Picosecond reactions of electrons with biologically important molecules

The picosecond pulse radiolysis system has been used to study reactions of the hydrated electron, e-/sub aq/, with high concentrations of scavengers. Reaction rates of many scavengers observed in the picosecond time scale are quite different from that observed in the dilute solution. Moreover, the yield of e-/sub aq/ are drastically reduced in the presence of many scavengers. There is a direct relationship between the reaction rate constant, k, measured in picosecond time region and the efficiency, E, of the scavenger to reduce the initial yield of e-/sub aq/. The hydrated proton H3O/sub aq/+ is an exception to the above correlation. For many ionic dissociable compounds including many amino acids and nucleotides both the k and E vary with the pH of the solution. However, at different pH's, the same relationship still holds between the k and E values. This suggests that the e-/sub aq/ and its precursor are attacking the same sites on many of these scavengers. These results suggest that studies in dilute solutions may not have direct bearing on the radiation chemistry of a living cell