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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 | 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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Comments
Oleg Boyarkine (April 20, 2015 11:31 AM)
1) The affiliation of O. Boyarkin and V. Kopysov is written incorrectly: it has to be "EPF Lausanne".
2) There is no liquid helium cooling: instead there is a commercial fridge, which uses helium gas and electricity to compress it (like freon in your home fridge).
3) The probability for a decapeptide to have, at least, one UV absorbing residue is near 80%
Celia Arnaud (April 28, 2015 8:28 AM)
It's our style to refer to use the abbreviation ETH (i.e., the German abbreviation) for all the Swiss Federal Institutes of Technology, whether they are in the German-speaking or French-speaking regions of the country. Thus, we use ETH Lausanne to refer to EPFL even though its name is in French. About the cooling, we will be correcting the concentrate to delete the word cryogenically.
Celia Arnaud (April 29, 2015 8:15 AM)
I see what the problem is now. The ions are cryogenically cooled, but with compressed helium gas rather than liquid helium. Reilly misunderstood the type of cryogenic cooling involved.

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