Abstract: Objective To screen for the potential protein biomarkers in serum of patients with Parkinson's disease.Methods The sera from patients with idiopathic PD and healthy blood donors were profiled by matrix assisted laser desorption/ionization time of flight mass spectrometer(MALDI-TOF-MS) combined with weak cationic exchange magnetic beads(WCX-MB).The differential expression proteins were analyzed with statistical method.A M/Z2260.1 peptide was identified by LC-MALDI-TOF/TOF,and concentration of the intact protein containing M/Z2260.1 was determined by ELISA.Results Overall,107 protein peaks were detected in a mass range of 1 000～50 000.Of these,9 proteins were differentially expressed in the serum between PD patients and normals(P<0.01).A 2260.1u peptide was specifically expressed in serum in PD patients.It was sequenced as G.KFKSGFPQVSMFFTHTFPK,and was identified as a fragment deriving from C-terminal of histidine-rich glycoprotein(HRG).ELISA show that the HRG concentration in serum in PD were significantly decreased(P<0.05).Conclusion Expression of the low molecular weight proteins in serum in PD was significantly different from the healthy controls.Although HRG concentration in serum in PD patients is lower than that of healthy controls,the M/Z2260.1 peptide,a C-terminal fragment of the HRG,is markedly increased in serum of PD patients.

Key words: Parkinson's disease(PD), histidine-rich glycoprotein(HRG), biomarkers, proteomics