scholarly journals Chemiluminescence of lipid vesicles supplemented with cytochrome c and hydroperoxide

1980 ◽  
Vol 188 (3) ◽  
pp. 577-583 ◽  
Author(s):  
E Cadenas ◽  
A Boveris ◽  
B Chance
Keyword(s):  
Cytochrome C ◽  
Light Emission ◽  
Lipid Vesicles ◽  
Soya Bean ◽  
Phase Iii ◽  
Lipid Vesicle ◽  
Present System ◽  
Dipalmitoyl Phosphatidylcholine ◽  
Radical Trap ◽  
Enhanced Chemiluminescence

The increase in light emission of hydroperoxide-supplemented cytochrome c observed on addition of lipid vesicles was related to the degree of unsaturation of the fatty acids of the phospholipids: dipalmitoyl phosphatidylcholine was without effect, whereas dioleoyl phosphatidylcholine and soya-bean phosphatidylcholine enhanced chemiluminescence 2- and 3-fold respectively. Effects on light-emission were similar to those on O2 uptake. The chemiluminescence of the present system was sensitive to cyanide and to the radical trap 2,5-di-t-butylquinol, indicating a catlytic activity of cytochrome c and the presence of free-radical species respectively. Lipid-vesicle enhanced chemiluminescence showed different kinetic behaviours, apparently depending on unsaturation: three phases are described for soya-bean phosphatidylcholine, whereas only one phase was present in mixtures containing dipalmitoyl and dioleoyl phospholipids. Chemiluminescence of lipid vesicles supplemented with cytochrome c and hydroperoxide showed similar kinetic patterns with H2O2 and primary (ethyl) and tertiary (t-butyl and cumene) hydroperoxides. Participation of singlet molecular oxygen, mainly on the phase III of chemiluminescence, is suggested by the increase of light-emission by 1,4-diazabicyclo[2.2.2]-octane as well as by data from spectral analysis.

scholarly journals Low-level chemiluminescence of hydroperoxide-supplemented cytochrome c

1980 ◽  
Vol 187 (1) ◽  
pp. 131-140 ◽  
Author(s):  
Enrique Cadenas ◽  
Alberto Boveris ◽  
Britton Chance
Keyword(s):  
Cytochrome C ◽  
Singlet Oxygen ◽  
Light Emission ◽  
Cumene Hydroperoxide ◽  
Present System ◽  
Butyl Hydroperoxide ◽  
Low Level ◽  
Radical Trap ◽  
Organic Hydroperoxides ◽  
Ferricytochrome C

Ferricytochrome c showed low-level chemiluminescence, with a light-emission measured of about 1×103–3×103 counts/s, when supplemented with organic hydroperoxides. Tertiary hydroperoxides (cumene hydroperoxide and t-butyl hydroperoxide) showed a saturation behaviour at about 5mm-hydroperoxide, whereas primary hydroperoxides showed a quadratic dependence on the hydroperoxide concentration. Chemiluminescence depended linearly on cytochrome c concentration, and optimal light-emission was observed at [t-butyl hydroperoxide]/[ferricytochrome c] ratios of 160–500. Hydroperoxide-supplemented ferricytochrome c consumed O2 at a rate of 1.0μmol/min per μmol of cytochrome c; the rate of O2 uptake was linearly related to the concentration of cytochrome c. The Soret absorption band of ferricytochrome c decreased about 64% after incubation with t-butyl hydroperoxide, whereas the 530nm band was almost totally abolished. Light-emission was (a) inhibited competitively by cyanide. (b) inhibited by singlet-oxygen quenchers (e.g. β-carotene), scavengers (e.g. dimethylfuran) and traps (e.g. histidine and tryptophan) and (c) increased by singlet-oxygen-chemiluminescence enhancer 1,4-diazabicyclo[2.2.2]-octane. Superoxide dismutase had no effect on the present system. The participation of free radicals is suggested by the effect of the radical trap 2,5-di-t-butylquinol. Singlet-oxygen dimol emission seems to be mainly responsible for the observed light-emission; a mechanism that can account for the major part of the present experimental observations is proposed.

scholarly journals Fast Simulation of Lipid Vesicle Deformation Using Spherical Harmonic Approximation

