Do charge-remote fragmentations occur under matrix-assisted laser desorption ionization post-source decompositions and matrix-assisted laser desorption ionization collisionally activated decompositions?

N-linked oligosaccharides were released from hen ovalbumin by PNGase F and derivatized with phenylhydrazine. They were then examined by matrix-assisted laser desorption/ionization (MALDI) mass spectrometry. Phenylhydrazones of N-glycans under MALDI-tandem mass spectrometry (MS/MS) and post-source decay (PSD) conditions produced relatively similar fragmentation patterns; however, more cross-ring cleavages and fragment ions corresponding to low abundance isomeric structures were detected by MS/MS and not in PSD. Most fragment ions corresponded to glycosidic cleavages with preferential loss of residues from the chitobiose core and the 3-antenna. Sialylated phenylhydrazone-N-glycans, characterized here for the first time in ovalbumin by tandem mass spectrometry, underwent losses of sialic acid residues followed the same fragmentation pathways observed with neutral derivatized glycans. The relative abundances of some fragment ions indicated the linkage position of sialic acid and provided information on the number of residues attached to the 6-antenna. Also, new structures of ovalbumin glycans were observed as part of this study and are reported here.

Section: Resultsmentioning

confidence: 49%

Matrix-assisted laser desorption/ionization tandem mass spectrometry and post-source decay fragmentation study of phenylhydrazones of N-linked oligosaccharides from ovalbumin

Lattová

Perreault

Krokhin

2004

“…This work suggests that the internal energy of the collision activated ions is within the range of 1.4 to 2.9 eV reported to be necessary for CRF [3]. These authors also noted that MALDI is not amenable to ionization of FAs [11].…”

mentioning

confidence: 64%

“…However, using the solventfree preparation method with this same mix of materials produced mass spectra of all FAs tested where the [FAϩLi] ϩ and the desired [FAϪHϩ2Li] ϩ ions dominate even the matrix ions (Figure 1). This is remarkable, especially in view of the expectation that MALDI is not suitable for producing the desired CRF ions from FAs [11]. These results demonstrate that solvent-free sample preparation is superior for this application and that taking into account ionization suppression of analyte by the matrix can lead to ionization of compound types thought not to be amenable to MALDI MS analysis.…”

Section: Resultsmentioning

confidence: 98%

“…Domingues and colleagues, for example, demonstrated CRF using MALDI post source decay and collisionally induced dissociation (CID) on fatty acids (FA) that were derivatized using a porphyrin macrocycle not only to aid desorption, but also to localize the charge site [11]. This work suggests that the internal energy of the collision activated ions is within the range of 1.4 to 2.9 eV reported to be necessary for CRF [3].…”

mentioning

confidence: 99%

See 1 more Smart Citation

Charge-remote fragmentation of lithiated fatty acids on a TOF-TOF instrument using matrix-ionization

Trimpin

Clemmer

McEwen

2007

In numerous studies charge remote fragmentation (CRF) has been shown to be a powerful technique for determination of primary structure by allowing location of double bonds, various functional groups, and branching in a variety of compound types directly by mass spectrometry. Instrumentation and ionization methods traditionally used for CRF, however, are becoming rare, in large part because ESI and MALDI have to a significant extent replaced them. Here we demonstrate that by selecting a matrix that promotes rather than suppresses ionization of fatty acids (FA) by lithium ion adduction, and using a TOF-TOF mass spectrometer for high-energy collisional activation, CRF ions are produced that allow location of double-bond and branching positions. Further, we show that by using solvent-free MALDI sample preparation methods, thus eliminating the inherent segregation of the hydrophobic fatty acid from the hydrophilic LiCl that can occur during the evaporation of solvent, the desired [FAϪHϩ2Li] ϩ ions are greatly enhanced. Because FAs can be vaporized using laser desorption, matrix assistance in desorption of the fatty acid may occur, but is not necessary. However, the matrix plays a crucial role in enhancing or suppressing ionization. For example, matrix materials with acid (e.g., 2,5-dihydroxybenzoic acid) or hydroxy groups (e.g., dithranol) compete with the FA for Li ϩ and because of the high ratio of matrix to analyte, FA lithium adduction is minimized. However, highly electron-deficient matrix materials (e.g., TCNQ) readily donate Li ϩ to FAs because of the instability associated with being positively charged. (J Am Soc Mass

“…The few studies that describe the fragmentation of tetraphenylporphyrins in the MS/MS mode [12][13][14][15][16] show that this approach gives valuable structural information about the peripheral substituents. MS/MS is expected to be useful for the chemical characterization of porphyrins because it allows a rapid identification of porphyrins in mixtures, especially those resulting from synthetic procedures.…”

mentioning

confidence: 99%

Unexpected fragmentation of β-substituted meso-tetraphenylporphyrins induced by high-energy collisional activation

Domingues

S.-Marques

Alonso

et al. 2002

Self Cite

The protonated molecules and radical cations of meso-tetraphenylporphyrins with ␤-pyrrolic substituents, when formed by fast atom bombardment (FAB) and subjected to high-energy collisions, give rise to unexpected fragment ions. The reaction involves hydrogen migration from the ortho position of the phenyl ring to the ␣ atom of the substituent, with formation of an intramolecular, six-membered ring. The process is analogous to condensed-phase cyclizations described for the same type of compounds. The fragmentation requires the presence of a double bond in the substituent group attached to the pyrrolic ring. A rearrangement process involving anchimeric assistance by the phenyl group (analogous to an ortho effect) is proposed for the formation of these ions. T he porphyrin macrocycle is present in a variety of systems found in nature and participates in numerous important biochemical functions. New porphyrins are being synthesized to mimic the natural systems. Research on porphyrins has accelerated recently because they are applicable in a variety of fields of chemistry, physics, medicine, and biology [1]. Most promising are applications as agents in photodynamic therapy in cancer treatment [2], receptor models in molecular recognition [3], and use in materials chemistry [4] owing to their optical properties and their ability to form microporous solids, conductive polymers, and sensors. The functionalization of the ␤-pyrrolic positions of meso-tetraphenylporphyrins is particularly of interest because the properties of the porphyrin macrocycle can be modified by small changes in the ␤-pyrrolic substituents [5]. The ability of these substituents to interact with the adjacent phenyl groups may lead to deviations of planarity of the porphyrin rings, affecting the chemical, spectroscopic, and other properties of the substituted porphyrins [6,7]. An example is the role of non-planar conformations of chlorophyll, vitamin B12, and cytochrome P450 in biological processes [8].Despite the increasing interest in this class of compounds, the mass spectrometric analysis of porphyrins is still relatively unexplored [9], particularly that of substituted meso-tetraphenylporphyrins [10 -16]. The few studies that describe the fragmentation of tetraphenylporphyrins in the MS/MS mode [12][13][14][15][16] show that this approach gives valuable structural information about the peripheral substituents. MS/MS is expected to be useful for the chemical characterization of porphyrins because it allows a rapid identification of porphyrins in mixtures, especially those resulting from synthetic procedures. Further, the assembly of spectral databases will make widely available the valuable structural data from MS [17,18]. Nevertheless, mass spectral data of tetraphenylporphyrins substituted in ␤-pyrrolic positions comprise only two recent reports: One on ␤-bromotetraphenylporphyrins [19,20] and another on the fragmentation of ␤-nitrotetraphenylporphyrin [16], which is the precedent for this research.In this report, we discuss the unexpected fragm...