Electron paramagnetic resonance spectroscop

Beth, A.H., Conturo, T.E., Venkataramu, S.D., and Staros, J.V. (1986) Dynamics and interactions of the anion channel in intact human erythrocytes An electron paramagnetic resonance spectroscopic study employing a new membrane-impermeant bifunctional spin-label. Biochemistry 25, 3824-3832. 

Payne, M. j.. Woods, L. F., Gibbs, P., and Cammack, R. (1990). Electron paramagnetic resonance spectroscopic investigation of the inhibition of the phosphoroclastic system of Clostridium sporogenes by nitrite. J. Gen. Microbiol. 136, 2067-2076. 

Scott WG, Murray JB, Arnold JRP, Stoddard BL, King A (1996) Capturing the structure of a catalytic RNA intermediate the hammerhead ribozyme. Science 274(5295) 2065-2069 Horton TE, Clardy DR, DeRose VJ (1998) Electron paramagnetic resonance spectroscopic measurement of Mn binding affinities to the hammerhead ribozyme and correlation with cleavage activity. Biochemistry-US 37(51) 18094—18101... 

Sono M, Andersson LA, Dawson JH (1982) Sulfur donor ligand binding to ferric cytochrome P-450-CAM and myoglobin. Ultraviolet-visible absorption, magnetic circular dichroism, and electron paramagnetic resonance spectroscopic investigation of the complexes. J Biol Chem 257 8308-8320... 

Roland, U., Holzer, F., Poppl, A., and Kopinke, F.-D. (2005) Catalytic and electron paramagnetic resonance spectroscopic characterization of Y-AI2O3 in a non-thermal plasma. /. Adv. Oxid. 

The [NiFe] hydrogenase from D. gigas has been used as a prototype of the [NiFe] hydrogenases. The enzyme is a heterodimer (62 and 26 kDa subunits) and contains four redox active centers one nickel site, one [3Fe-4S], and two [4Fe-4S] clusters, as proven by electron paramagnetic resonance (EPR) and Mosshauer spectroscopic studies (174). The enzyme has been isolated with different isotopic enrichments [6 Ni (I = I), = Ni (I = 0), Fe (I = 0), and Fe (I = )] and studied after reaction with H and D. Isotopic substitutions are valuable tools for spectroscopic assignments and catalytic studies (165, 166, 175). 

In general, several spectroscopic techniques have been applied to the study of NO, removal. X-ray photoelectron spectroscopy (XPS), electron paramagnetic resonance (EPR), nuclear magnetic resonance (NMR), extended X-ray absorption fine structure (EXAFS) and X-ray absorption near-edge structure (XANES) are currently used to determine the surface composition of the catalysts, with the aim to identify the cationic active sites, as well as their coordinative environment. 

Electron paramagnetic resonance (epr) spectroscopic methods are used for the detection and identification of species that have a nett electronic spin radicals, radical ions, etc. It is extremely sensitive, capable of detecting species down to concentration levels of 1 x 10 12 moles dm "3, and produces spectra that are distinctive and generally easily interpreted. Consequently, the technique has found extensive application in electrochemistry since the late 1950s. In order to understand epr, it may be helpful to review some fundamental concepts. 

Most stable ground-state molecules contain closed-shell electron configurations with a completely filled valence shell in which all molecular orbitals are doubly occupied or empty. Radicals, on the other hand, have an odd number of electrons and are therefore paramagnetic species. Electron paramagnetic resonance (EPR), sometimes called electron spin resonance (ESR), is a spectroscopic technique used to study species with one or more unpaired electrons, such as those found in free radicals, triplets (in the solid phase) and some inorganic complexes of transition-metal ions. 

The possibility that there might be long-range electron transfer between redox-active centers in enzymes was first suspected by biochemists working on the mechanism of action of metalloenzymes such as xanthine oxidase which contain more than one metal-based redox center. In these enzymes electron transfer frequently proceeds rapidly but early spectroscopic measurements, notably those by electron paramagnetic resonance, failed to provide any indication that these centers were close to one another. 

Electron-nuclear double resonance (ENDOR) spectroscopy A magnetic resonance spectroscopic technique for the determination of hyperfine interactions between electrons and nuclear spins. There are two principal techniques. In continuous-wave ENDOR the intensity of an electron paramagnetic resonance signal, partially saturated with microwave power, is measured as radio frequency is applied. In pulsed ENDOR the radio frequency is applied as pulses and the EPR signal is detected as a spin-echo. In each case an enhancement of the EPR signal is observed when the radiofrequency is in resonance with the coupled nuclei. 

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