Protein-induced photophysical changes to the amyloid indicator dye thioflavin T

• DOI: 10.1073/pnas.1002867107
• Publication Date: 2010-09-09T02:24:07Z
• Authors: Leslie S. Wolfe; Matthew F. Calabrese; Abhinav Nath; Dorottya V. Blaho; Andrew D. Miranker; Yong Xiong
• Keywords: Thioflavin; Quantum yield; Amyloid (mycology)

The small molecule thioflavin T (ThT) is a defining probe for the identification and mechanistic study of amyloid fiber formation. As such, ThT fundamental to investigations serious diseases such as Alzheimer’s disease, Parkinson type II diabetes. For each different protein undergoes conformational conversion β-sheet rich fiber. fluorescence exhibits an increase in quantum yield upon binding these fibers. Despite its widespread use, structural basis specificity changes photophysical properties remain poorly understood. Here, we report co-crystal structures with two alternative states β-2 microglobulin (β2m); one monomeric, other amyloid-like oligomer. In latter, dye intercalates between β-sheets orthogonal β-strands. Importantly, fluorophore bound manner that photophysically relevant torsion limited range angles generally associated low, not high, yield. Quantum mechanical assessment shows electronic distribution be strongly stabilized by aromatic interactions protein. Monomeric β2m gives little despite showing three fluorophores, at sites, configurations high Our efforts fundamentally extend existing understanding about origins amyloid-induced changes. Specifically, interface characterizes acts both sterically electronically stabilize fluorophore’s ground state distribution. By preventing from adopting preferred excited configuration, nonradiative relaxation pathways are minimized increased.