglobulin gene segments in gnathostomes (jawed vertebrates). 相似文献
5.
The spin of a single electron subject to a static magnetic field provides a natural two-level system that is suitable for use as a quantum bit, the fundamental logical unit in a quantum computer. Semiconductor quantum dots fabricated by strain driven self-assembly are particularly attractive for the realization of spin quantum bits, as they can be controllably positioned, electronically coupled and embedded into active devices. It has been predicted that the atomic-like electronic structure of such quantum dots suppresses coupling of the spin to the solid-state quantum dot environment, thus protecting the 'spin' quantum information against decoherence. Here we demonstrate a single electron spin memory device in which the electron spin can be programmed by frequency selective optical excitation. We use the device to prepare single electron spins in semiconductor quantum dots with a well defined orientation, and directly measure the intrinsic spin flip time and its dependence on magnetic field. A very long spin lifetime is obtained, with a lower limit of about 20 milliseconds at a magnetic field of 4 tesla and at 1 kelvin. 相似文献
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8.
Arianne Monge Naldi Max Gassmann Daniel Bodmer 《Cellular and molecular life sciences : CMLS》2009,66(22):3595-3599
It has recently been shown that the oxygen-regulated factors erythropoietin (Epo) and vascular endothelial growth factor (VEGF)
confer protection on different cells, including neuronal-derived ones. The receptors for Epo and VEGF are widely expressed
in different organs. Since mammalian auditory hair cells can irreversibly be damaged by different agents, we aimed to identify
otoprotective compounds. We focused on the role of Epo and VEGF in the inner ear and review the recent studies. Epo and its
receptor are expressed in the inner ear. In vitro experiments on auditory hair cells showed a protective effect of Epo in
ischemia- and gentamicin-induced hair cell damage. In contrast, an in vivo study using an animal model of noise-induced hearing
loss showed a negative effect of Epo. Also VEGF and its receptors are expressed in the inner ear. Changes in the expression
of VEGF or its receptors have been found in the cochlea after noise exposure, transcranial vibration and diabetic or aged
animals. Until now, there are no studies about a direct effect of VEGF on auditory hair cells in vitro or in vivo. We could
exclude a protective effect of VEGF on gentamicin-induced auditory hair cell damage in vitro. Thus, we conclude that Epo but
not VEGF has a protective effect on auditory hair cell damage at least in vitro. (Part of a multi-author review.) 相似文献
9.
Allosteric enzymes. Control by phosphorylation 总被引:1,自引:0,他引:1
M F Perutz 《Nature》1988,336(6196):202-203
10.
Molecular pathology of human haemoglobin 总被引:47,自引:0,他引:47