Electron spin resonance membranes

A planar BLM cannot be investigated by means of the molecular spectroscopical methods because of the small amount of substance in an individual BLM. This disadvantage is removed for liposomes as they can form quite concentrated suspensions. For example, in the application of electron spin resonance (ESR) a spin-labelled phospholipid is incorporated into the liposome membrane this substance can be a phospholipid with, for example, a 2,2,6,6-tetramethylpiperidyl-A-oxide (TEMPO) group ... 

Marsh, D. 1981. Electron spin resonance Spin labels. In Membrane Spectroscopy. Molecular Biology, Biochemistry, and Biophysics, ed. E. Grell, Vol. 31, pp. 51-142. Berlin, Germany Springer-Verlag. 

Zubenko GS, Kopp U, Seto T, Firestone LL (1999) Platelet membrane fluidity individuals at risk for Alzheimer s disease a comparison of results from fluorescence spectroscopy and electron spin resonance spectroscopy. Psychopharmacology (Berl) 145(2) 175-180... 

The assumption of membrane softness is supported by a theoretical argument of Nelson et al., who showed that a flexible membrane cannot have crystalline order in thermal equilibrium at nonzero temperature, because thermal fluctuations induce dislocations, which destroy this order on long length scales.188 189 The assumption is also supported by two types of experimental evidence for diacetylenic lipid tubules. First, Treanor and Pace found a distinct fluid character in NMR and electron spin resonance experiments on lipid tubules.190 Second, Brandow et al. found that tubule membranes can flow to seal up cuts from an atomic force microscope tip, suggesting that the membrane has no shear modulus on experimental time scales.191 However, conflicting evidence comes from X-ray and electron diffraction experiments on diacetylenic lipid tubules. These experiments found sharp diffraction peaks, which indicate crystalline order in tubule membranes, at least over the length scales probed by the diffraction techniques.123,192 193... 

Retention of a protein or protein activity after 105,000y, 1 hr Chromatography on gel filtration columns with large pore sizes Electron microscopy—however, sample preparation may partially reconstitute membranes Decrease in solution turbidity, which may be detected by a diminution in light scattering or an enhancement in light transmission Diffusion of membrane lipids as assayed by nuclear magnetic resonance and electron spin resonance... 

The effects of ultrasound upon the permeability of the cell walls of the gram-negative bacteria Pseudomonas aeruginosa toward hydrophobic compounds particularly antibiotics have been examined [8]. The penetration and distribution of 16-dosylstearic acid (16-DS) in the cell membranes of the bacteria was quantified by a spin-labeling electron spin resonance (ESR) method. The results indicated that the intracellular concentration of 16- D S was higher in insonated cells and increased linearly with the sonication power. 

Several investigations dealing with the characterization of polymeric membrane systems have been reported lately. A. Kusumi 99> studied phase transitions, fluidity and polarity properties of polymerized and nonpolymerized methacryloyl-derivatized phosphatidylcholine (57) vesicles by DSC and electron spin resonance (ESR). 

MDR cell lines exhibit several other changes in surface membrane properties. Often, the structural order is increased in resistant cells as analyzed by electron spin resonance (ESR) and fluorescence anisotropy studies [98]. In addition, an increase in intramembranous particles and the rate of fluid-phase endocytosis are reported for resistant cells [99, 100]. 

Kadirov MK, Bosnjakovic A, Schlick S (2005) Membrane-derived fluorinated radicals detected by electron spin resonance in UV-irradiated Nation and Dow ionomers effect of counterions and H202. J Phys Chem B 109(16) 7664-70... 

Recently, we have provided evidence that hypoxic reperfusion injury occurs in the inflamed human joint [2,12,13]. Joint movement in patients with RA produces intra-articular pressures in excess of the synovial capillary perfusion pressure. This phenomenon does not occur in normal joints, where the pressure remains subatmospheric throughout a movement cycle. During exercise of the inflamed joint, the intra-articular pressure is transmitted directly to the synovial membrane vasculature, producing occlusion of the superficial synovial capillary bed and ischaemia. Reperfusion of the synovial membrane occurs when exercise is stopped. Recently, electron spin resonance spectroscopy with spin trapping was employed to demonstrate that synovial tissue from a patient with RA generated ROI following a transient hypoxic... 

