Influence of side chain chemistry on fragmentation pathways of b3-45 ions. (2011)

Undergraduates: Meredith Arnold, Alessandra L. Ferzoco, Sandra E. Spencer

Faculty Advisor: Gary Glish
Department: Chemistry

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Although much work has been done to improve the ability to understand peptide fragmentation, further information is still required in order to fully understand the fragmentation pathways. Most current fragmentation mechanisms focus on peptide backbone structure but future explanations should include side chain chemistry as well.
Collision induced dissociation of b3-45 ions from YXZFL show evidence of a side chain loss channel. This has been observed when X is alanine or glycine and Z is alanine, glycine, valine, leucine, or proline. Neutral loss of 147 Da and detection of a product ion at m/z 120 would seem to indicate phenylalanine, which is unexpected because phenylalanine should not be present in the b3-45 ion. It is possible that these losses can be explained by participation of the tyrosine side chain in the rearrangement/dissociation chemistry. Preliminary results confirm this theory because tyrosine loss and the tyrosine immonium ion are not detected in the b3-45 dissociation pathways, whereas they are observed in the dissociation of b3 ions.