Aggregation of Aβ(1-42) in the presence of short peptides: conformational studies

CD and infrared spectroscopic studies were performed on (i) the inhibitory effects of equimolar quantities of LPFFD‐OH and LPYFD‐NH2 on the time‐dependent aggregation of amyloid β‐protein (Aβ) (1–42) and (ii) the β‐sheet‐breaker effects of two‐fold molar excess of the pentapeptides on aggregated Aβ(1–42) aged 1 week. The data obtained from the time‐dependent studies demonstrated that LPFFD‐OH did not significantly influence, whereas LPYFD‐NH2 exerted some inhibitory effect on the aggregation of Aβ(1–42). When added to a solution of Aβ(1–42) aged 1 week, LPFFD‐OH accelerated, while LPYFD‐NH2 delayed, but did not prevent further fibrillogenesis. The difference in the effects of these two pentapeptides on the aggregational profile of Aβ(1–42) is probably due to the difference in their conformational preferences: LPFFD‐OH adopts a β‐turn and extended structures, while LPYFD‐NH2 adopts a prevailing β‐turn conformation. Copyright © 2008 European Peptide Society and John Wiley & Sons, Ltd.