Ultraviolet photodissociation of protonated, fixed charge, and charge-reduced peptides

Abstract

The fragmentation behavior of three peptides (RGAFSTFGAS, GAFSTFGASR, and GAFSTFGASS) was evaluated by collisional activated dissociation (CAD), higher energy collisional activated dissociation (HCD), and ultraviolet photodissociation (UVPD). In particular, hybrid methods combining electron transfer with CAD, HCD, or UVPD were used to assess the impact of the location of a basic site at the C-or N-terminus, the presence of a fixed charge at the C-or N-terminus, and the presence of a radical site. The release of a mobilized proton occurred for those peptides modified with a quaternary amine at the C-or N-terminus, thus resulting in formation of C-and/or N-terminus fragment ions that would not otherwise be expected if the fixed charge remained static. Activation of charge-reduced peptides (i.e. peptide radical ions) resulted in simplified spectra compared to the corresponding even electron peptides. Interestingly, UVPD of the charge-reduced species generated similar spectra to CAD and HCD of the same precursor ions, suggesting a shift to dominant radical-induced dissociation rather than the more diverse pathways common upon photodissociation.

193 nm Ultraviolet Photodissociation Mass Spectrometry for Phosphopeptide Characterization in the Positive and Negative Ion Modes

“…Although subtle, this trend reinforces previous results demonstrating successful UVPD even for peptides with low proton mobility. 33,34 Peptide length distributions were also compared between those phosphopeptides identified by UVPD versus HCD (Figure 3E), and UVPD appeared to outperform HCD for the detection of short peptides containing fewer than 12 amino acids. Because shorter peptides are likely to carry fewer charges, the UVPD length distribution correlates well with the UVPD charge state distribution.…”

Ultraviolet Photodissociation Induced by Light‐Emitting Diodes in a Planar Ion Trap

“…Collision‐based methods continue to be the most versatile, robust, and popular activation strategies. Owing to its high energy deposition, which results in the production of rich fragmentation patterns, UVPD has become a powerful alternative activation method for the characterization of small molecules, peptides, nucleic acids, lipids, and proteins . The ability to produce intense beams of light is a significant advantage of lasers and makes them a natural fit for UVPD applications, albeit with certain technical hurdles, such as the need for alignment, special optical ports, and in many cases beam collimation and focusing to restrict the laser beam to a prescribed path in the mass spectrometer and minimize damage to other components.…”

A Novel Triethylphosphonium Charge Tag on Peptides: Synthesis, Derivatization, and Fragmentation

“…One such tag is trimethylammonium butyric acid N -hydroxysuccinimidyl ester (TMAB), which contains a quaternary nitrogen atom [19, 21–24]. Unfortunately, activation of peptides derivatized with TMAB results in unusual fragmentation pathways, including cyclization of the charge tag to generate a mobile proton and rearrangement of methyl groups from the quaternary ammonium ion [25].…”

“…Unfortunately, activation of peptides derivatized with TMAB results in unusual fragmentation pathways, including cyclization of the charge tag to generate a mobile proton and rearrangement of methyl groups from the quaternary ammonium ion [25]. Another popular label is tris (trimethoxyphenyl) phosphonium acetic acid N -hydroxysuccinimidyl ester (TMPP), which includes a quaternary phosphonium ion with three bulky trimethoxyphenyl groups [16, 20, 24, 26]. This stable tag has been reported to be more hydrophilic than the somewhat simpler triphenylphosphonium label due to its trimethoxy groups [16].…”