Macromolecules, pulse radiolysis

Adams GE, Armstrong RC, Charlesby A, Michael BD, Willson RL (1969) Pulse radiolysis of sulphur compounds, part 3. Repair by hydrogen transfer of a macromolecule irradiated in aqueous solution. Trans Faraday Soc 65 732-742... 

In general, radicals have to terminate bimolecularly. Polymer radicals may react inframolecularly with another radical situated at the same polymer molecule or znfermolecularly with a radical at another polymer molecule. With a large number of radicals at the same macromolecule, such as are produced at the high dose rate of pulse radiolysis and at low polymer concentrations, the former process is usually favored (Fig. 9.1). 

Fig. 9.2. Pulse radiolysis of poly(vinyl alcohol) (10 3 mol dm 3) in N20-saturated aqueous solutions at pH 5.5. Incremental second-order rate constants as a function of a given radical concentration ([R] upper scale) or radicals per macromolecule (Zr lower scale). Open circles 20 Gy open squares 65 Gy filled circles 120 Gy. Source Ulanski et al. (1994), with permission...

The potential of pulse radiolysis for studying biological redox processes, particularly of macromolecules, was recognized rather early. It was initially employed for investigating radiation-induced damage and, later on, as an effective tool for resolving electron transfer processes to and within proteins. Cytochrome c, a well-characterized electron-mediating protein, was the first to be... 

Pulse radiolysis has been employed successfully to resolve mechanisms of action of redox proteins and of electron transfer within their polypeptide matrix. The limitations on the use of this method, set by the requirement for expensive electron accelerators, are more than compensated for by experimental advantages, as illustrated by the results described in this chapter. Future applications to the study of engineered proteins and other model systems would certainly extend our understanding of both of these aspects of redox processes in biological macromolecules. 

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