Vibrational Signatures of Protonated, Phosphorylated Amino Acids in the Gas Phase

Abstract

Structural characterization of protonated phosphorylated serine, threonine, and tyrosine was performed using mid-infrared multiple photon dissociation (IRMPD) spectroscopy and density functional theory (DFT) calculations. The ions were generated and analyzed by an external electrospray source coupled to a Paul ion-trap type mass spectrometer. Their fragmentation was induced by the resonant absorption of multiple photons from a tunable free electron laser (FEL) beam. IRMPD spectra were recorded in the 900-1850 cm(-1) energy range and compared to the corresponding computed IR spectra. On the basis of the frequency and intensity of two independent bands in the 900-1400 cm(-1) energy range, it is possible to identify the phosphorylated residue. IRMPD spectra for a 12-residue fragment of stathmin in its phosphorylated and nonphosphorylated forms were also recorded in the 800-1400 cm(-1) energy range. The lack of spectral congestion in the 900-1300 cm(-1) region makes their distinction facile. Our results show that IRMPD spectroscopy may became a valuable tool for structural characterization of small phosphorylated peptides.

Relative Stability of Peptide Sequence Ions Generated by Tandem Mass Spectrometry

“…These combined methods have improved our understanding of the ion structure(s) in a mass spectrometer. Precursor protonated peptides [14][15][16][17], proteins [18], and sequence ions produced in collision-induced dissociation experiments [2][3][4][5][6][7] have been investigated. y m ions have been shown to behave indistinguishably from linear protonated peptides with the same sequence and charge state [9,[19][20][21], in agreement with theory [22][23][24].…”

Vibrational Signatures of S-Nitrosoglutathione as Gaseous, Protonated Species

“…Amino acids altered by post-translational modifications have also been examined by IRMPD spectroscopy, revealing characteristic IR signatures of the additional functionality, besides novel intramolecular interactions. 29 −35 In the direction of dealing with more complex systems, a variety of peptides have been sampled, and analysis of the IR spectra of the gaseous protonated species has yielded information about the backbone conformation for fairly large and flexible molecules. 36−41 The NO-releasing ability of S-nitrosocysteine and cysteine residues, of major importance not only in biological processes but also in catalytic NO production, 42 stems from the moderate homolytic bond dissociation energy of nitroso thiols which may vary from 80 to 140 kJ mol −1 .…”

Molecular Complexes of Simple Anions with Electron‐Deficient Arenes: Spectroscopic Evidence for Two Types of Structural Motifs for Anion–Arene Interactions

“…[57] The IR features of the TNB-OR À (R = CH 3 , C 2 H 5 ) complexes have been disclosed in the IR multiple-photon dissociation (IRMPD) spectrum reporting the resonance-enhanced photofragmentation process following a multiple-photon absorption in correspondence with the IRactive vibrations of the species. [58][59][60] The spectroscopic methodology is based on the coupling of the radiation output of an IR free-electron laser (FEL) with a Paul ion-trap mass spectrometer [61,62] or with a Fourier transform ion cyclotron resonance (FTICR) mass spectrometer [63,64] at the CLIO European facility. In this way, the species obtained by addition of alkoxy anions (RO…”