High pressure FT-IR spectroscopic study on the secondary structure changes in insulin amyloid fibril and aggregate

Abstract

The pressure-induced changes in the secondary structure of two kinds of insulin aggregates, amyloid fibril and reduction-induced aggregate, were studied by using Fourier transform infrared (FT-IR) spectroscopy. The parallel β-sheet for the amyloid fibril is not unfolded, but dramatically distorted with increasing pressure up to 1.0 GPa. This structural rearrangement is elastic and does not cause the backbone amide protons involved in the parallel β-sheet to expose to an aqueous medium. The dissociation of the amyloid fibril into its monomer or oligomer is not likely to be promoted by application of high pressure. The antiparallel β -sheet of the reduction-induced aggregate remains distinct at 1.3 GPa. The whole construction is quite rigid in spite of the fact that the same origin (i.e. insulin) as the amyloid fibril is formed.

Keywords:

• FT-IR spectroscopy
• secondary structure
• insulin
• amyloid fibril
• aggregate