A Comprehensive Analysis of the Intrinsic Visible Fluorescence Emitted by Peptide/Protein Amyloid-like Assemblies

Abstract

Amyloid aggregation is a widespread process that involves proteins and peptides with different molecular complexity and amino acid composition. The structural motif (cross-β) underlying this supramolecular organization generates aggregates endowed with special mechanical and spectroscopic properties with huge implications in biomedical and technological fields, including emerging precision medicine. The puzzling ability of these assemblies to emit intrinsic and label-free fluorescence in regions of the electromagnetic spectrum, such as visible and even infrared, usually considered to be forbidden in the polypeptide chain, has attracted interest for its many implications in both basic and applied science. Despite the interest in this phenomenon, the physical basis of its origin is still poorly understood. To gain a global view of the available information on this phenomenon, we here provide an exhaustive survey of the current literature in which original data on this fluorescence have been reported. The emitting systems have been classified in terms of their molecular complexity, amino acid composition, and physical state. Information about the wavelength of the radiation used for the excitation as well as the emission range/peak has also been retrieved. The data collected here provide a picture of the complexity of this multifaceted phenomenon that could be helpful for future studies aimed at defining its structural and electronic basis and/or stimulating new applications.

A Diruthenium Metallodrug as a Potent Inhibitor of Amyloid-β Aggregation: Synergism of Mechanisms of Action

“…The change of intrinsic fluorescence of Aβ peptides offers valuable information about the structure, folding, and dynamic of these molecules. The effect of complexes 1 and 2 on the autofluorescence of amyloid aggregates formation was evaluated by recording fluorescence emission spectra over time (Figure ). The native Aβ 1–42 exhibits a time dependent increase of emission intensities with maxima centered at two different wavelengths: 478 and 517 nm, respectively .…”

Comparative Analysis of the Inhibitory Mechanism of Aβ1–42 Aggregation by Diruthenium Complexes

“…The autofluorescence assay of amyloid systems is becoming a valuable tool to evaluate the modulatory effects of chemical agents during aggregation. 40 The effects of Ru 2 complexes on the autofluorescence of the Aβ 1−42 peptide were evaluated by recording fluorescence emission spectra over time at different excitation wavelengths in the absence and presence of the diruthenium complexes (Figure 2). As anticipated, excitation at 390 nm results in an increase of emission intensity at 478 nm after 48 h (Figure 2a).…”

Self-Assembled Materials Based on Fully Aromatic Peptides: The Impact of Tryptophan, Tyrosine, and Dopa Residues

“…MD studies demonstrated that the interconnected fibrillary networks are originated by the capability of these peptides to opportunely arrange by forming two interfaces: a wet and a dry one. In the attempt to identify novel materials with enhanced and unexpected properties, we punctually replaced the original, natural amino acids with the non-natural ones like Nal and Dopa . The effect of these modifications and of the PEG moiety at the N-terminus of the peptides were evaluated. , …”