Fluorescent peptides to investigate amyloid self-assembly using two-photon microscopy

摘要

While the growth and structure of amyloid fibers with β-sheet secondary structure has been widely investigated in recent years, the mechanism of self-assembly remains poorly understood. Multiple intermediate species have been proposed to play important roles in the self assembly process, yet many of these remain poorly defined or have not been clearly observed. Fluorescence microscopy and spectroscopy should provide powerful tools to amyloid formation mechanisms, although given the tight packing of molecules within amyloid structures one must be concerned about the extent to which the coupling of fluorescent probes will interfere with the amyloid formation process. We have performed systematic characterization of the self assembly and interactions between a model amyloid forming peptide, residues 16-22 from the amyloid beta peptide, together with two different rhodamine conjugated forms of this same peptide sequence. We observe that in some cases, the fluorescent dye does appear to alter the morphology of assembled amyloid structures. We also report on amyloid formation using mixtures of labeled and unlabeled peptides which does not perturb the morphology of the amyloid fibers and tubes, and appears to provide an excellent system for further investigation of amyloid formation.