Interaction studies of luminescent conjugated oligothiophenes with aggregated Amyloid β

Abstract: Alzheimer’s disease is the most common cause of dementia and was responsible for over 2% of all deaths in Sweden 2012. One of the pathological hallmarks is amyloid plaques built by fibrillated Amyloid β. Luminescent conjugated oligothiophenes are known to stain and give characteristic fluorescence spectra when staining amyloid fibrils. Little is however known about the interactions between LCOs and fibrils. Studies have been performed on molecules more traditionally known to stain amyloid fibrils. Studies have also been performed on fibrils using limited proteolysis. So far no studies have been performed using LCOs combined with limited proteolysis in order to study the interaction pattern between LCOs and fibrils. Amyloid β is expressed and purified using a simple few step purification protocol. The amyloid β peptide was then fibrillated in several generations in order to select for a homogenous fibril structure. This purification protocol also has the ability to purify different oligomers of Amyloid β that are interesting from a toxicity point of view. In this thesis optical characteristics and limited proteolysis with mass spectrometry are being used to studies the interactions between LCOs and fibrillated amyloid β. The proteolytic pattern was suggestive of an accessible N-terminal and a hidden C-terminal of Amyloid β M1-42 in the fibril. It was also shown that the proteolysis cleavage pattern of Chymotrypsin is not disrupted when the LCO pKTAA was used to stain fibrils. The emission spectra from the two LCOs pATAA and pKTAA changes differently when subjected to continuous excitation indicative of conformational changes or chemical modification.