2016 ◽  
Vol 21 (1) ◽  
pp. 40-64
Author(s):  
Michael Mikucki ◽  
Yongcheng Zhou
Keyword(s):  
Harmonic Functions ◽  
Degrees Of Freedom ◽  
Finite Difference Methods ◽  
Harmonic Approximation ◽  
Lipid Vesicles ◽  
Membrane Curvature ◽  
Lipid Vesicle ◽  
Nonlinear Conjugate Gradient Method ◽  
Surface Harmonic ◽  
Curvature Energy

AbstractLipid vesicles appear ubiquitously in biological systems. Understanding how the mechanical and intermolecular interactions deform vesicle membranes is a fundamental question in biophysics. In this article we develop a fast algorithm to compute the surface configurations of lipid vesicles by introducing surface harmonic functions to approximate themembrane surface. This parameterization allows an analytical computation of the membrane curvature energy and its gradient for the efficient minimization of the curvature energy using a nonlinear conjugate gradient method. Our approach drastically reduces the degrees of freedom for approximating the membrane surfaces compared to the previously developed finite element and finite difference methods. Vesicle deformations with a reduced volume larger than 0.65 can be well approximated by using as small as 49 surface harmonic functions. The method thus has a great potential to reduce the computational expense of tracking multiple vesicles which deform for their interaction with external fields.

Detection of superoxide anion released extracellularly by endothelial cells using cytochrome c reduction, ESR, fluorescence and lucigenin-enhanced chemiluminescence techniques

2000 ◽  
Vol 29 (5) ◽  
pp. 388-396 ◽  
Author(s):  
Marie-Aline Barbacanne ◽  
Jean-Pierre Souchard ◽  
Benoit Darblade ◽  
Jean-Pierre Iliou ◽  
Françoise Nepveu ◽  
...  
Keyword(s):  
Endothelial Cells ◽  
Cytochrome C ◽  
Superoxide Anion ◽  
Enhanced Chemiluminescence ◽  
Cytochrome C Reduction

Deformation and rupture of lipid vesicles in the strong shear flow generated by ultrasound-driven microbubbles

2008 ◽  
Vol 464 (2095) ◽  
pp. 1781-1800 ◽  
Author(s):  
Philippe Marmottant ◽  
Thierry Biben ◽  
Sascha Hilgenfeldt
Keyword(s):  
Shear Flow ◽  
Acoustic Streaming ◽  
Three Dimensional ◽  
Spherical Shape ◽  
Lipid Vesicles ◽  
Boundary Integral ◽  
Elastic Response ◽  
Lipid Vesicle ◽  
Strong Shear ◽  
Vesicle Rupture

Considering the elastic response of the membrane of a lipid vesicle (artificial cell) in an arbitrary three-dimensional shear flow, we derive analytical predictions of vesicle shape and membrane tension for vesicles close to a spherical shape. Large amplitude deviations from sphericity are described using boundary integral numerical simulations. Two possible modes of vesicle rupture are found and compared favourably with experiments: (i) for large enough shear rates the tension locally exceeds a rupture threshold and a pore opens at the waist of the vesicle and (ii) for large elongations the local tension becomes negative, leading to buckling and tip formation near a pole of the vesicle. We experimentally check these predictions in the case of strong acoustic streaming flow generated near ultrasound-driven microbubbles, such as those used in medical applications.

Filaments of surfactant protein A specifically interact with corrugated surfaces of phospholipid membranes

1999 ◽  
Vol 276 (4) ◽  
pp. L631-L641 ◽  
Author(s):  
Nades Palaniyar ◽  
Ross A. Ridsdale ◽  
Stephen A. Hearn ◽  
Yew Meng Heng ◽  
F. Peter Ottensmeyer ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Protein A ◽  
Lipid Vesicles ◽  
Surfactant Protein ◽  
Uranyl Acetate ◽  
Lipid Vesicle ◽  
Transmission Electron

