Total Apolipoprotein E and Apolipoprotein E4 isoform assay (n=672) by targeted mass spectrometry: a pilot assay for methionine-containing proteotypic peptide

摘要

We present here a robust method to determine absolute levels of methionine containing peptides. We propose to completely and irreversibly oxidize methionine in methionine-sulfone with performic acid in presence of phenol. This protocole was applied in plasma to quantify total Apolipoprotein E and to specifically quantify Apolipoprotein E4, a protein probably implicated in Alzheimer disease. We performed UHPLC separation in only 5 minutes (including reconditionning step) in 672 clinical samples. Results show no statistically differences in total Apo E or Apo E4 plasma levels between AD patients and controls which confirms controversial results obtained in ELISA.