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1. Developing qualitative LC-MS methods for characterization of Vaccinium berry Standard Reference Materials
Mark S Lowenthal, Melissa Meaney Phillips, Catherine A Rimmer, Paul A Rudnick, Yamil Simon, Stephen E Stein, Karen W Phinney
2. Effect of N-Terminal Glutamic Acid and Glutamine on Fragmentation of Peptide Ions
Bhaskar Godugu, Pedatsur Neta, Yamil Simon, Stephen E Stein
A prominent dissociation path for electrospray generated tryptic peptide ions is the dissociation of the peptide bond linking the second and third residues from the amino-terminus. The formation of the resulting b^d2^ and y^dn-2^ fragments has been r ...
3. Electrospray Tandem Quadrupole Fragmentation of Quinolone Drugs and Related Ions. On the Reversibility of Water Loss from Protonated Molecules
Pedatsur Neta, Bhaskar Godugu, Yuxue Liang, Yamil Simon, Xiaoyu Yang, Stephen E Stein
Selected reaction monitoring (SRM) of quinolone drugs showed1 different sensitivities in aqueous solution vs. biological extract. The authors suggested formation of two singly protonated ions with different behavior, one undergoing loss of H^d2^O and ...
4. Loss of 45 Da from a2 Ions and Preferential Loss of 48 Da from a2 Ions Containing Methionine in Peptide Ion Tandem Mass Spectra
Yamil Simon, Pedatsur Neta, Xiaoyu Yang, Stephen E Stein
While analyzing tandem mass spectra of tryptic tripeptides, intense unassigned peaks were observed, which correspond to a neutral loss of 45 Da from a^d2^ ions. From exact mass analysis this loss is ascribed to formamide (or NH^d3^+CO). Elimination o ...
5. Loss of H2 and CO from Protonated Aldehydes in Electrospray Ionization Mass Spectrometry
Pedatsur Neta, Yamil Simon, Yuxue Liang, Stephen E Stein
Electrospray ionization mass spectrometry of 3-formylchromones and 3-formylcoumarins shows that
collision-induced dissociation of the protonated ions results in elimination of H¬¬2 as a major
fragmentation route. This loss of H2 yields an unstabl ...
6. Metabolite Profiling of a NIST Standard Reference Material for Human Plasma (SRM 1950) ‹ GC/MS, LC/MS, NMR and Clinical Laboratory Analyses, Libraries and Web-based resources
Yamil Simon, Mark S Lowenthal, Lisa Ervin Kilpatrick, Maureen L Sampson, Kelly H Telu, Paul A Rudnick, William Gary Mallard, Daniel W Bearden, Tracey Beth Schock Schock, Dmitrii V Tchekhovskoi, Niksa Blonder, Xinjian Yan, Yuxue Liang, Yufang Zheng, William E Wallace, Pedatsur Neta, Karen W Phinney, Alan T. Remaley, Stephen E Stein
Recent progress in metabolomics and the development of increasingly sensitive analytical techniques have renewed interest in global profiling, i.e., semi-quantitative monitoring of all chemical constituents of biological fluids. In this work, we have ...
7. Pairwise Alignment of Chromatograms using a Fisher-Rao Metric
William E Wallace, Anuj Srivastava, Kelly H Telu, Yamil Simon
A new approach to aligning chromatograms is introduced and applied to examples of metabolite identification by liquid chromatography mass spectrometry (LC MS). A square root representation of the chromatogram‰s derivative coupled with a Fisher Rao R ...
8. Reaction of Arylium Ions with the Collision Gas N2 in Electrospray Ionization Mass Spectrometry
Yuxue Liang, Pedatsur Neta, Yamil Simon, Stephen E Stein
RATIONALE: Tandem mass spectra of many compounds contained peaks which could not arise from the
precursor ion and were different in different instruments. Such peaks were found to be due to
reaction of arylium ions with N2 in the collision cell. ...
9. Unexpected Peaks in Tandem Mass Spectra due to Reaction of Product Ions with Water in Mass
Spectrometer Collision Cells
Pedatsur Neta, Mahnaz Farahani, Yamil Simon, Yuxue Liang, Xiaoyu Yang, Stephen E Stein
While determining the fragmentation pathways of positive ions of drugs, pesticides, metabolites, and
other compounds, using electrospray ionization mass spectrometry, we noticed that certain product
ions react with water in the collision cell. Th ...