Fast electron reactions in concentrated solutions of amino acids and nucleotides

A picosecond pulse radiolysis system was used to study the electron attachment processes encountered in concentrated solutions (0.1 to 3 M). These highly concentrated solutions approximate the conditions of a biological cell. The reaction e-/sub aq/ + scavenging molecule has been observed for a range of biologically important molecules. The rate constants depend on the concentration of the solute molecules and the pH of the solution. As well, the initial yield of e-/sub aq/ at 30 psec is reduced markedly in concentrated solutions of scavengers such as amino acids and mononucleotides; the initial process is too fast to be explained by normal chemical kinetics. The scavenger which is unique is the hydrogen ion, H+/sub aq/, which causes no observable reduction of the e-/sub aq/ yields, but has a normal rate constant of reaction with e-/sub aq/. With other electron scavengers, a general relationship between the efficiency of reducing the initial yield of e-/sub aq/ and the rate constant, k/sub e-/sub aq/+S/ in concentrated solutions is obtained. This relationship indicates that both the e-/sub aq/ and its precursor react with the same efficiency toward the solute molecules