title: Heterogeneity and Turnover of Intermediates during Amyloid-β (Aβ) Peptide Aggregation Studied by Fluorescence Correlation Spectroscopy.
abstract: Self-assembly of amyloid β (Aβ) peptide molecules into large aggregates is a naturally occurring process driven in aqueous solution by a dynamic interplay between hydrophobic interactions among Aβ molecules, which promote aggregation, and steric and overall electrostatic hindrance, which stifles it. Aβ self-association is entropically unfavorable, as it implies order increase in the system, but under favorable kinetic conditions, the process proceeds at appreciable rates, yielding Aβ aggregates of different sizes and structures. Despite the great relevance and extensive research efforts, detailed kinetic mechanisms underlying Aβ aggregation remain only partially understood. In this study, fluorescence correlation spectroscopy (FCS) and Thioflavin T (ThT) were used to monitor the time dependent growth of structured aggregates and characterize multiple components during the aggregation of Aβ peptides in a heterogeneous aqueous solution. To this aim, we collected data during a relatively large number of observation periods, 30 consecutive measurements lasting 10 s each, at what we consider to be a constant time point in the slow aggregation process. This approach enabled monitoring the formation of nanomolar concentrations of structured amyloid aggregates and demonstrated the changing distribution of amyloid aggregate sizes throughout the aggregation process. We identified aggregates of different sizes with molecular weight from 260 to more than 1 × 10(6) kDa and revealed the hitherto unobserved kinetic turnover of intermediates during Aβ aggregation. The effect of different Aβ concentrations, Aβ:ThT ratios, differences between the 40 (Aβ40) and 42 (Aβ42) residue long variants of Aβ, and the effect of stirring were also examined.
authors.affiliation: Department of Biochemistry and Biophysics, Arrhenius Laboratories, Stockholm University , 10691 Stockholm, Sweden.
authors.forename: Ann
authors.initials: A
authors.lastname: Tiiman
authors.affiliation: Department of Biochemistry and Biophysics, Arrhenius Laboratories, Stockholm University , 10691 Stockholm, Sweden.|The National Institute of Chemical Physics and Biophysics , Akadeemia tee 23, 12618 Tallinn, Estonia.
authors.forename: Jüri
authors.initials: J
authors.lastname: Jarvet
authors.affiliation: Department of Biochemistry and Biophysics, Arrhenius Laboratories, Stockholm University , 10691 Stockholm, Sweden.
authors.forename: Astrid
authors.initials: A
authors.lastname: Gräslund
authors.affiliation: Department of Clinical Neuroscience, Center for Molecular Medicine CMM L8:01, Karolinska Institutet , 17176 Stockholm, Sweden.
authors.forename: Vladana
authors.initials: V
authors.lastname: Vukojević
mesh_terms: D016229:Amyloid beta-Peptides / Q000737:chemistry*; D052160:Benzothiazoles; D006801:Humans; D010446:Peptide Fragments / Q000737:chemistry*; D066329:Protein Aggregates; D013050:Spectrometry, Fluorescence; D013844:Thiazoles / Q000737:chemistry*
chemical_list: D016229:Amyloid beta-Peptides; D052160:Benzothiazoles; D010446:Peptide Fragments; D066329:Protein Aggregates; D013844:Thiazoles; C078592:amyloid beta-protein (1-40); C075222:amyloid beta-protein (1-42); C009462:thioflavin T