SYNTHESIS, PURIFICATION, SOLUBILITY, AND RAMAN SPECTROSCOPY STUDY OF VARIOUS SEGMENTS OF THE PROTEIN α-SYNUCLEIN’S NONAMYLOID-BETA COMPONENT REGION

Abstract

Parkinson’s Disease is a neurodegenerative brain disorder that occurs when dopamine producing neurons, in the mid-region of the brain known as the substantia nigra, stop working or die. The degenerating dopaminergic neurons develop a hallmark deposition of Lewy bodies comprised mostly of a 140 amino acid residue protein known as α-synuclein. The primary structure of α-synuclein consists of three components: 1) the N-terminus domain (amino acid residues 1-60), which contains a positively charged lysine residue; 2) the hydrophobic domain (residues 61-95), which is the central part of the protein, and is known as the nonamyloid-beta component (NAC); 3) the C-terminus domain (residues 96-140), which is negatively charged and rich in acidic residues. It has been determined that the NAC is hydrophobic and known to be the source of aggregation within α-synuclein that causes Parkinson’s Disease. Previously published results from our lab determined that the NAC shares similar biophysical behavior to that of the whole protein of α-synuclein. On the other hand, it was very insoluble and had weak Raman spectroscopic peaks. For this thesis, the goal was to try to improve the solubility of the NAC region by synthesizing shorter and longer length nonamyloid-beta component (NAC) regions of α-synuclein, observe which are more soluble in water, and analyze each pure peptide using Raman spectroscopy in order to determine if any displayed stronger signals than that of the NAC. It was concluded that all studied variations of the NAC had much greater solubility, but α-synuclein (57-102) had substantially improved Raman spectra signals.