Direct characterization of amyloidogenic oligomers by single-molecule fluorescence

Angel Orte, Neil R Birkett, Richard W Clarke, Glyn Lee Devlin, Christopher M Dobson, David Klenerman

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155 Citations (Scopus)


A key issue in understanding the pathogenic conditions associated with the aberrant aggregation of misfolded proteins is the identification and characterization of species formed during the aggregation process. Probing the nature of such species has, however, proved to be extremely challenging to conventional techniques because of their transient and heterogeneous character. We describe here the application of a two-color single-molecule fluorescence technique to examine the assembly of oligomeric species formed during the aggregation of the SH3 domain of PI3 kinase. The single-molecule experiments show that the species formed at the stage of the reaction where aggregates have previously been found to be maximally cytotoxic are a heterogeneous ensemble of oligomers with a median size of 38 ? 10 molecules. This number is remarkably similar to estimates from bulk measurements of the critical size of species observed to seed ordered fibril formation and of the most infective form of prion particles. Moreover, although the size distribution of the SH3 oligomers remains virtually constant as the time of aggregation increases, their stability increases substantially. These findings together provide direct evidence for a general mechanism of amyloid aggregation in which the stable cross-a structure emerges via internal reorganization of disordered oligomers formed during the lag phase of the self-assembly reaction.
Original languageEnglish
Pages (from-to)14424 - 14429
Number of pages6
JournalProceedings of the National Academy of Sciences of the United States of America
Issue number38
Publication statusPublished - 2008
Externally publishedYes

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