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Analytical Chemistry

Two-Pronged Peptide Fingerprinting With UV And Mass Spec

Analytical Techniques: Coupling UV spectroscopy with high-resolution mass spectrometry yields structurally specific fingerprints

by Celia Henry Arnaud
April 20, 2015 | A version of this story appeared in Volume 93, Issue 16

High-resolution mass spectrometry is a wonder for identifying similar molecules in a mixture, but users of the technique still have a hard time distinguishing isomers. Oleg V. Boyarkin and Vladimir Kopysov of ETH Lausanne and Alexander Makarov of Thermo Fisher Scientific have found a way to improve structural identification of isomeric biomolecules by combining ultraviolet spectroscopy with high-resolution mass spec (Anal. Chem. 2015, DOI: 10.1021/acs.analchem.5b00822). They use UV laser pulses to break apart cryogenically cooled ions and measure the mass spectrum of the resulting fragments with an Orbitrap mass spectrometer. The two-dimensional spectra provide structurally specific fingerprints, which the researchers used to distinguish peptide stereoisomers and peptides that differ only in the site of phosphorylation. They were even able to quantitate the relative composition of mixtures. “The fundamental science is very nice, but I do not envision this becoming a practical analytical method,” says James P. Reilly of Indiana University. Few peptide residues absorb UV light, and high-resolution UV spectra of various peptides are not predictable, Reilly notes. For most labs, the combination of a liquid helium-cooled ion storage system, an Orbitrap mass spectrometer, and a tunable UV laser would be prohibitively expensive, he says. But practicality, he adds, “is not everything.”


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