The effect of the Mixing Process on Reaction Kinetics

摘要

If the chemical rate constants of the initial reaction steps are large,any observed value of these constants may be affected by the mixing process.To investigate the effect of mixing efficiency on reaction kinetics we use two previously analyzed reaction systems,namely the glutamic aspartic aminotransferase system and the hemoglobin/O_2 system.A time constant k_a for the mixing process is introduced and four values for this parameter are considered,with the fastest assentially corresponding to complete mixing before any reaction can take place.The remaining three values are associated with mixing instruments,since they may the attainable in the real world.To evaluate the mixing efficiency (and conversely determine underlying k_a values) for observed kinetics,mixing was combined with chemical relaxation by temperature jumps initiated at different points in time during the mixing process.Computer simulations permit the development of specific criteria to determine (in reverse) appropriate values of k_a.In this respect,the aminotransferase system proved to be more revealing than the hemoglobin system.