Pulmonary surfactant, a mixture of lipids and surfactant proteins (SPs), plays an important role in respiration and gas exchange. SP-A, the major SP, exists as an octadecamer that can self-associate to form elongated protein filaments in vitro. We have studied here the association of purified bovine SP-A with lipid vesicle bilayers in vitro with negative staining with uranyl acetate and transmission electron microscopy. Native bovine surfactant was also examined by transmission electron microscopy of thinly sectioned embedded material. Lipid vesicles made from dipalmitoylphosphatidylcholine and egg phosphatidylcholine (1:1 wt/wt) generally showed a smooth surface morphology, but some large vesicles showed a corrugated one. On the smooth-surfaced vesicles, SP-As primarily interacted in the form of separate octadecamers or as multidirectional protein networks. On the surfaces of the striated vesicles, SP-As primarily formed regularly spaced unidirectional filaments. The mean spacing between adjacent striations and between adjacent filaments was 49 nm. The striated surfaces were not essential for the formation of filaments but appeared to stabilize them. In native surfactant preparations, SP-A was detected in the dense layers. This latter arrangement of the lipid bilayer-associated SP-As supported the potential relevance of the in vitro structures to the in vivo situation.

scholarly journals Interaction of phospholipid vesicles with cultured mammalial cells. I. Characteristics of uptake.

1975 ◽  
Vol 67 (1) ◽  
pp. 38-48 ◽  
Author(s):  
L Huang ◽  
R E Pagano
Keyword(s):  
Chinese Hamster ◽  
Lipid Vesicles ◽  
Metabolic Inhibitors ◽  
Lipid Vesicle ◽  
Lipid Phase ◽  
Lipid Uptake ◽  
V79 Cells ◽  
Prolonged Incubation ◽  
Exogenous Lipid ◽  
Effects Of Ph

The interaction of monolayer cultures of Chinese hamster V79 cells with artificially generated, unilamellar lipid vesicles (approximately 500 A diameter) was examined. Vesicles prepared from a variety of natural and synthetic radiolabeled phosphatidyl cholines (lecithins) were incubated with V79 cells bathed in a simple balanced salt solution. After incubation, the cells were analyzed for exogenous lipid incorporation. Large quantities (approximately 10(8) molecules/cell/h) of lecithin became cell associated without affecting cell viability. The effects of pH, charged lipids, and the influence of the vesicle lipid phase transition on the uptake process were examined. Glutaraldehyde fixation of cells before vesicle treatment, or incubation in the presence of metabolic inhibitors, failed to reduce the lecithin uptake by more than 25-50%, suggesting that the lipid uptake is largely energy independent. Cells in sparse culture took up about ten times more lipid than dense cultures. Prolonged incubation (greater than 15 h) of sparse cell cultures with lecithin vesicles resulted in significant cell death while no deleterious effect was found in dense cultures, or with 1:1 lecithin/cholesterol vesicles. When vesicle-treated cells were homogenized and fractionated, about 20-30% of the exogenous lipid was found in the plasma membrane fraction, with the remainder being distributed into intracellular fractions. Electron microscope radioautography further demonstrated that most of the internalized lipid was present in the cytoplasm, with little in the nucleus. These results are discussed in terms of possible modification of cell behavior by lipid vesicle treatment.

scholarly journals X-ray scattering from unilamellar lipid vesicles

2005 ◽  
Vol 38 (1) ◽  
pp. 126-131 ◽  
Author(s):  
Michael R. Brzustowicz ◽  
Axel T. Brunger
Keyword(s):  
Form Factor ◽  
Lipid Bilayer ◽  
Electron Density ◽  
Lipid Vesicles ◽  
Lipid Vesicle ◽  
Asymmetric Structure ◽  
Bilayer Structure ◽  
X Ray ◽  
X Ray Scattering ◽  
Ray Scattering

An improved small-angle X-ray scattering (SAXS) method for determining asymmetric lipid bilayer structure in unilamellar vesicles is presented. From scattering theory, analytic expressions are derived for the bilayer form factor over flat and spherical geometries, assuming the lipid bilayer electron density to be composed of a series of Gaussian shells. This is in contrast to both classic diffraction and Guinier hard-shell SAXS methods which, respectively, are capable only of ascertaining symmetric bilayer structure and limited-resolution asymmetric structure. Using model fitting and direct calculation of the form factor, using only one equation, an asymmetric electron density profile of the lipid vesicle is obtained with high accuracy, as well as the average radius. The analysis suggests that the inner leaflet of a unilamellar lipid vesicle is `rougher' than the outer one.

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