STRUCTURAL STUDIES OF THE PEANUT ALLERGEN PROTEIN ARA H 2
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Presented in this dissertation are comprehensive studies of the structures of the peanut allergen protein Ara h 2 and the effect of food processing (roasting) on it. A detailed elucidation of the primary structure and PTM of Ara h 2 from the raw peanuts has been described. Ara h 2 isoforms were purified and cleaved via microwave accelerated trypsin digestion. The peptide mixtures were analyzed by LC-MS/MS and targeted CID. De novo sequencing of the MS/MS spectra revealed the protein sequence of each Ara h 2 isoform. Several hydroxyproline sites have been discovered while disulfide bond structures have been partially determined. Using anti-Ara h 2 antibodies, Western blotting of 1-D gels of the raw and dark roasted peanuts was carried out in order to characterize the changes of Ara h 2 between these two samples. The result indicates that Ara h 2 may present in a much heavier form in the roasted peanuts, possibly due to crosslinking and aggregation with other proteins. Subsequent LC-MS/MS studies of trypsin digestion of five gel pieces (>100, 100-50, 50-25, 25-16 kDa) from 1-D gels of the raw and dark roasted peanuts suggests that roasting process causes the crosslinking of Ara h 2 with other proteins. This supports our results from the immunological studies.