Parkinson's (PD) is a progressive disorder that affects the nervous system and is characterized by the degradation of dopaminergic neurons in the substantial nigra. Alpha-synuclein has been shown to play a central role in the pathogenesis of idiopathic PD(iPD). Progress in developing disease-modifying therapies in PD is limited by a lack of objective diagnostic biomarkers. This includes an early and accurate diagnosis as well as continuous monitoring of disease progression and therapy response. The cerebrospinal fluid (CSF) is a biofluid of particular interest to study biomarkers since it is closest to the brain structures and therefore could serve as an ideal source to reflect ongoing pathologic processes. Monitoring of disease progression and treatment response is more challenging due to the invasive nature of repeated lumbar puncture. Thus, there is a need for blood-based biomarkers that can be used to diagnose or monitor progression of iPD. The measurement of alpha-syn in plasma has failed to serve as a biomarker, but there are reports that phosphorylated alpha synuclein, measured by ELISA, in red blood cells (RBCs) has potential as a diagnostic tool. Utilizing this information, we wanted to explore the phospho-proteome of RBC’s to see 1) if alpha synuclein can be phosphorylated at several sites and 2) are there any other phospho-peptides that are disease specific. To do this we use a cohort of iPD and control patient RBCs in combination with the Assay Map Bravo for the phospho-enrichment and a TIMS-TOF for peptide identification and quantitation.