title: Heat of supersaturation-limited amyloid burst directly monitored by isothermal titration calorimetry.
abstract: Amyloid fibrils form in supersaturated solutions via a nucleation and growth mechanism. Although the structural features of amyloid fibrils have become increasingly clearer, knowledge on the thermodynamics of fibrillation is limited. Furthermore, protein aggregation is not a target of calorimetry, one of the most powerful approaches used to study proteins. Here, with β2-microglobulin, a protein responsible for dialysis-related amyloidosis, we show direct heat measurements of the formation of amyloid fibrils using isothermal titration calorimetry (ITC). The spontaneous fibrillation after a lag phase was accompanied by exothermic heat. The thermodynamic parameters of fibrillation obtained under various protein concentrations and temperatures were consistent with the main-chain dominated structural model of fibrils, in which overall packing was less than that of the native structures. We also characterized the thermodynamics of amorphous aggregation, enabling the comparison of protein folding, amyloid fibrillation, and amorphous aggregation. These results indicate that ITC will become a promising approach for clarifying comprehensively the thermodynamics of protein folding and misfolding.
authors.affiliation: Division of Protein Structural Biology, Institute for Protein Research, Osaka University, Osaka 565-0871, Japan.
authors.forename: Tatsuya
authors.initials: T
authors.lastname: Ikenoue
authors.forename: Young-Ho
authors.initials: YH
authors.lastname: Lee
authors.forename: József
authors.initials: J
authors.lastname: Kardos
authors.forename: Hisashi
authors.initials: H
authors.lastname: Yagi
authors.forename: Takahisa
authors.initials: T
authors.lastname: Ikegami
authors.forename: Hironobu
authors.initials: H
authors.lastname: Naiki
authors.forename: Yuji
authors.initials: Y
authors.lastname: Goto
mesh_terms: D000682:Amyloid / Q000737:chemistry* / Q000648:ultrastructure; D000686:Amyloidosis / Q000378:metabolism; D002151:Calorimetry; D006358:Hot Temperature; D006801:Humans; D018625:Microscopy, Atomic Force; D017510:Protein Folding; D055550:Protein Stability; D020836:Protein Structure, Quaternary; D011994:Recombinant Proteins / Q000737:chemistry; D012996:Solutions; D013816:Thermodynamics; D001613:beta 2-Microglobulin / Q000737:chemistry* / Q000648:ultrastructure
chemical_list: D000682:Amyloid; D011994:Recombinant Proteins; D012996:Solutions; D001613:beta 2-Microglobulin
keywords: enthalpy change; metastability; solubility; thermodynamic stability; thioflavin T
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