Evidence of diketopiperazine and oxazolone structures for HA b2+ ion.
Peptide fragmentation can lead to an oxazolone or diketopiperazine b(2)(+) ion structure. IRMPD spectroscopy combined with computational modeling and gas-phase H/D exchange was used to study the structure of the b(2)(+) ion from protonated HAAAA. The experimental spectrum of the b(2)(+) ion matches both the experimental spectrum for the protonated cyclic dipeptide HA (a commercial diketopiperazine) and the theoretical spectrum for a diketopiperazine protonated at the imidazole pi nitrogen. A characteristic band at 1875 cm(-1) and increased abundance of the peaks at 1619 and 1683 cm(-1) indicate a second population corresponding to an oxazolone species. H/D exchange also shows a mixture of two populations consistent with a mixture of b(2)(+) ion diketopiperazine and oxazolone structures.
Perkins
Brittany R
BR
Department of Chemistry and Biochemistry, University of Arizona, Tucson, Arizona 85721, USA.
Chamot-Rooke
Julia
J
Yoon
Sung Hwan
SH
Gucinski
Ashley C
AC
Somogyi
Arpád
A
Wysocki
Vicki H
VH
D041961:Deuterium Exchange Measurement; D054659:Diketopiperazines / Q000737:chemistry*; D004151:Dipeptides / Q000737:chemistry*; D008958:Models, Molecular; D010081:Oxazolone / Q000737:chemistry*; D010456:Peptides, Cyclic / Q000737:chemistry*; D017785:Photons; D011487:Protein Conformation; D013057:Spectrum Analysis
D054659:Diketopiperazines; D004151:Dipeptides; D010456:Peptides, Cyclic; D010081:Oxazolone