Fluorescence anisotropy: a method for early detection of Alzheimer beta-peptide (Abeta) aggregation.

Time-resolved anisotropy measurements (TRAMS) have been used to study the aggregation of the beta-amyloid (Abeta) peptide which is suspected of playing a central role in the pathogenesis of Alzheimer's Disease (AD). The experiments, which employ small quantities of fluorescently-labelled Abeta, in addition to the untagged peptide, have shown that the sensitive TRAMS technique detects the presence of preformed "seed" particles in freshly prepared solutions of Abeta. More importantly, as 100 microM solutions of Abeta containing tagged Abeta at a concentration level of either 0.5 or 1 microM are incubated, the TRAMS prove capable of detection of the peptide aggregation process through the appearance of a continuously increasing "residual anisotropy" within the time-resolved fluorescence data. The method detects Abeta aggregation in its earliest stages, well before complexation becomes apparent in more conventional methods such as the thioflavin T fluorescence assay. The TRAMS approach promises to provide a most attractive route for establishment of a high-throughput procedure for the early detection of the presence of amyloid aggregates in the screening of biological samples.