Comparison of Targeted Mass Spectrometry Techniques with an Immunoassay: A Case Study for HSP90α.

Purpose: The objective of this study is to better understand factors governing the variability and sensitivity in SRM and PRM, compared to immunoassay.

Experimental Design: A 2D-LC-MS/MS-based SRM and PRM assay is developed for quantitative measurements of HSP90α in serum. Forty-three control sera are compared by SRM, PRM, and ELISA following the manufacturer's instructions.

Chemical labeling of electrochemically cleaved peptides.

Rationale: Cleavage of peptide bonds C-terminal to tyrosine and tryptophan after electrochemical oxidation may become a complementary approach to chemical and enzymatic cleavage. A chemical labeling approach specifically targeting reactive cleavage products is presented here and constitutes a promising first step towards the development of a new proteomics workflow.

Methods: Hexylamine was used to react with the spirolactone moieties generated after electrochemical oxidation and cleavage of tripeptides.