Electron paramagnetic resonance relaxation metals

The substitution of a different metal into an enzyme provides a very useful method for studying the immediate environment of the metal site. In addition to the use of Co2 for spectral studies, appropriate substitution allows the use of physical methods such as electron paramagnetic resonance (Co . Cu2 ). the Mdssbauer effect tFe2 ). proton magnetic resonance relaxation techniques (Mir ), or X-ray crystallography (with a heavy metal atom to aid in the structure solution). ... 

Electron paramagnetic resonance (EPR) Quadrupole tensor, nuclear Zeeman splitting, g values, coupling constants, relaxation times Usually for odd electron metal sites probes ground-state wave function at high resolution... 

The electron spin resonance (ESR) technique has been extensively used to study paramagnetic species that exist on various solid surfaces. These species may be supported metal ions, surface defects, or adsorbed molecules, ions, etc. Of course, each surface entity must have one or more unpaired electrons. In addition, other factors such as spin-spin interactions, the crystal field interaction, and the relaxation time will have a significant effect upon the spectrum. The extent of information obtainable from ESR data varies from a simple confirmation that an unknown paramagnetic species is present to a detailed description of the bonding and orientation of the surface complex. Of particular importance to the catalytic chemist... 

In order to characterize the active site structure of Ca ATPase from sarcoplasmic reticulum, we have employed Gd + as a paramagnetic probe of this system in a series of NMR and EPR investigations. Gadolinium and several other lanthanide ions have been used in recent years to characterize Ca + (and in some cases Mg2+) binding sites on proteins and enzymes using a variety of techniques, including water proton nuclear relaxation rate measurements (35,36,37), fluorescence (38) and electron spin resonance (39). In particular Dwek and Richards (35) as well as Cottam and his coworkers (36,37) have employed a series of nuclear relaxation measurements of both metal-bound water protons and substrate nuclei to characterize the interaction of Gd + with several enzyme systems. 

W28. Wong, S. K., and Wan, J. K. S., Analysis of paramagnetic metal ions of low sensitivity by electron spin resonance utilisation of cross relaxation phenomena. Anal. Lett. 4, 701-707 (1971). 

Electronic relaxation times of some common paramagnetic metal ions and nuclear relaxation rates for a proton at 5 A from the metal, at 800 MHz H resonance frequency, due to dipolar and Curie relaxation, estimated from Eqs. (3.16), (3.17), (3.29) and (3.30), with rc = rs... 

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