Lipid electron spin resonance

ANDERSEN M L and SKIBSTED L H (2002) Detection of early events in lipid oxidation by electron spin resonance spectroscopy, Eur J Lipid Sci Technol, 104, 65-8. 

Matsuo, M. Matsumoto, S. Electron spin resonance spectra of the chromanoxyl radicals derived from tocopherols (vitaminE) and theirrelated compounds. Lipids 1983,18, 81-86. 

Mukai, K. Tsuzuki, N. Ouchi, S. Fukuzawa, K. Electron spin resonance studies of chromanoxyl radicals derived from tocopherols. Chem. Phys. Lipids 1982, 30, 337-345. 

Tsuchija, J. Niki, E. Kamiya, Y. Oxidation of lipids IV. Formation and reaction of chromanoxyl radicals as studied by electron spin resonance. Bull. Chem. Soc. Jpn. 1983, 56, 229-232. 

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... 

Less frequently used at present is electron spin resonance spectroscopy, which is based on the use of spin probes as model componnds or covalent spin labeling of drugs. Microviscosity and micropolarity of the molecnlar environment of the probe can be derived from electron spin resonance spectra. Moreover, the spectra allow us to differentiate isotropic and anisotropic movements, which result from the incorporation of the probe into liposomal structures. Quantitative distribution of the spin probes between the internal lipid layer, the snrfactant, and the external water phase is to be determined noninvasively. On the basis of the chemical degradation of drugs released from the lipid compartment, agents with reductive features (e.g., ascorbic acid) allow us to measure the exchange rate of the drugs between lipophilic compartments and the water phase [27,28]. 

Simon, I., C. P. Burns, and A. A. Spector. Electron spin resonance studies on intact cells and isolated lipid... 

It is evident that all the described methods are based on reduction reactions. Substrates react either with long-living radicals (TEAC, TRAP), AOC (ORAC) or with the iron complex compound (FRAP), AOM concentration are obtained as a result of enzymatic reactions [51] or their existing level is registered with electron-spin resonance [52], Various modifications of peroxidation lipid reaction can also be applied [53],... 

Rehfeld, S.J., et al. 1988. Calorimetric and electron spin resonance examination of lipid phase transitions in human stratum corneum Molecular basis for normal cohesion and abnormal desquamation in recessive X-linked ichthyosis. J Invest Dermatol 91 499. 

Pali, T., Finbow, M. E., Holzenburg, A., Findlay, J. B., and Marsh, D. (1995). Lipid-protein interactions and assembly of the 16-kDa channel polypeptide from Nephrops norvegicus Studies with spin-label electron spin resonance spectroscopy and electron microscopy. Biochemistry 34, 9211-9218. 

In recent years, modern instrumental methods have been developed to monitor lipid oxidation in biological samples, including dairy products. These include use of electron spin resonance (ESR) spectrometry, direct measurement of secondary oxidative products such as malonaldehyde, static and dynamic GC/MS methods. ESR spectrometry permits detection of free radicals formed in the very early stages of oxidation prior to the formation of peroxides. The method has been applied successfully to dairy products such as milk powders and processed cheese (Nielsen et al., 1997 Stapelfeldt... 

From the analysis of the data in the LIPID AT database (41), more than 150 different methods and method modifications have been used to collect data related to the lipid phase transitions. Almost 90% of the data is accounted for by less than 10 methods. Differential scaiming calorimetry strongly dominates the field with two thirds of all phase transition records. From the other experimental techniques, various fluorescent methods account for 10% of the information records. X-ray diffraction, nuclear magnetic resonance (NMR), Raman spectroscopy, electron spin resonance (ESR), infrared (IR) spectroscopy, and polarizing microscopy each contribute to about or less than 2-3% of the phase transition data records in the database. Especially useful in gaining insight into the mechanism and kinetics of lipid phase transitions has been time-resolved synchrotron X-ray diffraction (62,78-81). 

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. 

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