Radical concentration, effect signal enhancement

Appropriate modification of the ESR spectrometer and generation of free radicals by flash photolysis enables time-resolved (TR) ESR spectroscopy [22]. Spectra observed under these conditions are remarkable for their signal directions and intensities. They can be enhanced as much as one-hundredfold and appear as absorption, emission, or a combination of both. Effects of this type are a result of chemically induced dynamic electron polarization (CIDEP) these spectra indicate the intermediacy of radicals whose sublevel populations deviate substantially from equilibrium populations. Significantly, the splitting pattern characteristic of the spin-density distribution of the intermediate remains unaffected thus, the CIDEP enhancement not only facilitates the detection of short-lived radicals at low concentrations, but also aids their identification. Time-resolved ESR techniques cannot be expected to be of much use for electron-transfer reactions from alkanes, because their oxidation potentials are prohibitively high. Even branched alkanes have oxidation potentials well above the excited-state reduction potential of typical photo-... 

DNA, RNA and nucleotides have a profound effect on the formation and decay of free radical of AA and formation of AA - MM complex (Chlnoy et al., 1974) (ref. Chapter 1). Addition of DNA and RNA to AA In the presence of 2 2 resulted in the enhanced formation of the free radical of AA and Its earlier and faster decay. Enhancement in the signal height varied with the concentration of the nucleic acid and so did the rate of decay. During the reaction of AA with DNA or RNA in the presence of 2 2 observed that... 

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