Direct Detection of XXXX Dimerization Dynamics: Single-Molecule Fluorescence Analysis.

@entity34716 @entity15735 @entity8095 @entity1423 @entity20097 @entity191 @entity20098
The aggregation of @entity8095 (a- @entity15735 ) is linked to @entity191 . The mechanism of @entity1423 steps and the effect of pathogenic single-point mutations remain elusive. We report here a single-molecule fluorescence study of a- @entity15735 dimerization and the effect of mutations. Specific interactions between tethered fluorophore-free a- @entity15735 monomers on a substrate and fluorophore-labeled monomers diffusing freely in solution were observed using total internal reflection fluorescence microscopy. The results showed that wild-type (WT) a- @entity15735 dimers adopt two types of dimers. The lifetimes of type 1 and type 2 dimers were determined to be 197    3  ms and 3334    145  ms, respectively. All three of the mutations used, @entity20097 , @entity34716 , and @entity20098 , increased the lifetime of type 1 dimer and enhanced the relative population of type 2 dimer, with type 1 dimer constituting the major fraction. The kinetic stability of type 1 dimers (expressed in terms of lifetime) followed the order @entity20097 (693    14  ms) > @entity34716 (292    5  ms) > @entity20098 (226    6  ms) > WT (197    3  ms). Type 2 dimers, which are more stable, had lifetimes in the range of several seconds. The strongest effect, observed for the @entity20097 mutant, resulted in a lifetime 3.5 times higher than observed for the WT type 1 dimer. This mutation also doubled the relative fraction of type 2 dimer. These data show that single-point mutations promote dimerization, and they suggest that the structural heterogeneity of a- @entity15735 dimers could lead to different aggregation pathways.
