Towards Scaffolds for Rational Self Assembly: Investigating Nucleation Dependent Growth and Self-Healing of Co-Assembled Amyloid Nanotubes

Emory University, Atlanta GA

Investigators

Abstract

ID: MPS/DMR/BMAT(7623) 0907435 PI: Berland, Keith ORG: Emory University Title: Towards Scaffolds for Rational Self Assembly: Investigating Nucleation Dependent Growth and Self-Healing of Co-Assembled Amyloid Nanotubes INTELLECTUAL MERIT: The PIs have observed that prior to ordered assembly, the amyloid forming peptides aggregate into several-micron sized aggregates with morphology that is distinct from the ordered fibers or nanotubes, and that the growth appears to originate from structural reorganization of peptide conformations and interactions within these aggregate structures. These preliminary data represent the first direct observation of amyloid nucleation, and working towards a deeper understanding of the physical mechanisms governing nucleation, growth, and self-healing properties of these nanomaterials is essential for advancing their potential use as functional, rationally-designed platforms for molecular self-assembly. A model system has been developed in which fluorescent peptides are incorporated into the highly ordered assemblies, and these constructs provide a unique opportunity to deepen understanding of the fundamental pathways for assembly. By combining this well defined and structurally characterized model system with state-of-the-art fluorescence microscopy, the research plan has the capability to dramatically advance understanding of these materials. Specifically, it is proposed to apply fluorescence imaging, lifetime imaging, fluctuation spectroscopy, and photobleaching measurements to define amyloid nucleation, elongation and growth as well as the self-healing properties of amyloid nanotubes. The focus will be: Aim 1: Amyloid nucleation. Characterize aggregate structures, structural changes, and associated kinetics involved in amyloid nucleation. These measurements will exploit the experimental model system which has uncovered the first direct observation of amyloid nucleation. Aim 2: Nanotube elongation and growth. Directly observe elongation kinetics and make quantitative measurements of single assembly growth rates to better characterize propagation processes. These measurements can determine whether growth is uni- or bidirectional, and coupled with lifetime microscopy can determine whether mature structures are directly assembled or result from relaxation processes following initial assembly. Aim 3: Peptide exchange and self healing of amyloid structures. Useful nanoscale biomaterials require self-healing capabilities, by which damaged regions can reassemble or self-repair. Initial evidence suggests amyloid structures possess this capability. This aim focuses on detailed experiments that are required to understand the self-repair mechanisms. BROADER IMPACTS: The proposed studies represent a collaborative effort of the Berland (Department of Physics) and Lynn (Department of Chemistry) labs at Emory University. The interdisciplinary nature of the research provides the opportunity for new training opportunities, both within the Emory community and beyond. A strength of the teaching and research collaboration is that the students are trained in the physical spectroscopy, chemical synthesis, and the analysis techniques necessary to work on interdisciplinary research topics. The co-PI organizes a series of freshman seminar courses called ?Origins of ORDER? (On Recent Discoveries by Emory Researchers) that introduce undergraduate students to cutting edge research. The PI and a recent postdoctoral associate have developed materials for this course, which were used to teach freshmen about fluorescence and fluctuations, and their applications in modern research. Both PIs for this proposal have a history of supervising undergraduate research projects, providing academic year and summer student training each year. Beyond the Emory community both PIs have also used the research laboratory to share enthusiasm and excitement for scientific research with those outside the University, including interacting with researchers from other institutions as well as high school students and high school teachers.