Labeling 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. 

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. 

Montesano, G., Bartucci, R., Belsito, S., Marsh, D., and Sportelli, L. 2001. Lipid membrane expansion and micelle formation by polymer-grafted lipids Scaling with polymer length studied by spin-label electron spin resonance. Biophys. J. 80 1372. 

The effectiveness of a crude oil demulsifier is correlated with the lowering of the shear viscosity and the dynamic tension gradient of the oil-water interface. The interfacial tension relaxation occurs faster with an effective demulsifier [1714]. Short relaxation times imply that interfacial tension gradients at slow film thinning are suppressed. Electron spin resonance experiments with labeled demulsifiers indicate that the demulsifiers form reverse micellelike clusters in the bulk oil [1275]. The slow unclustering of the demulsifier at the interface appears to be the rate-determining step in the tension relaxation process. 

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 ... 

As with the nitroxalkylcobalamins (119) and cobinamides, the co-binamides in which nitroxide is coordinated show electron spin resonance spectra very similar to the spectrum of free nitroxide. The high field line is not broadened as much as in the spectrum of a nitroxalkyl-cobinamide. No hyperfine splitting from methyl protons in the 2 or 6 positions can be observed for the bound nitroxide. However, treatment of the coordinate spin labeled compounds with cyanide releases the nitroxide. When this happens, the proton hyperfine can be observed (Fig. 25). Thus treatment with cyanide simply displaces the nitroxide and a spectrum for free nitroxide is observed. 

We have studied demulsifier association by the electron spin resonance (ESR) technique. The spin label is covalently attached (Figure 5a) to the demulsifier. Normally, the ESR spectrum of a freely tumbling nitroxyl radical consists of three sharp peaks (Figure 5b). However, the spectrum for a tagged ethoxylated nonyl phenol resin (Figure 6a or 6b) shows only a single broad peak. 

For effective demulsification of a water-in-oil emulsion, both shear viscosity as well as dynamic tension gradient of the water-oil interface have to be lowered. The interfacial dilational modulus data indicate that the interfacial relaxation process occurs faster with an effective demulsifier. The electron spin resonance with labeled demulsifiers suggests that demulsifiers form clusters in the bulk oil. The unclustering and rearrangement of the demulsifier at the interface may affect the interfacial relaxation process. 

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. 

Subczynski, W. K. and J. S. Hyde. 1984. Diffusion of oxygen in water and hydrocarbons using an electron spin resonance spin-label technique. Biophys. J. 45 743-748. 

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]. 

Several other analytical procedures exist in which solvent extraction may be applied. Thus extraction has been used in a limited number of analyses with procedures such as (1) luminescence (fluorimetry), where, for example, the detection limit of rhodamine complexes of gallium or indium can be increased by extraction [28] (2) electron spin resonance using a spin-labelled extractant [29] and (3) mass spectrometry, where an organic extract of the analyte is evaporated onto pure AI2O3 before analysis [30]. 

A stable paramagnetic group that has been attached to a molecular entity. Experiments with ESR measurements can reveal aspects of the microenvironment of the spin label. If the paramagnetic group is not covalently attached to the molecular entity of interest, the term spin probe is usually applied. See also Electron Spin Resonance... 

Considerable international effort has since been directed towards these goals and substantial progress has been made in a number of directions. The development of accepted detection procedures not only gives enforcement authorities the ability to check that products are correctly labelled but also gives the consumer confidence that adequate independent controls are available. Perhaps the detection method that is, to date, the most internationally accepted is Electron Paramagnetic Resonance (EPR) spectroscopy which can also be referred to as Electron Spin Resonance (ESR) spectroscopy. 

The activity of lyophilized HL-ADH in several solvents increased by orders of magnitude upon addition of small amounts of water to solvents of dielectric constant e from 1.9 to 36 (Guinn, 1991). Enzyme flexibility, as measured by electron spin resonance (ESR) spectroscopy with a spin label at the active site, did not depend on water content but on of the pure solvent HL-ADH turns less flexible with decreasing . 

Electron spin resonance (ESR) spectroscopy is much more sensitive than NMR but one is, of course, strongly hampered by the requirement of unpaired electrons. The study of nitroxide-labelled compounds, both surfactants and solubilizates, has... 

Fajer, P. G. (2000). Electron spin resonance spectroscopy labeling in proteins and peptides analysis. In Encyclopedia of Analytical Chemistry, (R. Meyers, ed.), pp. 5725-5761. Wiley, Chichester. 

Spin immunoassay is also a type of homogeneous immunoassay. A change in the electron spin resonance (ESR) spectrum of a spin (marker)-labeled... 

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