Wisconsin Alumni Research Foundation

University of Illinois

Casey J Krusemark

Lloyd M Smith

Joshua J Coon

Brian L Frey

Madhusudan Patel

Peter Jeremy Belshaw

Michael Robert Shortreed

Neil L Kelleher

Margaret F Phillips

Shane M Lamos

April L Jue

The present invention provides methods for enhancing the fragmentation of peptides for mass spectrometry by modifying the peptides with a tagging reagent containing a functional group, such as a tertiary amine, having a greater gas-phase basicity than the amide backbone of the peptide. These high gas-phase basicity functional groups are attached to a peptide by reacting the tagging reagent to one or more available carboxylic acid groups of the peptide. Linking these high gas-phase functional groups to the peptides leads to higher charge state ions from electrospray ionization mass spectrometry (ESI-MS), which fragment more extensively during fragmentation techniques, particularly non-ergodic fragmentation techniques such as electron capture dissociation (ECD) and electron transfer dissociation (ETD).

Labeling peptides with tertiary amines and other basic functional groups for improved mass spectrometric analysis

Relative quantification of metabolites by Electrospray Ionization Mass Spectrometry (ESI-MS) requiring a mechanism for simultaneous analysis of multiple analytes in two or more samples. Labeling reagents that are reactive to particular compound classes and differ only in their isotopic compositions facilitate relative quantification. Heavy and light isotopic forms of methylacetimidate were synthesized and used as labeling reagents for quantification of amine-containing molecules. Heavy and light isotopic forms of formaldehyde and cholamine were also synthesized and used independently as labeling reagents for quantification of amine-containing and carboxylic acid-containing molecules, such as found in biological samples. The labeled end-products are positively charged under normal acidic conditions involving conventional Liquid Chromatography Mass Spectrometry (LC/MS) applications. Labeled primary and secondary amine and carboxylic acid end-products generated higher signals concerning mass-spectra than pre-cursor molecules and improved sensitivity. Improved accuracy concerning relative quantification was demonstrated by mixing heavy and light labeledextracts in different ratios.

Ionizable isotopic labeling reagents for relative quantification by mass spectrometry

Relative quantification of metabolites by Electrospray Ionization Mass Spectrometry (ESI-MS) requiring a mechanism for simultaneous analysis of multiple analytes in two or more samples. Labeling reagents that are reactive to particular compound classes and differ only in their isotopic kit facilitating relative quantification and providing tangible evidence for the existence of specific functional groups. Heavy and light isotopic forms of methylacetimidate were synthesized and used as labeling reagents for quantification of amine-containing molecules, such as biological samples. Heavy and light isotopic forms of formaldehyde and cholamine were also synthesized and used independently as labeling reagents for quantification of amine-containing and carboxylic acid-containing molecules, such as found in biological samples. Advantageously, the labeled end-products are positively charged under normal acidic conditions involving conventional Liquid Chromatography Mass Spectrometry (LC/MS) applications. Labeled primary and secondary amine and carboxylic acid end-products also generated higher signals concerning mass-spectra than pre-cursor molecules and improved sensitivity. Improved accuracy concerning relative quantification was achieved by mixing heavy and light labeledextracts in different ratios. Labeling strategy was further employed to ascertain differences in the amounts of amine-containing metabolites for two strains ofseeds.

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Woodside, CA, United States of America

Casey J Krusemark