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IRMPD Spectroscopy of a Protonated, Phosphorylated Dipeptide
Author(s) -
Correia Catarina F.,
Clavaguera Carine,
Erlekam Undine,
Scuderi Debora,
Ohanessian Gilles
Publication year - 2008
Publication title -
chemphyschem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.016
H-Index - 140
eISSN - 1439-7641
pISSN - 1439-4235
DOI - 10.1002/cphc.200800469
Subject(s) - infrared multiphoton dissociation , chemistry , dipeptide , protonation , fourier transform ion cyclotron resonance , infrared spectroscopy , spectroscopy , mass spectrometry , ion , conformational isomerism , dissociation (chemistry) , analytical chemistry (journal) , photochemistry , molecule , amino acid , physics , organic chemistry , biochemistry , quantum mechanics , chromatography
The protonated, phosphorylated dipeptide [GpY+H] + is characterized by mid‐infrared multiple‐photon dissociation (IRMPD) spectroscopy and quantum‐chemical calculations. The ions are generated in an external electrospray source and analyzed in a Fourier transform ion cyclotron resonance mass spectrometer, and their fragmentation is induced by resonant absorption of multiple photons emitted by a tunable free‐electron laser. The IRMPD spectra are recorded in the 900–1730 cm −1 range and compared to the absorption spectra computed for the lowest energy structures. A detailed calibration of computational levels, including B3LYP‐D and coupled cluster, is carried out to obtain reliable relative energies of the low‐energy conformers. It turns out that a single structure can be invoked to assign the IRMPD spectrum. Protonation at the N terminus leads to the formation of a strong ionic hydrogen bond with the phosphate PO group in all low‐energy structures. This leads to a PO stretching frequency for [GpY+H] + that is closer to that of [pS+H] + than to that of [pY+H] + and thus demonstrates the sensitivity of this mode to the phosphate environment. The COP phosphate ester stretching mode is confirmed to be an intrinsic diagnostic for identification of which type of amino acid is phosphorylated.