Abstract
The interfacial behavior of the model amyloid peptide octamer YYKLVFFC (peptide 1) and two other amyloid peptides YEVHHQKLVFF (peptide 2) and KKLVFFA (peptide 3) at the metal|aqueous solution interface was studied by voltammetric and constant current chronopotentiometric stripping (CPS). All three peptides are adsorbed in a wide potential range and exhibit different interfacial organizations depending on the electrode potential. At the least negative potentials, chemisorption of peptide 1 occurs through the formation of a metalsulfur bond. This bond is broken close to −0.6V. The peptide undergoes self-association at more negative potentials, leading to the formation of a “pit” characteristic of a 2D condensed film. Under the same conditions the other peptides do not produce such a pit. Formation of the 2D condensed layer in peptide 1 is supported by the time, potential and temperature dependences of the interfacial capacity and it is shown that presence of the 2D layer is reflected by the peptide CPS signals due to the catalytic hydrogen evolution. The ability of peptide 1 to form the potential-dependent 2D condensed layer has been reported neither for any other peptide nor for any protein molecule. This ability might be related to the well-known oligomerization and aggregation of Alzheimer amyloid peptides.
Highlights
IntroductionSpecial attention has been paid to diseases in which amyloidogenic proteins, when disturbed from their native state, can form oligomeric and polymeric aggregates [1,2]
Among human neurodegenerative diseases, special attention has been paid to diseases in which amyloidogenic proteins, when disturbed from their native state, can form oligomeric and polymeric aggregates [1,2]
On the PGE, peaks due to Tyr were clearly evidenced by differential pulse voltammetry (DPV) for peptide 1 at +0.51 V and for peptide 2 at +0.53 V while no oxidation peak appeared for peptide 3 not containing Tyr, in agreement with data earlier obtained with peptides [22] and proteins [23] and in studies of a-synuclein oligomerisation and aggregation [4,6,8] and of A-peptide aggregation [5,7,20]
Summary
Special attention has been paid to diseases in which amyloidogenic proteins, when disturbed from their native state, can form oligomeric and polymeric aggregates [1,2]. Such aggregated proteins frequently have a well-defined fibrillar nature termed amyloid. The amyloid peptides (A) in Alzheimer’s disease (AD) can serve as a paradigm for studies of amyloid formation and conformation [1,3] These peptides derive from cleavage of the transmembrane amyloid precursor protein by secretases.
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