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排序方式: 共有1019条查询结果,搜索用时 15 毫秒
1.
Minjuan Shen Mingli Lin Mengqi Zhu Wenxin Zhang Danyang Lu Huanhuan Liu Jingjing Deng Kehua Que Xu Zhang 《Biochimica et Biophysica Acta (BBA)/General Subjects》2019,1863(1):167-181
Since their discovery, matrix vesicles (MVs) containing minerals have received considerable attention for their role in the mineralization of bone, dentin and calcified cartilage. Additionally, MVs' association with collagen fibrils, which serve as the scaffold for calcification in the organic matrix, has been repeatedly highlighted. The primary purpose of the present study was to establish a MVs–mimicking model (PEG-S-ACP/micelle) in vitro for studying the exact mechanism of MVs-mediated extra/intra fibrillar mineralization of collagen in vivo. In this study, high-concentration serine was used to stabilize the amorphous calcium phosphate (S-ACP), which was subsequently mixed with polyethylene glycol (PEG) to form PEG-S-ACP nanoparticles. The nanoparticles were loaded in the polysorbate 80 micelle through a micelle self-assembly process in an aqueous environment. This MVs–mimicking model is referred to as the PEG-S-ACP/micelle model. By adjusting the pH and surface tension of the PEG-S-ACP/micelle, two forms of minerals (crystalline mineral nodules and ACP nanoparticles) were released to achieve the extrafibrillar and intrafibrillar mineralization, respectively. This in vitro mineralization process reproduced the mineral nodules mediating in vivo extrafibrillar mineralization and provided key insights into a possible mechanism of biomineralization by which in vivo intrafibrillar mineralization could be induced by ACP nanoparticles released from MVs. Also, the PEG-S-ACP/micelle model provides a promising methodology to prepare mineralized collagen scaffolds for repairing bone defects in bone tissue engineering. 相似文献
2.
Defective transducing phages carrying aroG, the structural gene for phenylalanine (phe)-inhibitable phospho-2-keto-heptonate aldolase (EC 4.1.2.15; previously known as 3-deoxy-D-arabinoheptulosonate-7-phosphate synthetase[phe]), have been isolated, and DNA from two of these phages has been used to construct a restriction map of the region from att lambda to aroG. A 7.6-kb PstI-HindIII fragment from one of these phages was cloned into pBR322 and shown to contain aroG. The location of aroG within the 7.6 kb was established by subcloning and Tn3 transpositional mutagenesis. A fragment carrying the aroG promoter and operator has been cloned into a high copy number promoter-cloning vector (pMC489), and the resulting aroGpo-LacZ' (alpha) fusion subcloned in a low copy number vector. Strains with this fusion on the low copy number vector exhibit negative regulation of beta-galactosidase expression by both phenylalanine and tryptophan and positive regulation by tyrosine in a tyrR+ background. 相似文献
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Jean-Vincent Escalant Claude Teisson François Cote 《In vitro cellular & developmental biology. Plant》1994,30(4):181-186
Summary Somatic embryogenesis and plant regeneration of banana and plantain cultivars (Musa spp.) were obtained by culturing young male flowers. Multiplication and maintenance of embryogenic cultures were achieved
by culturing somatic embryos in a temporary immersion system (SIT). A multiplication rate of 40 allowed us to obtain more
than 6000 somatic embryos after 6 mo. of subculture. Plant recovery frequencies were 60 to 70%. This method was expanded to
different banana and plantain genomic groups. 相似文献
6.
Polyethylene glycol was used to induce water stress of micropropagated Valiant grape. Reduced growth and slow rooting were observed in treated plantlets with 2, 4 and 6% polyethylene glycol as compared to control plantlets with no polyethylene glycol in the rooting medium. At high concentrations of 4 and 6%, leaves exhibited wilting and necrosis. At the 2% level, plantlets recovered and grew satisfactorily. Detached leaves of treated plantlets with 2% polyethylene glycol lost less water than controls when exposed to low humidity for 4 hours. Leaf anatomy of plantlets treated with 2% polyethylene glycol, control (in vitro plantlets) and greenhouse-grown plants were compared under light microscopy. Leaves from control plantlets contained larger mesophyll cells, lacked normal palisade layer formation, had greater intercellular pore spaces and fewer chloroplasts. Leaves from polyethylene glycol-treated plantlets, however, had smaller mesophyll cells, a more defined palisade layer, reduced intercellular pore space and the greatest number of chloroplasts. These results suggest that an osmoticum such as polyethylene glycol may be used to induce more normal leaf anatomy and reduced water loss in micropropagated Valiant grapes.Abbreviations BA
6-benzylaminopurine
- FAA
formalin-acetol-alcohol
- MS
Murashige & Skoog (1962) medium
- MW
molecular weight
- NAA
napthaleneacetic acid
- PEG
polyethylene glycol
- TBA
tertiary butyl alcohol 相似文献
7.
在无溶剂系统中固定化脂肪酶合成聚乙二醇400月桂酸酯 总被引:4,自引:1,他引:3
在无溶荆反应系统中,研究了固定化假丝酵母(Candida sp)-1619脂肪酶催化合成聚乙二醇400(PEG400)月桂酸酯的酯化条件。在反应过程中不断脱水和使月桂酸的量高于化学计量值的方法,使酯化率明显提高。分批补加PEG400使产量进一步增加。在5.0mmol月桂酸.2.5mmolPEG400,20mg同定化脂肪酶(200u),O.2ml水组成的反应体系中,40℃,锥形瓶敞口振荡反应48h。醑化率达91%;在负压条件下反应.酯化率达98.9%;反应体系中月桂酸的董增加到6.0mmol时,PEG400完全被酯化。用己烷提取产物的收率为95%.通过薄层色谱鉴定酯化产物为双酯。 相似文献
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In vitro pollen germination of five species and two interspecific hybrids from the genus Brassica was tested in four media. Genetically fixed differences in the demands for optimal pollen germination among species were found. The experiments were designed to define optimal content of mineral salts, sugar, and PEG for every investigated species or hybrids. The differences found among species are discussed in relation to the evolutionary trend. 相似文献
10.
Glenn D. Prestwich Gae E. Kovalick John K. Koeppe 《Biochemical and biophysical research communications》1982,107(3):966-973
The synthesis and testing of several diazocarbonyl JH analogs (diazo JHA) which act as photoaffinity labels for insect juvenile hormone binding proteins are described. The best competitor, 10,11-epoxyfarnesyl diazoacetate, has been shown to irreversibly reduce [3H]-JH III binding to both ovarian and hemolymph JHBP from Leucophaeamaderae after irradiation at 254 nm for 20 seconds. No loss of activity was observed after incubation of JHBP and diazo JHA without irradiation. Protection from photoinactivation by diazo JHA II was achieved by the presence of an equimolar amount of JH III during the photolysis. Photoaffinity labeled proteins show loss of binding capacity without alteration of the binding affinity. This is the first example of the use of a photoaffinity label in the study of JH action on a molecular level, and may become a valuable tool in the elucidation of JH-receptor-chromatin interactions. 相似文献