Application of pulse radiolysis to the study of proteins: chymotrypsin and trypsin

The one-electron reduction of chymotrypsin, trypsin, and their zymogens have been studied by pulse radiolysis. The optical spectra of the transient products from the two active enzymes display a pH-dependent band at 360 nm, associated with the histidine-electron adduct. The yield of the histidyl radical as a function of pH is consistent with a pK(a) less than 4.5, which suggests that the radical is located at the enzyme active site. The histidines of the proenzymes chymotrypsinogen and trypsinogen are unreactive towards the hydrated electron. We conclude that formation of the histidine-electron adduct at the serine protease active site is sensitive to the physical alterations which accompany protease activation

Pulse radiolysis of fast reactions in molecular systems. Progress report, November 1979-September 1980

The rates of elementary chemical reactions in irradiated solutions are being studied by observation of reactive intermediates using the pulse radiolysis technique. Optical absorption spectra of these transient species, which determine the course of the chemistry, are being obtained. The types of reactive species currently of interest are organic molecule ions (both cations and anions) and radical ions, and transition metal carbonyl radicals in solution. Since reaction is initiated by a pulse of high energy electrons, our investigations inherently relate to radiation chemical systems. The information obtained is, however, also of interest in various areas of organic reaction kinetics in which ionic species are known to play a central role. The rectivity of the transition metal carbonyl radicals is of interest in the area of homogeneous catalysis. Current activities involve: spectra and reactivities of transition metal carbonyl radicals of the type M(CO)/sub 5/; reactivity of organic ionic species (including carbocations and carbanions) in irradiated solutions

Pulse radiolysis studies of fast reactions in molecular systems. Progress report, November 1976--October 1977

Results from research in the following two areas are given: formation, properties, and reactivity of molecular ionic species in irradiated liquid systems; and pulse radiolysis of elementary reactions in protein function. (LK