A Spectroscopic Marker for Structural Transitions Associated with Amyloid-β Aggregation

Area of Science:

• Biochemistry
• Neuroscience
• Materials Science

Background:

• Amyloid aggregates, implicated in diseases like Alzheimer's, form through various intermediates with distinct structures and toxicities.
• Early oligomeric amyloid-beta (Aβ) species are highly cytotoxic but challenging to identify due to their transient nature.
• Conventional methods like thioflavin T lack specificity in differentiating Aβ aggregation stages.

Purpose of the Study:

• To introduce a novel fluorescent dye, bis(triphenylphosphonium) tetraphenylethene (TPE-TPP), for identifying and characterizing Aβ aggregation intermediates.
• To demonstrate the capability of TPE-TPP to differentiate between various Aβ aggregate species based on their fluorescence properties.
• To explore the potential of TPE-TPP as a diagnostic tool for amyloid aggregation and inhibitor screening.

Main Methods:

• Utilized the fluorescent dye TPE-TPP to monitor amyloid-beta (Aβ) aggregation.
• Analyzed steady state fluorescence and fluorescence lifetime characteristics of TPE-TPP in the presence of different Aβ species.
• Correlated TPE-TPP fluorescence data with known structural features of Aβ intermediates from solid-state NMR spectroscopy.

Main Results:

• TPE-TPP identified at least three distinct Aβ aggregation intermediates.
• Distinct fluorescence signatures (emission maxima and lifetimes) were observed for small oligomers, intermediate species, and fibrils.
• Small oligomers: λmax = 465 nm, τFl = 3.58 ± 0.04 ns; Intermediates: λmax = 452 nm, τFl = 3.00 ± 0.03 ns; Fibrils: λmax = 406 nm, τFl = 5.19 ± 0.08 ns.

Conclusions:

• TPE-TPP serves as a sensitive probe for distinguishing between different amyloid-beta (Aβ) aggregation states.
• This fluorescence-based method provides a valuable diagnostic tool for studying toxic Aβ aggregates.
• TPE-TPP holds promise for screening compounds that inhibit amyloid aggregation, potentially aiding in Alzheimer's disease research.