Abstract
Various structural models for Amyloid $\beta$ fibrils derived from a variety of experimental techniques are currently available. However, this data cannot differentiate between the relative position of the two arms of the $\beta$ hairpin called the stagger. Amyloid fibrils of various heirarchical levels form left--handed helices composed of $\beta$ sheets. However it is unclear if positive, negative and neutral staggers all form the macroscopic left--handed helices. Studying this is important since the success of computational approaches to develop drugs for amyloidic diseases will depend on selecting the physiologically relevant structure of the sheets. To address this issue we have conducted extensive molecular dynamics simulations of Amyloid$\beta$ sheets of various staggers and show that only negative staggers generate the experimentally observed left--handed helices while positive staggers generate the incorrect right--handed helices. The implications of this result extend in to all amyloidic--aggregation type diseases.