Investigação dos sítios de interação entre as cadeias peptídicas do beta-amiloide usando as propriedades fotoquímicas e fotofísicas do complexo luminescente cis-[Ru(phen)2(Aepy)2]2+

Abstract

Alzheimer’s disease (AD) is a progressive neurodegenerative disorder associated with the aggregation of amyloid-β peptide (Aβ) into species ranging from soluble oligomers to amyloid fibrils and plaques. Understanding the molecular interactions involved in this process is important for identifying peptide regions associated with aggregate formation and stabilization. In this context, Ru(II) polypyridyl complexes exhibit photophysical and photochemical properties that make them useful molecular tools for investigating amyloid aggregation. In this work, the luminescent RuAepy complex was investigated with emphasis on its interaction with Aβ and the identification of peptide regions involved in this process. The complex was synthesized and characterized by spectroscopic and spectrometric techniques, and its photophysical and photochemical properties were evaluated in solution. Its interaction with Aβ was investigated using Aβ₁₋₄₀, Aβ₁₋₄2 and peptide fragments by luminescence spectroscopy and 1H nuclear magnetic resonance (1H NMR). Luminescence studies revealed changes in the intrinsic emission of Tyr10 in the presence of RuAepy, indicating modifications in its local microenvironment. The in situ and ex situ experiments showed that RuAepy affects Aβ species and modifies its aggregation behavior. Studies using peptide fragments, combined with 1H NMR analyses, indicated the involvement of the N-terminal region, particularly His6, in the interaction with the complex. Overall, the results demonstrate that RuAepy interacts with Aβ and modifies its aggregation process, supporting the use of Ru(II) polypyridyl complexes as molecular tools for investigating the interactions involved in amyloid aggregate formation.