Chemical Probes for Amyloid Oligomers

University Of California-Irvine, Irvine CA

Investigators

Abstract

With this award, the Chemistry of Life Processes program in the Chemistry Division is funding Dr. James Nowick from the University of California Irvine to investigate interactions between a class of dye molecules and small aggregates of peptide molecules that are associated with amyloid diseases, such as Alzheimer's disease. These aggregates, termed "oligomers," are thought to be the damaging species responsible for neurodegeneration associated with the disease. Dyes have long been used as chemical probes to visualize and monitor amyloid fibril formation and recently have proven valuable in imaging to monitor amyloid fibrils in the brain in a non-invasive fashion. Comparable small molecule probes for amyloid oligomers are lacking. Chemical probes for amyloid oligomers offer the promise of monitoring and visualizing amyloid oligomers in vitro, in biological tissues, and in living cells. The current project will lead to a better understanding of the interactions between the dye molecules and the oligomers and will develop the dyes as useful tools with which to study amyloid oligomers. This pursuit will allow graduate students to earn Ph.D. degrees and enter the US work force as skilled scientists and undergraduate students to receive training in research and go to graduate school or enter the work force as a B.S. Chemists. Additional impact will be achieved through the training of high school students and through K-12 outreach. The current project relies on two discoveries in the laboratory of the Principal Investigator. The first discovery is that macrocyclic beta-hairpin peptides derived from the beta-amyloid peptide assemble to form trimers with well-defined three-fold symmetry. The second discovery is that triphenylmethane dyes such as crystal violet bind to the trimers with low-micromolar affinities. The dyes provide a visible response to the oligomers, changing color from violet to blue and becoming fluorescent. These spectral changes in response to amyloid oligomers can also be measured spectrophotometrically or observed in fluorescence microscopy. For these reasons, triphenylmethane dyes offer promise as chemical probes for amyloid oligomers. Two aims will be achieved. The first aim is to better understand the binding of triphenylmethane dyes to trimers of macrocyclic beta-hairpin peptides. This goal will be achieved through structure-activity-relationship studies in which the structures of the trimers and the dyes are modified. The second aim is to develop triphenylmethane dyes as chemical probes for synthetic and biogenic oligomers of the full-length beta-amyloid peptide. One set of studies will focus on developing triphenylmethane dyes bearing photo-reactive functional groups as photoaffinity labels for oligomers of the beta-amyloid peptide. A second set of experiments will focus on developing immobilized triphenylmethane dyes to allow affinity-based purification of beta-amyloid oligomers from tissue. Additional experiments will focus on using triphenylmethane dyes to discover novel ligands for amyloid oligomers. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.