Nanoscale Assembly of Proteins into Amyloid Oligomers, Pores and Fibrils

Abstract

Protein amyloid aggregates are implicated in a variety of debilitating human disorders such as Alzheimer's, Parkinson's and prion diseases. The transition from a normal functional protein to an abnormal misfolded form involves a profound conformational change that serves as the key step in amyloid assembly leading to nanoscopic oligomers, pores and fibrils. Using Raman spectroscopy in combination with atomic force microscopy (Figure 1a,b), we have been able to delineate the key structural transitions during amyloid formation (Bhattacharya et al. J. Phys. Chem. Lett. 2013,4, 480-485). Moreover, the underlying molecular mechanism by which amyloids are involved in inducing cellular toxicity remains elusive because the conventional optical microscopy does not allow one to monitor these processes directly at a high spatial resolution due to the diffraction-limit. Using near-field scanning fluorescence microscopy, we have been able to image the fibrils far beyond the diffraction-limit and interrogate individual fibrils by simultaneously monitoring both nanoscale topography and fluorescence brightness along the length of the fibrils (Figure 1c,d). Our nanoscale imaging results provide structural underpinnings of the supramolecular packing within the nanoscopic amyloids (Dalal & Bhattacharya et al. J. Phys. Chem. Lett. 2012, 3, 1783-1787).View Large Image | View Hi-Res Image | Download PowerPoint Slide