Targeted annotation of peptides by selective infrared multiphoton dissociation mass spectrometry

Published February 27, 2018

Schematic of LC/MS approach that leverages the high IR absorbance of sulfoxides for selective dissociation and discovery of S-sulfonated peptides.

Protein oxidative damage is a common occurrence in a number of diseases, including cancer, neurodegenerative, and cardiovascular disease. Yet, little is known about its contribution to these illnesses. We developed a new technique, utilizing an infrared laser in combination with a mass spectrometer, to selectively identify sites of oxidation in complex protein mixtures. This sensitive and rapid platform may outperform current techniques and thus shed light on the involvement of oxidative damage in each of these diseases.

First, some background

Reactive oxygen species (e.g., hydrogen peroxide) are important second messengers in cellular signaling. In proteins, the amino acid cysteine is particularly susceptible to being oxidized as a post-translational modification (PTM). PTM refers to the modification of a protein following its synthesis by RNA.

What did scientists discover?

High-magnetic-field ion cyclotron resonance (ICR) enabled the development of a new method to rapidly determine oxidative products of sulfur amino acids in proteins by using a CO₂ laser to selectively break specific chemical bonds.

Why is this important?

Mis-regulation of the oxidation of cysteine has been linked to hypertension, cancer, aging and neurodegenerative diseases. Other techniques are too insensitive to identify all sulfonic acid-containing peptides following protein oxidation.

Who did the research?

Borotto, N.B.¹, McClory, P.J.¹, Martin, B.R.¹, Hakansson, K.¹

¹Department of Chemistry, University of Michigan

Why did they need the MagLab?

The selective infrared multiphoton dissociation (IRMPD) technique was able to significantly fragment oxidized peptides to rapidly identify modified peptides. Importantly, IRMPD-generated ions often allowed the localization and assignment of the post-translational modification to a single amino acid residue. The ability to rapidly identify and sequence modified peptides in a single liquid chromatography mass spectrometry (LC/MS) run is a unique capability of the MagLab’s 9.4 T ICR mass spectrometry system.