Circular dichroism (CD) spectroscopy of proteins/peptides in thin films can provide valuable information on the structures in the aggregated states; however, it is difficult to estimate the secondary structure content quantitatively due to artifact signals arising from macroscopic anisotropies which is unique to the solid phase. Using a Universal Chiroptical Spectrophotometer (UCS-1) together with the measurement and analytical procedures we have developed, we could obtain artifact-free CD spectra of cast and Langmuir-Blodgett (L-B) films of synthetic peptides, Aβ (1-40) and (1-42) which are related to Alzheimer's disease. The work gave insights into the mechanisms for structural transformation and amyloid-like aggregation.
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