A two-dimensional approach to study amyloid β-peptide fragment (25-35)

The neuritic plaques formed by amyloid beta-peptide (A beta) play a seminal role in the pathogenesis of Alzheimer's disease (AD). A beta sequence 25-35 (GSNKGAIIGLM) is among the most frequently studied A beta derivatives for the reason that it possesses the structural characteristic of A beta and remains neurotoxic. A beta(25-35) was modified with an aliphatic chain (C-18) at the N-terminal of the peptide for the study of the Langmuir monolayer at the air-water interface. The main advantage of the 2D approach is the self-assembly of the peptide moiety in the subphase, and therefore the aggregation process of the peptidolipid A beta(25-35) was monitored by surface pressure and surface potential-area isotherms. The real-time epifluorescence microscopy was utilized to observe the topography of the domains formed, whereas polarization modulation infrared reflection absorption spectroscopy (PM-IRRAS) provided the information on the structural features of the domains at the air-water interface. Langmuir-Blodgett films were prepared to examine by circular dichroism (CD) the conformation of the peptidolipid film in the domains.