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The method of affinity coelectrophoresis was used to study the binding of
nine representative glycosaminoglycan (GAG)-binding proteins, all thought
to play roles in nervous system development, to GAGs and proteoglycans
isolated from developing rat brain. Binding to heparin and non-neural
heparan and chondroitin sulfates was also measured. All nine
proteins-laminin-1, fibronectin, thrombospondin-1, NCAM, L1, protease
nexin-1, urokinase plasminogen activator, thrombin, and fibroblast growth
factor-2-bound brain heparan sulfate less strongly than heparin, but the
degree of difference in affinity varied considerably. Protease nexin-1
bound brain heparan sulfate only 1.8- fold less tightly than heparin
(Kdvalues of 35 vs. 20 nM, respectively), whereas NCAM and L1 bound heparin
well (Kd approximately 140 nM) but failed to bind detectably to brain
heparan sulfate (Kd>3 microM). Four proteins bound brain chondroitin
sulfate, with affinities equal to or a few fold stronger than the same
proteins displayed toward cartilage chondroitin sulfate. Overall, the
highest affinities were observed with intact heparan sulfate proteoglycans:
laminin-1's affinities for the proteoglycans cerebroglycan (glypican-2),
glypican-1 and syndecan-3 were 300- to 1800-fold stronger than its affinity
for brain heparan sulfate. In contrast, the affinities of fibroblast growth
factor-2 for cerebroglycan and for brain heparan sulfate were similar.
Interestingly, partial proteolysis of cerebroglycan resulted in a >400-
fold loss of laminin affinity. These data support the views that (1)
GAG-binding proteins can be differentially sensitive to variations in GAG
structure, and (2) core proteins can have dramatic, ligand-specific
influences on protein-proteoglycan interactions.
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Cells cultured on glass substrates have been investigated by phase contrast method. After freeze-thawing the same cells were stained for identification of damage by fluorescent dyes and studied by the phase contrast method, fluorescence and scanning electron microscopy. The method has revealed correlations between the damage of cell surface and the cell damage manifestation at morphological level. 相似文献
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R. D. DRANSFIELD R. BRIGHTWELL J. KIILU M. F. CHAUDHURY D. A. AD ABIE 《Medical and veterinary entomology》1989,3(1):83-95
Seasonal changes in the mean size of tsetse, Glossina pallidipes Austen, as indicated by wing vein length, were monitored during 1983-86 at Nguruman, southwestern Kenya. Changes in size of nulliparous females and wing fray category 1 males were shown to be correlated with the relative humidity 2 months before they were captured. Soil temperature when flies were in the pupal stage had much less effect. Size dependent mortality was demonstrated, with the mean size of flies emerging from pupae significantly less than that of field-caught flies. This mortality must occur at emergence, since there was no evidence of size-dependent mortality once the flies became available to the trap. Size was correlated with density-independent mortality acting on the parent population 2 months previously. It might therefore be possible to use size as an index of the intensity of such mortality. This could be useful when assessing the level of additional mortality required to suppress tsetse populations. 相似文献
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Nuclear DNA sequences from late Pleistocene megafauna 总被引:6,自引:1,他引:5
We report the retrieval and characterization of multi- and single-copy
nuclear DNA sequences from Alaskan and Siberian mammoths (Mammuthus
primigenius). In addition, a nuclear copy of a mitochondrial gene was
recovered. Furthermore, a 13,000-year-old ground sloth and a 33,000-
year-old cave bear yielded multicopy nuclear DNA sequences. Thus, multicopy
and single-copy genes can be analyzed from Pleistocene faunal remains. The
results also show that under some circumstances, nucleotide sequence
differences between alleles found within one individual can be
distinguished from DNA sequence variation caused by postmortem DNA damage.
The nuclear sequences retrieved from the mammoths suggest that mammoths
were more similar to Asian elephants than to African elephants.
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