The three-dimensional solution structure of Aß (1-28) reveals the folding of the peptide to form a predominantly a-helical structure with a bend centered at residue 12 and the side chains of histidine-13 and lysine-16 in close proximity, residing on the same face of the helix. Their proximity may constitute a binding motif with the heparan sulfate proteoglycans. Aß (1-28) is highly hydrophilic and shares sequences with bA4, the major component of Aß. Its assembly is fibrillar, i.e., elongated in a single direction. Reports show that synthetic peptides Aß (1-40) and Aß (1-28) have significant effects on normal human plasma cholesterol esterification rate. Both peptides (at concentration of 1 ng/mL) inhibit plasma cholesterol esterification rate by 40-50% compared to the control value.