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1.
S Fantappiè A Corsini A Sidoli P Uboldi A Granata T Zanelli P Rossi S Marcovina R Fumagalli A L Catapano 《Journal of lipid research》1992,33(8):1111-1121
We have characterized the epitopes for ten murine monoclonal antibodies (Mabs) to human low density lipoprotein (LDL) and studied their ability to interfere with the LDL-receptor interaction. The epitopes for the antibodies were defined by using the following approaches: 1) interaction with apoB-48; 2) interaction with apoB-100 thrombolytic fragments; and 3) interaction with beta-galactosidase-apoB fusion proteins spanning different areas of the apoB-100 sequence. The results obtained are consistent with the following map of epitopes: Mab 6E, amino acids (aa) 1-1297, Mabs 5A and 6B, aa 1480-1693, Mabs 2A, 7A, 3B, and 4B, aa 2152-2377, Mabs 8A and 9A, aa 2657-3248 and 3H, aa 4082-4306. Four Mabs (2A, 5A, 7A, and 9A) whose epitopes are located in three different areas of apoB, dramatically reduced (up to 95%) the LDL-receptor interaction on cultured human fibroblasts; Fab fragments were as effective as the whole antibodies. Mab 3H, on the other hand, increased LDL binding up to threefold. These findings are consistent with the hypothesis that several areas of apoB-100 are involved independently or in concert in modulating the apoprotein B conformation required for interaction with the LDL receptor. 相似文献
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A L Catapano P K Kinnunen W C Breckenridge A M Gotto R L Jackson J A Little L C Smith J T Sparrow 《Biochemical and biophysical research communications》1979,89(3):951-957
Enzymic hydrolysis of triacylglycerol has been studied with very low density lipoproteins from an individual with a genetically determined absence of apoC-II, the activator apoprotein for lipoprotein lipase. Normal rates of ester cleavage by purified bovine milk lipoprotein lipase can be achieved with native apoC-II and by three shorter synthetic peptides, apoC-II(55–78), apoC-II(50–78) and apoC-II(43–78), which contain part of the carboxyl terminal third of the native apoprotein. At 0.5 μM concentration, all peptides produced a 7-fold activation. ApoC-II(43–78), but not apoC-II(50–78) or apoC-II(55–78), could bind VLDL as shown by separation of unbound 125I peptides and the lipoproteins. Thus, residues 43–50 of apoC-II are part of a lipid binding region. High affinity binding of apoC-II peptides to the lipoprotein substrate is not obligatory for activation of lipoprotein lipase. 相似文献
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When stimulated, rat serosal mast cells degranulate and secrete a cytoplasmic neutral protease, chymase. We studied the fragmentation of apolipoprotein (apo) A-I during proteolysis of HDL(3) by chymase, and examined how chymase-dependent proteolysis interfered with the binding of eight murine monoclonal antibodies (Mabs) against functional domains of apoA-I. Size exclusion chromatography of HDL(3) revealed that proteolysis for up to 24 h did not alter the integrity of the alpha-migrating HDL, whereas a minor peak containing particles of smaller size with prebeta mobility disappeared after as little as 15 min of incubation. At the same time, generation of a large (26 kDa) polypeptide containing the N-terminus of apoA-I was detected. This large fragment and other medium-sized fragments of apoA-I produced after prolonged treatment with chymase were found to be associated with the alphaHDL; meanwhile, small lipid-free peptides were rapidly produced. Incubation of HDL(3) with chymase inhibited binding of Mab A-I-9 (specific for prebeta(1)HDL) most rapidly (within 15 min) of the eight studied Mabs. This rapid loss of binding was paralleled by a similar reduction in the ability of HDL(3) to induce high-affinity efflux of cholesterol from macrophage foam cells, indicating that proteolysis had destroyed an epitope that is critical for this function. In sharp contrast, prolonged degradation of HDL(3) by chymase failed to reduce the ability of HDL(3) to activate LCAT, even though it led to modification of three epitopes in the central region of apoA-I that are involved in lecithin cholesterol acyltransferase (LCAT) activation. This differential sensitivity of the two key functions of HDL(3) to the proteolytic action of mast cell chymase is compatible with the notion that, in reverse cholesterol transport, intactness of apoA-I is essential for prebeta(1)HDL to promote the high-affinity efflux of cellular cholesterol, but not for the alpha-migrating HDL particles to activate LCAT. 相似文献
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1. The increase of species richness with the area of the habitat sampled, that is the species–area relationship, and its temporal analogue, the species–time relationship (STR), are among the few general laws in ecology with strong conservation implications. However, these two scale‐dependent phenomena have rarely been considered together in biodiversity assessment, especially in freshwater systems. 2. We examined how the spatial scale of sampling influences STRs for a Central‐European stream fish assemblage (second‐order Bernecei stream, Hungary) using field survey data in two simulation‐based experiments. 3. In experiment one, we examined how increasing the number of channel units, such as riffles and pools (13 altogether), and the number of field surveys involved in the analyses (12 sampling occasions during 3 years), influence species richness. Complete nested curves were constructed to quantify how many species one observes in the community on average for a given number of sampling occasions at a given spatial scale. 4. In experiment two, we examined STRs for the Bernecei fish assemblage from a landscape perspective. Here, we evaluated a 10‐year reach level data set (2000–09) for the Bernecei stream and its recipient watercourse (third‐order Kemence stream) to complement results on experiment one and to explore the mechanisms behind the observed patterns in more detail. 5. Experiment one indicated the strong influence of the spatial scale of sampling on the accumulation of species richness, although time clearly had an additional effect. The simulation methodology advocated here helped to estimate the number of species in a diverse combination of spatial and temporal scale and, therefore, to determine how different scale combinations influence sampling sufficiency. 6. Experiment two revealed differences in STRs between the upstream (Bernecei) and downstream (Kemence) sites, with steeper curves for the downstream site. Equations of STR curves were within the range observed in other studies, predominantly from terrestrial systems. Assemblage composition data suggested that extinction–colonisation dynamics of rare, non‐resident (i.e. satellite) species influenced patterns in STRs. 7. Our results highlight that the determination of species richness can benefit from the joint consideration of spatial and temporal scales in biodiversity inventory surveys. Additionally, we reveal how our randomisation‐based methodology may help to quantify the scale dependency of diversity components (α, β, γ) in both space and time, which have critical importance in the applied context. 相似文献
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Michael D Kennedy Mark J Haykowsky Carol A Boliek Ben TA Esch Jessica M Scott Darren ER Warburton 《Dynamic medicine : DM》2006,5(1):8