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排序方式: 共有721条查询结果,搜索用时 31 毫秒
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Mild oxidation promotes and advanced oxidation impairs remodeling of human high-density lipoprotein in vitro 总被引:1,自引:0,他引:1
High-density lipoproteins (HDLs) prevent atherosclerosis by removing cholesterol from macrophages and by exerting antioxidant and anti-inflammatory effects. Oxidation is thought to impair HDL functions, yet certain oxidative modifications may be advantageous; thus, mild oxidation reportedly enhances cell cholesterol uptake by HDL whereas extensive oxidation impairs it. To elucidate the underlying energetic and structural basis, we analyzed the effects of copper and hypochlorite (which preferentially oxidize lipids and proteins, respectively) on thermal stability of plasma spherical HDL. Circular dichroism, light scattering, calorimetry, gel electrophoresis, and electron microscopy showed that mild oxidation destabilizes HDL and accelerates protein dissociation and lipoprotein fusion, while extensive oxidation inhibits these reactions; this inhibition correlates with massive protein cross-linking and with lipolysis. We propose that mild oxidation lowers kinetic barriers for HDL remodeling due to diminished apolipoprotein affinity for lipids resulting from oxidation of methionine and aromatic residues in apolipoproteins A-I and A-II followed by protein cross-linking into dimers and/or trimers. In contrast, advanced oxidation inhibits protein dissociation and HDL fusion due to lipid redistribution from core to surface upon lipolysis and to massive protein cross-linking. Our results help reconcile the apparent controversy in the studies of oxidized HDL and suggest that mild oxidation may benefit HDL functions. 相似文献
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A kinetic study of the interaction of bivalent and monovalent sugar ligands with a lectin was undertaken with the aid of surface
plasmon resonance (SPR) method. The study involved a series of bivalent α-d-mannopyranoside containing sugar ligands, with systematic variation in the distance between the sugar ligands. The detailed
kinetic studies showed that bivalent ligands underwent a faster association (k
on) and a slower dissociation (k
off) of the ligand–lectin complexes, in comparison to the monovalent ligand–lectin complexes. The kinetic constants were complemented
further by assessing the thermodynamic parameters with the aid of isothermal titration calorimetry (ITC). The initiation of
cross-linking of ligand–lectin interactions emerge from the early stages of the complexation. The dynamic light scattering
(DLS) and the transmission electron microscopy (TEM) techniques allowed judging the sizes and morphologies of the complex
in the solution and solid states, respectively. 相似文献
99.
Sambasivam D Liu CW Jayaraman M Malar EJ Rajadas J 《Biochimica et biophysica acta》2008,1784(11):1659-1667
Most of the disease causing proteins such as beta amyloid, amylin, and huntingtin protein, which are natively disordered, readily form fibrils consisting of beta-sheet polymers. Though all amyloid fibrils are made up of beta-sheet polymers, not all peptides with predominant beta-sheet content in the native state develop into amyloid fibrils. We hypothesize that stable amyloid like fibril formation may require mixture of different conformational states in the peptide. We have tested this hypothesis on amyloid forming peptide namely HCl(Ile)(5)NH(CH(2)CH(2)O)(3)CH(3) (I). We show peptide I, has propensity to form self-assembled structures of beta-sheets in aqueous solutions. When incubated over a period of time in aqueous buffer, I self assembled into beta sheet like structures with diameters ranging from 30 to 60 A that bind with amyloidophilic dyes like Congo red and Thioflavin T. Interestingly peptide I developed into unstable fibrils after prolonged aging at higher concentration in contrast with the general mature fibril-forming propensity of various amyloid petides known to date. 相似文献
100.
R. D. Jebakumar Solomon Subramaniam Kallidass Jayaraj Vimalan 《World journal of microbiology & biotechnology》2005,21(6-7):1231-1236
Summary Fresh, dried and powdered samples of leaf, stem and root of Acalypha indica were subjected to fractional distillation in a soxhlet apparatus using solvents such as hexane, chloroform, acetone and methanol.
The plant extracts and a synthetic antifungal compound, Clotrimazole (authentic standard) were subjected to TLC and HPLC analyses.
The Rf (relative front) value of Clotrimazole was 0.371. The plant’s leaf, root and stem extracts also gave distinct spots respectively
at Rf value of 0.371 ± 0.0009. In HPLC, the TLC-separated active compound and Clotrimazole resolved at 1.90 ± 0.2 min (retention
time). The amounts of active compound present in root, leaf and stem extracts were 538, 415 and 171 μg/g respectively. From the results of our study, we infer that the active compound isolated from Acalypha indica is more potent in controlling Candida albicans, Aspergillus niger and Escherichia coli. The Active compound present in the plant had more than 100% activity when compared to standard Clotrimazole. 相似文献