Dr. Cornelia Bohne, WUESP Visiting Speaker

"Supramolecular Dynamics and Function from Macrocycles to Gels and Proteins"

Abstract

Supramolecular systems are always reversible and characterization of their dynamics is essential to understand and control their function. The kinetics for the association and dissociation processes of the building blocks of interest are measured using fast kinetic techniques. Studies with host systems of increasing complexity will be presented: (i) The characterization of the binding dynamics of a chiral guest with cyclodextrin uncovered the reasons for chiral recognition from the kinetic studies. (ii) Studies with cucurbit[n]urils (CB[n]) showed that the exceptionally high equilibrium constants for guest binding are achieved because the dissociation processes are much slower than observed for other macrocycles. The presence of cations, which can bind to the portals of CB[n]s, and the structure of the guest influence the type of mechanism observed for the guest-CB[n] dynamics. (iii) Bile salt aggregates are host systems with increased complexity because of the presence of binding sites with different properties. Bile salt aggregates in solution and as gels are excellent hosts to solubilize water insoluble functional guests, such as photochromic compounds.( iv) Serum albumins are chiral host systems that were employed to enhance the chiral discrimination of a bimolecular model reaction. Photophysical measurements showed that the highest enantiomeric excess is achieved when the reagent is bound to a protein site for which exchange dynamics of the reagent with the aqueous phase is fast, but once bound the reagent is immobile.