PUB - Publikationen an der Universität Bielefeld

Polyelectrolyte field effects are indicated by particularly large variations of thermodynamic and kinetic constants with ionic strength. Some fundamental principles of local electric field effects in the microenvironment of polyelectrolyte structures are discussed, aiming at a reliable analysis of shifts in equilibrium and rate constants of ionic reaction partners with ionic strength. It is shown that the analytical expressions, within certain limitations, are suitable to determine effective charges involved in polyionic field effects on ionic reactions in the immediate neigborhood of a polyelectrolyte structure. An instructive example for such an observation is the neuro-enzyme acetylcholinesterase. The results of a relaxation-kinetic titration of this anionic enzyme (which hydrolyzes the cationic neuro-activator acetylcholine) with a cationic ligand suggest that the micro environment of the enzyme-active site consists of at least six anionic groups. A large effective, negative charge number is also reflected in the comparatively large association rate coefficients.