An interdiscplinary laboratory project based on insulin gels as models of amyloid plaques

CHED 1162

Robert F. Pasternack1, Esther Gibbs2, and Kathleen E. Kristian1. (1) Department of Chemistry, Swarthmore College, 500 College Avenue, Swarthmore, PA 19081, (2) Department of Chemistry, Goucher College, Towson, MD 21204
Advanced Laboratory in Chemistry and Biochemistry is an integrated lab course offering at Swarthmore College in which students undertake four three-week projects, each supervised by a different faculty member. One of these projects “INSULIN GELATION AND THE FORMATION AND CHARACTERIZATION OF AMYLOID AGGREGATES” could also be incorporated in a physical chemistry course, an instrumental/analytical course, or a biochemistry course. The experiments represent a real world (medical implications), interdisciplinary project that explores autocatalytic kinetics and some fundamentals of macromolecular structure including the formation of supramolecular assemblies. Students have the opportunity to use a number of spectroscopic techniques, limited only by the equipment holdings of the department in question. In the full form of the experiment, all of absorption, fluorescence, light scattering and circular dichroism are employed to study the gelation process. In the course of these experiments students measure turbidity of protein solutions, determine peptide secondary structure, use dyes as indicators of amyloid structure formation, and apply a sophisticated fitting routine for kinetic analysis. The time profile for gelation requires the use of a new, autocatalytic kinetic model for analysis derived in part from a consideration of the fractal dimensions of the aggregate. The experiment is open-ended and allows the student participants to design variations and extensions of the basic protocols. The impact of additives on the kinetics of gelation is one area of interest for further study, as is the effect of temperature and ionic strength.