Electron paramagnetic resonance spectroscopy, rapid-freeze

CEMS = conversion electron Mossbauer spectroscopy DFT = density functional theory EFG = electric field gradient EPR = electron paramagnetic resonance ESEEM = electron spin echo envelope modulation spectroscopy GTO = Gaussian-type orbitals hTH = human tyrosine hydroxylase MIMOS = miniaturized mossbauer spectrometer NFS = nuclear forward scattering NMR = nuclear magnetic resonance RFQ = rapid freeze quench SAM = S -adenosyl-L-methionine SCC = self-consistent charge STOs = slater-type orbitals TMP = tetramesitylporphyrin XAS = X-ray absorption spectroscopy. 

Rapid-mixing rapid-freezing techniques were developed in the 1960s and 1970s. The development was initiated by workers in the field of redox-enzyme biochemistry—at that time in its infancy—to study the role of transition-metal sites in enzyme catalysis by electron paramagnetic resonance (EPR) spectroscopy see Electron Paramagnetic Resonance (EPR) Spectroscopy). Since EPR spectroscopy of transition metals has to be performed, in general, at low temperatures to slow... 

As discussed further in the following sections, there are other variations of rapid mixing/quench methods in which the enzymatic reaction is terminated by freezing the reaction mixture with liquid isopropane. The frozen sample is then analyzed hy electron paramagnetic resonance (EPR), solid-state NMR, or other spectroscopic techniques such as resonance Raman spectroscopy that can accommodate a solid sample. Perhaps the major limitation for implementation of this methodology is the sensitivity of the spectroscopic method and the requirement for large amounts of enzyme. ... 

---