Intermolecular Forces: Understanding The True Nature Of The Pfeiffer Effect

       Working under the hypothesis that the Pfeiffer effect is influenced by intermolecular interactions between a lanthanide(III)  complex and an added chiral amino acid, we have manipulated various factors such as pH, solvent, and ionic strength in order to establish the groundwork for fully understanding these complex interactions. Understanding these relationships will aid us in similar chiral recognition studies involving other biologically significant molecules.

   Circularly polarized luminescence spectroscopy was used to probe the perturbation of a lanthanide(III) complex existing as a racemic equilibrium in solution by the addition of chiral molecules such as amino acids (i.e. L/D-proline or L/D-serine). Several experiments were done which have given information regarding the intermolecular forces involved in these systems. The pH is crucial ensuring formation of racemic [Tb(DPA = 2,6-pyridine-dicarboxylate)₃]^3-, it also ensures the amino acid remains in its zwitter ionic form. Binary solvent systems with/without the capacity to hydrogen bond have shown hydrogen bonding strength of the solvent system greatly influences how the chiral amino acid perturbs the racemic [Tb(DPA)₃]^3- equilibrium. We have also attempted to parallel the Hofmeister series of salts to investigate the salting in and salting out phenomena seen in proteins.

      In this study we have investigated some factors that affect the differential perturbation of a lanthanide(III) racemic equilibrium by added chiral amino acids. Through these studies it is possible to begin to determine the true nature of the Pfeiffer effect. By understanding these relationships we may also begin to understand the nature of similar interactions that may have biological significance.