Investigating the Interactions of Ions with Polypeptides

With support from the Macromolecular, Supramolecular, and Nanochemistry program of the Chemistry Division, Professor Paul S. Cremer at the Pennsylvania State University is exploring the roles that ions play in aqueous solutions containing organic molecules and polymers. Such research can have broad impact as ions influence an enormous variety of processes from allowing molecules to clump together or aggregate, to catalyze processes in cells, and even the length of time it takes to pickle a cucumber. Understanding the pathways that enable proteins to aggregate into particular structures may help reveal the nature of certain human diseases. The behavior of the solutions will be used to create simple demonstration devices as part of an educational outreach effort.

Cations and anions in aqueous solvent may interact with each other or with charged groups on small molecules, Langmuir monolayers, and polymer chains. A variety of spectroscopies including infrared, Raman, and vibrational sum frequency generation will be used to investigate how contact pair, solvent shared, and solvent separated ion-ion interactions are affected by the size of the ions, their geometry, their hydrogen bonding ability, van der Waals forces, and the surrounding chemical environment. The molecular level details of these interactions will then be correlated with thermodynamic properties of the corresponding aqueous solutions to understand how ion pairing can influence macroscopic behavior.