Additional file 1 of Detection of skin α-synuclein using RT-QuIC as a diagnostic biomarker for Parkinson’s disease in the Chinese population

Additional file 1: Figure S1. The Impact of SDS Concentrations on RT-QuIC Reaction. Positive control: 2 μl of a 1:1,000 dilution of α-Syn fibrils. Various SDS concentrations (0.00125%, 0.001%, 0.00075%, 0.0005%, 0%) were added. At 0.00125% SDS, positive control fluorescence increased over 10 hours, reaching a peak of ~130,000. At 0.001%, 0.00075%, 0.0005%, and 0% SDS, fluorescence intensity decreased. The negative control showed increased fluorescence only at 0.00125% SDS. Figure S2. RT-QuIC Reaction Curves for Diluted α-Syn Fibrils and Fibrils with Negative Control Skin Matrix. Negative control groups plateau at 40,000 ThT fluorescence around 20 h. Diluted α-Syn fibrils show a sharp increase starting at 10 h, reaching a peak ThT fluorescence of 160,000. Figure S3. Biochemical and Morphological Analyses of RT-QuIC Products. (Figure S3A, B): AFM (The scale bar represents 400 nm) and TEM (The scale bar represents 200 nm) images reveal fibrillary structures in PD-seeded reactions, while control samples show no fibril formation. (Figure S3C): Congo red staining highlights amyloid aggregates in PD-seeded reactions, with control samples lacking observable amyloid structures. The scale bar represents 200 μm. Figure S4. ROC Curve Analysis of α-Syn Seeding Activity. ROC curve analysis comparing α-Syn seeding activity between PD and controls reveals a significant difference in normalized data (P<0.001). Figure S5. Representative Patients' Reaction Wells with Relative Fluorescence Units (RFU).