Characteristic Fingerprint Spectrum of α-Synuclein Mutants on Terahertz Time-Domain Spectroscopy

Abstract

ObjectiveAlpha-Synuclein (α-Syn), a presynaptic neuronal protein encoded by the SNCA gene, is involved in the pathogenesis of Parkinson's disease. Point mutations and multiplications of the α-Syn (A30P and A53T) are correlated with early-onset Parkinson's disease characterized by rapid progression and poor prognosis. Currently, the clinical identification of SNCA variants, especially disease-related A30P and A53T mutants, remains challenging and also time-consuming. This study has aimed to develop a novel label-free detection method for distinguishing the SNCA mutants using transmission terahertz (THz) time-domain spectroscopy. MethodsThe protein was spin-coated onto the quartz to form a thin film, which was measured using THz time-domain spectroscopy. The spectral characteristics of THz broadband pulse waves of α-Syn protein variants (SNCA wild type [WT], A30P, and A53T) at different frequencies were analyzed via Fourier transform. ResultsThe amplitude A intensity (AWT, AA30P, and AA53T) and peak occurrence time in THz-TDS sensitively distinguished the three protein variants. The phase φ difference in THz frequency domain followed the trend of φWT>φA30P>φA53T. There was a significant difference in THz frequency amplitude A’ corresponding to the frequency ranging from 0.4 THz to 0.66 THz (A’A53T>A’A30P>A’WT). At a frequency of 0.4-0.6 THz, the transmission T of THz waves distinguished three variants (TA53T>TA30P>TWT), while there was no difference in the transmission T at 0.66 THz. ConclusionThe SNCA wild-type protein and two mutant variants (A30P and A53T) had distinct characteristic fingerprint spectra on THz time-domain spectroscopy. This novel label-free detection method has great potential for the differential diagnosis of Parkinson's disease subtypes.