Tracking Internal and Global Diffusive Dynamics During Protein Aggregation by High-Resolution Neutron Spectroscopy

Abstract

Proteins can misfold and form either amorphous or organized aggregates with different morphologies and features. Aggregates of amyloid nature are pathological hallmarks in so-called protein conformational diseases, including Alzheimer’s and Parkinson’s. Evidence prevails that the transient early phases of the reaction determine the aggregate morphology and toxicity. As a consequence, real-time monitoring of protein aggregation is of utmost importance. Here, we employed time-resolved neutron backscattering spectroscopy to follow center-of-mass self-diffusion and nano- to picosecond internal dynamics of lysozyme during aggregation into a specific β-sheet rich superstructure, called particulates, formed at the isoelectric point of the protein. Particulate formation is found to be a one-step process, and protein internal dynamics, to remain unchanged during the entire aggregation process. The time-resolved neutron backscattering spectroscopy approach developed here, in combination with standard kinetics assays, provides a unifying framework in which dynamics and conformational transitions can be related to the different aggregation pathways.

Ion-Mediated Morphological Diversity in Protein Amyloid Systems

“…For sulfate, microparticles are observed already at low ionic strengths for both proteins (Figures S7–S9 and S21–S23). As shown in previous studies, the formation of microparticles is likely the result of a rapid aggregation supporting the hypothesis that colloidal stability rather than the folding stability of the single molecule rules the aggregation process − (Figure c). In contrast, the formation of fibrils and spherulites is controlled by the conformational stability of the single protein. , The latter process requires a substantial unfolding of the protein molecule structure and the appearance of preaggregate intermediate states, following a nucleation–elongation reaction (Figure d).…”

Zinc determines dynamical properties and aggregation kinetics of human insulin

“…These results are in contrast with our previous results on tau protein (52) , where no differences between native-state and fibril dynamics were observed on the same timescale, and on concanavalin A, where internal dynamics were found to be larger in the amyloid than in the native species (51) . The tau results were suggestive of the protein internal energy depending only on the amino acid composition (87) and not on the structure or aggregation state, as also supported by solution studies showing that the internal dynamics remain unchanged upon denaturation (88) and upon aggregation (89) .…”

Effects of heavy water on protein dynamics studied by molecular dynamics simulation: Focusing on dynamical parameters obtained by quasi-elastic neutron scattering

“…Recent QENS measurements on protein samples are often carried out at the energy resolutions of higher than 15 μeV (e.g. [38][39][40]). In these conditions, as seen in Fig.…”