Spectroscopic Investigations of β-Amyloid Interactions with Propofol and L-Arginine

Abstract

Beta amyloid (Aβ) aggregation has been characterized to be responsible for several amyloid diseases. Fourier transform infrared (FTIR) spectroscopy, fluorescence, and atomic force microscopy (AFM) are used to investigate induced changes in the secondary structure of Aβ upon thermal denaturation and interaction with propofol and L-arginine. Spectral analysis has revealed an effective static quenching for the intrinsic fluorescence of Aβ by propofol and l-arginine with binding constants of 2.81 × 102 M−1 for Aβ-propofol and 0.37 × 102 M−1 for Aβ-L-arginine. Fourier self-deconvolution (FSD) technique has been used to evaluate the relative intensity changes in the spectra of the component bands in the amide I and amide II regions at different ligand’s concentration in the protein complex. The analysis showed a decrease in the intensities of the parallel beta bands of propofol and L-arginine interactions with Aβ, accompanied with an increase in the antiparallel bands for the Aβ-propofol interaction and a decrease for the Aβ-l-arginine interaction. The relative increase in peaks’ intensities at 1694 cm−1 and 1531 cm−1 for the propofol interaction is linked to the formation of oligomers in the protein.