Figure 4

Purified E-coli α-syn is monomeric and unstructured. Each recombinant α-syn (Wt, A30P and A53T) was analyzed by size exclusion chromatography to determine the presence of monomeric, dimeric, or other higher order forms. Eluate peaks (fraction 27) were then assessed by circular dichroism spectra to define the secondary structure of the α-syn proteins (Inset). Far-UV circular dichroism spectra were recorded on an Aviv circular dichroism spectrometer model 62DS (Lakewood, NJ, USA) at 25°C using quartz cells with a path length of 0.1 cm. Spectra were obtained from 195 nm to 260 nm, with a 1.0-nm step, 1.0-nm bandwidth, and 4-s collection time per step. The experimental data were expressed as mean residue ellipticity (θ) (deg·cm²·dmol^-1). Only monomeric forms of α-syn where identified by size exclusion chromatography, and all α-syn share similar random secondary structure.