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排序方式: 共有117条查询结果,搜索用时 15 毫秒
1.
Binding of the cationic tetra(tributylammoniomethyl)-substituted hydroxoaluminum phthalocyanine (AlPcN4) to bilayer lipid membranes was studied by fluorescence correlation spectroscopy (FCS) and intramembrane field compensation (IFC) methods. With neutral phosphatidylcholine membranes, AlPcN4 appeared to bind more effectively than the negatively charged tetrasulfonated aluminum phthalocyanine (AlPcS4), which was attributed to the enhancement of the coordination interaction of aluminum with the phosphate moiety of phosphatidylcholine by the electric field created by positively charged groups of AlPcN4. The inhibitory effect of fluoride ions on the membrane binding of both AlPcN4 and AlPcS4 supported the essential role of aluminum-phosphate coordination in the interaction of these phthalocyanines with phospholipids. The presence of negative or positive charges on the surface of lipid membranes modulated the binding of AlPcN4 and AlPcS4 in accord with the character (attraction or repulsion) of the electrostatic interaction, thus showing the significant contribution of the latter to the phthalocyanine adsorption on lipid bilayers. The data on the photodynamic activity of AlPcN4 and AlPcS4 as measured by sensitized photoinactivation of gramicidin channels in bilayer lipid membranes correlated well with the binding data obtained by FCS and IFC techniques. The reduced photodynamic activity of AlPcN4 with neutral membranes violating this correlation was attributed to the concentration quenching of singlet excited states as proved by the data on the AlPcN4 fluorescence quenching. 相似文献
2.
3.
Changes in the position of the minimum of the parabolic capacitance-voltage curve allow the measurement of the amount of ganglioside present in artificial bilayers made with phosphatidylcholine-ganglioside mixtures and asymmetrically shielded with Ca2+. The screening effect of the ionic solution must be considered. With ganglioside/phospholipid molar ratios of up to 15%, all glycolipids can be found at the membrane surfaces. 相似文献
4.
Transport of mercury compounds across bimolecular lipid membranes: effect of lipid composition, pH and chloride concentration 总被引:2,自引:0,他引:2
E Bienvenue A Boudou J P Desmazes C Gavach D Georgescauld J Sandeaux P Seta 《Chemico-biological interactions》1984,48(1):91-101
The use of bimolecular lipid membranes (BLM) as model membrane allows the analysis of the transport of mercury compounds across the lipidic barriers of biological membranes. The results of flux measurements show that two mercury compounds--HgCl2 and CH3HgCl--cross the BLM but the overall permeabilities are dependent on the pH of the aqueous media, and are not apparently influenced by the different phospholipid constituents of the bilayers. On the other hand, electrical measurements show that, function of the chemical speciation, the transport of this metal is done essentially in the neutral form. 相似文献
5.
Voltage-dependent orientation of membrane proteins 总被引:1,自引:0,他引:1
R Blumenthal C Kempf J Van Renswoude J N Weinstein R D Klausner 《Journal of cellular biochemistry》1983,22(1):55-67
In order to study the influence of electrostatic forces on the disposition of proteins in membranes, we have examined the interaction of a receptor protein and of a membrane-active peptide with black lipid membranes. In the first study we show that the hepatic asialoglycoprotein receptor can insert spontaneously into lipid bilayers from the aqueous medium. Under the influence of a trans-positive membrane potential, the receptor, a negatively charged protein, appears to change its disposition with respect to the membrane. In the second study we consider melittin, an amphipathic peptide containing a generally hydrophobic stretch of 19 amino acids followed by a cluster of four positively charged residues at the carboxy terminus. The hydrophobic region contains two positively charged residues. In response to trans-negative electrical potential, melittin appears to assume a transbilayer position. These findings indicate that electrostatic forces can influence the disposition, and perhaps the orientation, of membrane proteins. Given the inside-negative potential of most or all cells, we would expect transmembrane proteins to have clusters of positively charged residues adjacent to the cytoplasmic ends of their hydrophobic transmembrane segments, and clusters of negatively charged residues just to the extracytoplasmic side. This expectation has been borne out by examination of the few transmembrane proteins for which there is sufficient information on both sequence and orientation. Surface and dipole potentials may similarly affect the orientation of membrane proteins. 相似文献
6.
