Comparison of CID, ETD and metastable atom-activated dissociation (MAD) of doubly and triply charged phosphorylated tau peptides.

The fragmentation behavior of the 2+ and 3+ charge states of eleven different phosphorylated tau peptides was studied using collision-induced dissociation (CID), electron transfer dissociation (ETD) and metastable atom-activated dissociation (MAD). The synthetic peptides studied contain up to two known phosphorylation sites on serine or threonine residues, at least two basic residues, and between four and eight potential sites of phosphorylation. CID produced mainly b-/y-type ions with abundant neutral losses of the phosphorylation modification.

Classification of cultivation locations of Panax quinquefolius L samples using high performance liquid chromatography-electrospray ionization mass spectrometry and chemometric analysis.

Panax quinquefolius L ( P. quinquefolius L) samples grown in the United States and China were analyzed with high performance liquid chromatography-mass spectrometry (HPLC-MS). Prior to classification, the two-way data sets were subjected to pretreatment including baseline correction and retention time (RT) alignment.

Metastable atom-activated dissociation mass spectrometry of phosphorylated and sulfonated peptides in negative ion mode.

The dissociation behavior of phosphorylated and sulfonated peptide anions was explored using metastable atom-activated dissociation mass spectrometry (MAD-MS) and collision-induced dissociation (CID). A beam of high kinetic energy helium (He) metastable atoms was exposed to isolated phosphorylated and sulfonated peptides in the 3- and 2- charge states. Unlike CID, where phosphate losses are dominant, the major dissociation channels observed using MAD were C(α) - C peptide backbone cleavages and neutral losses of CO(2), H(2)O, and [CO(2) + H(2)O] from the charge reduced (oxidized) product ion, consistent with an electron detachment dissociation (EDD) mechanism such as Penning ionization.

Characterization of tyrosine nitration and cysteine nitrosylation modifications by metastable atom-activation dissociation mass spectrometry.

The fragmentation behavior of nitrated and S-nitrosylated peptides were studied using collision induced dissociation (CID) and metastable atom-activated dissociation mass spectrometry (MAD-MS). Various charge states, such as 1+, 2+, 3+, 2-, of modified and unmodified peptides were exposed to a beam of high kinetic energy helium (He) metastable atoms resulting in extensive backbone fragmentation with significant retention of the post-translation modifications (PTMs). Whereas the high electron affinity of the nitrotyrosine moiety quenches radical chemistry and fragmentation in electron capture dissociation (ECD) and electron transfer dissociation (ETD), MAD does produce numerous backbone cleavages in the vicinity of the modification.

Metastable atom-activated dissociation mass spectrometry: leucine/isoleucine differentiation and ring cleavage of proline residues.

Extensive backbone fragmentation resulting in a-, b-, c-, x-, y- and z-type ions is observed of singly and doubly charged peptide ions through their interaction with a high kinetic energy beam of argon or helium metastable atoms in a modified quadrupole ion trap mass spectrometer. The ability to determine phosphorylation-sites confirms the observation with previous reports and we report the new ability to distinguish between leucine and isoleucine residues and the ability to cleave two covalent bonds of the proline ring resulting in a-, b-, x-, y-, z- and w-type ions. The fragmentation spectra indicate that fragmentation occurs through nonergodic radical ion chemistry akin to electron capture dissociation (ECD), electron transfer dissociation (ETD) and electron ionization dissociation mechanisms.