Shin, Y. K., and Freed, J. H. (1989), Dynamic imaging of lateral diffusion by electron spin resonance and study of rotational dynamics in model membranes. Effect of cholesterol, Biophys. J., 55, 537-550. 

During the last five or ten years many important developments have taken place in photosynthesis research. TTie combined efforts of biochemists and (bio)physicists have now provided a picture of the mechanisms of the photosynthetic reactions and of the structure of the various components of the photosynthetic membrane which is vastly more detailed than might have been envisaged a few years ago. The application of advanced optical instrumentation, both in the visible region (e.g. by laser spectroscopy) and by use of electron spin resonance, has provided a wealth of information concerning the primary reactions of photosynthesis and the inter-... 

Rotational diffusion is characterized by the mean square angular deviation during the time interval At (0 ) = GDrAi. Highly anisotropic motion, which is typical for lipid molecules in the membrane, is usually described by two rotational diffusion coefficients Dr and Dri, which correspond to diffusion about the long diffusion axis and perpendicular to it, respectively. The diffusion coefficients are related to corresponding rotational correlation times measured by nuclear magnetic resonance (NMR), electron spin resonance (ESR), fluorescent depolarization, and so on, as ... 

Shin Y-K, Ewert U, Budil DE, Ereed JH. Microscopic versus macroscopic diffusion in model membranes by electron spin resonance spectral-spatial imaging. Biophys. J. 1991 59 950-957. Trauble H, Sackmann E. Studies of the crystaUine-hquid crystalline phase transition of lipid model membranes, m. Structure of a steroid-lecitin system below and above the hpid-phase transition. J. Am. Chem. Soc. 1972 94 4499-4510. 

To understand the function of membrane-active peptides, it is important to know the structure and orientation of the peptide in the membrane. As is evident from Figure 18.1, it is possible to distinguish between, for example, carpet and pore mechanisms of action by determining the peptide s orientation in the membrane. Various techniques, such as electron spin resonance (ESR) [35], infrared (IR) spectroscopy [36-38], circular dichroism (CD) [35, 39,40], and solid-state NMR (SSNMR) [4-7] are used to investigate membrane-active peptides in a quasi-native lipid bilayer environment. In the following sections, methods to determine peptide structure and orientation are presented. 

Electron spin resonance spectroscopy (ESR), also known as electron paramagnetic resonance (EPR), is based on the property that an unpaired electron placed in a magnetic field shows a typical resonance energy absorption spectrum sensitive to its environment. Recently, this technique, which was primarily developed for biological studies of membrane properties, has been adapted for the study of adsorbed polymer/surfactant layers. The mobility of the ESR probe (stable free radical incorporated into the polymer or surfactant molecule) depends of orientation of the surfactant or polymer and the viscosity of the local environment around the probe. 

These electron spin resonance studies directly show the existence of phase segregation in these ion exchange membranes. The ionic phase is made of the ions, water molecules, and part of the side chains. 

Information about fluidity and viscosity of bilayers of artificial and natural membranes has been obtained from electron spin resonance studies in which the mobility of the spin-labelled species along the surface plane of the membrane is determined (17). However, the monolayer of either lipid, protein, or lipid-protein systems at the air-water interface, makes an ideal model because several parameters can be measured simultaneously. Surface tension, surface pressure, surface potential, surface viscosity, surface fluorescence and microviscosities, surface radioactivity, and spectroscopy may be determined on the same film. Moreover, the films can be picked up on grids from which they may be observed by electron microscopy, studied further for composition, and analyzed for structure by x-ray diffraction and spectroscopy. This approach can provide a clear understanding of the function and morphology of the lipid and lipid-protein surfaces of experimental membranes. However, the first objective is to obtain molecular correlations of surface tension, pressure, potential, and viscosity. 

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