J P Albertini A Garnier-Suillerot L Tosi 《Biochemical and biophysical research communications》1982,104(2):557-563
When Fe(II) is added to a bleomycin. DNA mixture in the presence of air a long-lived EPR silent species (I′) is formed; the circular dichroism and absorption spectra of which have been characterized. This complex slowly decays yielding a ferric complex (III′) analogous to the well known low spin Fe(III). BLM species. 相似文献
7.
A Garnier-Suillerot J P Albertini L Tosi 《Biochemical and biophysical research communications》1981,102(1):499-506
Co(II) interacts with bleomycin in aqueous solution, in the presence of air, to give a short lived mononuclear superoxo-Co(III) complex (I) identified previously, by Sugiura, by electron paramagnetic resonance measurements. This complex rapidly releases O2 to yield the dinuclear μ-peroxo-Co(III) complex (II), but is stabilized by the presence of DNA yielding a new superoxo long lived species (I′). The absorption and circular dichroism spectra of the three species (I,I′,II) have been characterized. 相似文献
8.
Addition of sodium camptothecin (2a, Fig. 1) in comparable low concentrations to the glycopeptide antitumor antibiotic bleomycin (BLM) leads to enhanced rates of single-strand scission of PM2-covalently closed circular DNA, whereas sodium camptothecin alone has no effect. A similar enhancement of DNA scission by sodium camptothecin is produced with the 1 : 1 bleomycin-iron complex alone or in conjunction with NADPH as an additional reductant. The interpretation that camptothecin may substitute for the reducing requirement of the antibiotic is supported by its oxidation at 37°C by the 1 : 1 bleomycin iron complex, by iron salts or more efficiently by hydrogen peroxide to the known hemiacetal (3, Fig. 1).Electrochemical studies of 2a, its analogues and selected model compounds established that the α-pyridone ring D is most susceptible to a one-electron reduction at a reversible potential of ?0.95 ± 0.01 V. The reduced camptothecin is a transient species readily capable of donating an electron. This process may by compatible with a coupled reduction of the sequestered Fe(III) in the glycopeptide antibiotic necessary for the expression of antibiotic and antitumor properties. The results may provide a mechanistic rationale for the observed potentiation of the antitumor activity of bleomycin by camptothecin in vivo. 相似文献
9.
Y Sugiura 《Biochemical and biophysical research communications》1979,87(2):643-648
On the basis of electron spin resonance results, the 1:1 Cu(II), Co(II), Co(II)-O2, and Ni(III) complexes of bleomycin(BLM) have been compared with the corresponding metal complexes of its biosynthetic intermediate(P-3A). The present study suggests that (1) P-3A is an useful ligand for the clarification of metal-binding sites of BLM; (2) the secondary amine, pyrimidine ring nitrogen, deprotonated peptide nitrogen of histidine residue, and histidine imidazole groups as planar ligand donors, and the α-amino group as axial donor, are substantially important for metal-coordination of BLM; and (3) the sugar and bithiazole portions of BLM probably contribute to stabilization of Co(II)-O2 adduct complex and axial sixth coordination of Cu(II) and Ni(III) complexes. 相似文献
10.
Ioanna Sevastou Eleanna KaffeMarios-Angelos Mouratis Vassilis Aidinis 《Biochimica et Biophysica Acta (BBA)/Molecular and Cell Biology of Lipids》2013,1831(1):42-60
Lysophosphatidylcholine (LPC) and lysophosphatidic acid (LPA), the most prominent lysoglycerophospholipids, are emerging as a novel class of inflammatory lipids, joining thromboxanes, leukotrienes and prostaglandins with which they share metabolic pathways and regulatory mechanisms. Enzymes that participate in LPC and LPA metabolism, such as the phospholipase A2 superfamily (PLA2) and autotaxin (ATX, ENPP2), play central roles in regulating LPC and LPA levels and consequently their actions. LPC/LPA biosynthetic pathways will be briefly presented and LPC/LPA signaling properties and their possible functions in the regulation of the immune system and chronic inflammation will be reviewed. Furthermore, implications of exacerbated LPC and/or LPA signaling in the context of chronic inflammatory diseases, namely rheumatoid arthritis, multiple sclerosis, pulmonary fibrosis and hepatitis, will be discussed. This article is part of a Special Issue entitled Advances in Lysophospholipid Research. 相似文献