Synthesis, Purification and Surface Chemistry Study of α Synuclein (61-95)

Abstract

Parkinson’s disease is the second most common neurodegenerative disease and is characterized by a progressive loss of the dopaminergic neurons in substantia nigra. The degenerating dopaminergic neurons develop a hallmark deposition of Lewy bodies comprising abundant abnormal aggregates (i.e., fibrils) of α-synuclein (α-syn), which is a protein contains 140 amino acid residues.1 Despite the abundance (~1% among the total proteins) in the brain, α-syn accumulates in the presynaptic terminals where exists high concentration of amphiphilic structure (e.g., lipsomes and cell membrane) and the reason of the accumulation is not clear. α-Syn was shown to be able to form a stable Langmuir monolayer at the air-water interface by Langmuir technique, which utilizes air-water interface to mimic the amphiphilic structure in vivo. From circular dichoism and FTIR results, α-syn was found to transform from unstructured conformation in aqueous solution to α-helix at the interface. Because α-helix is stable at the interface, this transformation explains the reason of the accumulation of α-syn around the amphiphilic structure.2 On the other hand, the primary structure of α-syn constitutes three domains: N-terminal residues 1–60; the nonamyloid component (NAC) which spans residues 61–95 and is responsible for the aggregation; and residues 96–140 which comprise the negatively charged C-terminus.3 In this thesis, α-syn(61-95) was synthesized and purified. In addition, α-Syn(61-95) was shown to also form a stable Langmuir monolayer at the air-water interface.