Example III (cont.): In Situ Tapping Mode AFM Study of Peptides Involved in Alzheimer’s Disease (AD).  Introduction: Beta amyloid

b - amyloid is produced in the process of cleavage of membrane protein referred to as amyloid precursor protein

normal enzymatic processing

abnormal enzymatic processing

b - amyloid (Ab)

D. Selkoe,  Scientific American, 1991

Due to its origin as a trans-membrane fragment, Ab is highly amphipathic.  The hydrophobic part, which resided in the interior of the membrane, drives soluble Ab towards aggregation. The aggregated form is fibrillar and is rich in b-sheets.