Related Experiment Video
Updated: Apr 29, 2026

Determination of the Gas-phase Acidities of Oligopeptides
Published on: June 24, 2013
Differentiating sulfopeptide and phosphopeptide ions via resonant infrared photodissociation
Amanda L Patrick1, Corey N Stedwell, Nicolas C Polfer
1Department of Chemistry, University of Florida , P.O. Box 117200, Gainesville, Florida 32611, United States.
Abstract:
The post-translational modifications sulfation and phosphorylation pose special challenges to mass spectral analysis due to their isobaric nature and their lability in the gas phase, as both types of peptides dissociate through similar channels upon collisional activation. Here, we present resonant infrared photodissociation based on diagnostic sulfate and phosphate OH stretches, as a means to differentiate sulfated from phosphorylated peptides within the framework of a mass spectrometry platform. The approach is demonstrated for a number of tyrosine-containing peptides, ranging from dipeptides (YG, pYG, and sYG) over tripeptides (GYR, GpYR, and GsYR), to more biologically relevant enkephalin peptides (YGGFL, pYGGFL, and sYGGFL). In all cases, the diagnostic ranges for sulfate OH stretches are established as 3580-3600 cm(-1) and can thus be distinguished from other characteristic hydrogen stretches, such as carboxylic acid OH, alcohol OH, and phosphate OH stretches.
Related Concept Videos
Peptide Identification Using Tandem Mass Spectrometry
This technique helps gather information regarding the protein from which the peptide was obtained and to study the peptides’ amino acid sequence. Identifying peptides from a complex mixture is an important component of the growing field of...
Mass Spectrum: Interpretation
Mass Spectrometry: Molecular Fragmentation Overview
One type of fragmentation pattern is the cleavage of a single bond in the molecular ion. The cleavage leads to a radical and a cation. The cleavage can occur at...
Preparation and Reactions of Sulfides
¹³C NMR: Distortionless Enhancement by Polarization Transfer (DEPT)
IR Spectrum Peak Broadening: Hydrogen Bonding
However, the extent of hydrogen bonding influences the observed stretching frequency and band broadening. Intermolecular or intramolecular...

