Evaluation of Peptide/Protein Self-Assembly and Aggregation by Spectroscopic Methods

Abstract

The self-assembly of proteins is an essential process for a variety of cellular functions including cell respiration, mobility and division. On the other hand, protein or peptide misfolding and aggregation is related to the development of Parkinson’s disease and Alzheimer’s disease, among other aggregopathies. As a consequence, significant research efforts are directed towards the understanding of this process. In this review, we are focused on the use of UV-Visible Absorption Spectroscopy, Fluorescence Spectroscopy and Circular Dichroism to evaluate the self-organization of proteins and peptides in solution. These spectroscopic techniques are commonly available in most chemistry and biochemistry research laboratories, and together they are a powerful approach for initial as well as routine evaluation of protein and peptide self-assembly and aggregation under different environmental stimulus. Furthermore, these spectroscopic techniques are even suitable for studying complex systems like those in the food industry or pharmaceutical formulations, providing an overall idea of the folding, self-assembly, and aggregation processes, which is challenging to obtain with high-resolution methods. Here, we compiled and discussed selected examples, together with our results and those that helped us better to understand the process of protein and peptide aggregation. We put particular emphasis on the basic description of the methods as well as on the experimental considerations needed to obtain meaningful information, to help those who are just getting into this exciting area of research. Moreover, this review is particularly useful to those out of the field who would like to improve reproducibility in their cellular and biomedical experiments, especially while working with peptide and protein systems as an external stimulus. Our final aim is to show the power of these low-resolution techniques to improve our understanding of the self-assembly of peptides and proteins and translate this fundamental knowledge in biomedical research or food applications.

Enhanced Stability of Detergent-Free Human Native STEAP1 Protein from Neoplastic Prostate Cancer Cells upon an Innovative Isolation Procedure

“…This typical CD signature revealed for the first time that the native human STEAP1 predominantly adopts an α-helical structure [ 60 , 61 ]. The slight wavelength shift of the maximum value when compared to typical absorbances for α-helix structures (193 nm), was attributed to the large hydrophobic nature of STEAP1 and the environment wherein the protein of interest is sequestered [ 60 , 61 ].…”

“…This typical CD signature revealed for the first time that the native human STEAP1 predominantly adopts an α-helical structure [ 60 , 61 ]. The slight wavelength shift of the maximum value when compared to typical absorbances for α-helix structures (193 nm), was attributed to the large hydrophobic nature of STEAP1 and the environment wherein the protein of interest is sequestered [ 60 , 61 ]. This finding is in full concordance with the predicted α-helical transmembrane arrangement cryo-EM structure of trimeric human STEAP1 bound to three Fab fragments, already deposited in the PDB [ 5 ].…”

Capacity for increased surface area in the hydrophobic core of β‐sheet peptide bilayer nanoribbons

“…UV spectra were also collected for the molecular assemblies of each peptide derivative (Figure S29). The nanoribbons had absorption signals between 250 and 300 nm consistent with presence of the aromatic amino acids, with Ac‐(HphKHphE) 2 ‐NH 2 and Ac‐WKFEFKFE‐NH 2 exhibiting the weakest absorbance in this range 45,46 . The mono‐substituted, di‐substituted, and fully substituted Bip derivatives had an overlaying peak at 250 nm.…”

“…The nanoribbons had absorption signals between 250 and 300 nm consistent with presence of the aromatic amino acids, with Ac‐(HphKHphE) 2 ‐NH 2 and Ac‐WKFEFKFE‐NH 2 exhibiting the weakest absorbance in this range. 45 , 46 The mono‐substituted, di‐substituted, and fully substituted Bip derivatives had an overlaying peak at 250 nm. We also observed a long tail over 600 nm that is consistent with elongated π‐stacking or scattering effects from large molecular assemblies.…”

Selected Spectroscopic Techniques for Surface Analysis of Dental Materials: A Narrative Review

“…Depending on the radiation range, different radiation sources, detectors and dispersion devices are used. In optical spectroscopy, prisms and diffraction gratings are most frequently used as dispersion devices [ 54 , 55 , 56 , 57 ].…”