title: Sensitive analysis of α-synuclein by nonlinear laser wave mixing coupled with capillary electrophoresis.
abstract: Multi-photon nonlinear laser wave-mixing spectroscopy is a novel absorption-based technique that offers excellent detection sensitivity for biomedical applications, including early diagnosis and investigation of neurodegenerative diseases. α-Synuclein is linked to Parkinson's disease (PD), and characterization of its oligomers and quantification of the protein may contribute to understanding PD. The laser wave-mixing signal has a quadratic dependence on analyte concentration, and hence the technique is effective in monitoring small changes in concentration within biofluids. A wide variety of labels can be employed for laser wave-mixing detection due to its ability to detect both chromophores and fluorophores. In this investigation, two fluorophores and a chromophore are studied and used as labels for the detection of α-synuclein. Wave-mixing detection limits of PD-related protein conjugated with fluorescein isothiocyanate, QSY 35 acetic acid, succinimidyl ester, and Chromeo P503 were determined to be 1.4 × 10(-13) M, 1.4 × 10(-10) M, and 1.9 × 10(-13) M, respectively. Based on the laser probe volume used, the corresponding mass detection limits were determined to be 1.1 × 10(-23) mol, 1.1 × 10(-20) mol, and 1.5 × 10(-23) mol. This study also presents molecular-based separation and quantification of α-synuclein by laser wave mixing coupled with capillary electrophoresis.
authors.affiliation: Department of Chemistry and Biochemistry, San Diego State University, San Diego, CA 92182, USA.
authors.forename: Manna F
authors.initials: MF
authors.lastname: Iwabuchi
authors.affiliation: Department of Chemistry and Biochemistry, San Diego State University, San Diego, CA 92182, USA.
authors.forename: Marcel M
authors.initials: MM
authors.lastname: Hetu
authors.affiliation: Department of Chemistry and Biochemistry, San Diego State University, San Diego, CA 92182, USA. Electronic address: william.tong@sdsu.edu.
authors.forename: William G
authors.initials: WG
authors.lastname: Tong
mesh_terms: D000595:Amino Acid Sequence; D019075:Electrophoresis, Capillary / Q000379:methods*; D008970:Molecular Weight; D017711:Nonlinear Dynamics; D013056:Spectrophotometry, Ultraviolet; D051844:alpha-Synuclein / Q000032:analysis* / Q000737:chemistry
chemical_list: D051844:alpha-Synuclein
keywords: Electrophoresis; Parkinson's disease; Ultrasensitive nonlinear spectroscopy; α-Synuclein