Structural distinction among inositol phosphate isomers using high‐energy and low‐energy collisional‐activated dissociation tandem mass spectrometry with electrospray ionization

Abstract

Electrospray (ESI) collisional-activated dissociation (CAD) tandem mass spectrometric methods for the structural characterization of inositol phosphates (InsPs) using both quadrupole and sector mass spectrometers are described. Under low-energy CAD, the [M + H](+) ions of the positional isomers of inositol phosphates, including inositol mono-, bis- and trisphosphates, yield distinguishable product-ion spectra, which are readily applicable for isomer differentiation. In contrast, the product-ion spectra arising from high-energy CAD (2 keV collision energy, floating at 50%) tandem sector mass spectrometry are less applicable for isomer identification. The differences in the product-ion spectrum profiles among the aforementioned InsP isomers become more substantial and differentiation of positional isomers can be achieved when the collison energy is reduced to 1 keV (floating at 75%). These results demonstrate that the applied collision energies play a pivotal role in the fragmentations upon CAD. The product-ion spectra are similar among the positional isomers of inositol tetrakisphosphates and of inositol pentakisphosphates. Thus, isomeric distinction for these two inositol polyphosphate classes could not be established by the tandem mass spectrometric methods that have achieved such distinctions for the less highly phosphorylated inositol phosphate classes. Under both high- and low-energy CAD, the protonated molecular species of all InsPs undergo similar fragmentation pathways, which are dominated by the consecutive losses of H(2)O, HPO(3) and H(3)PO(4).

Myo‐inositol hexakisphosphate, isolated from female gametophyte tissue of loblolly pine, inhibits growth of early‐stage somatic embryos

“…Liquid chromatography-mass spectrometry of the final active fraction indicated that the active molecule is homogeneous and has a neutral monoisotopic mass of 660 Da. The LC-MS-MS spectrum under positive mode of F2-S1-Q6 at a collision energy of 40 eV was identical to those obtained at 30 and 35 eV by Hsu et al (2003). A series of prominent ions at m ⁄ z 643, 625, 607, 581, 563, 545, 527, 483, 465, 447, 429, 385, 367, 349, 287, 269, 259, 189, 179, 161, and 99 were generated by successive losses of H 2 O (18 amu), HPO 3 (80 amu), or H 3 PO 4 (98 amu) from the precursor ion at m ⁄ z 661, with some fragment ions arising from multiple pathways.…”

“…Liquid chromatography‐mass spectrometry of the final active fraction indicated that the active molecule is homogeneous and has a neutral monoisotopic mass of 660 Da. The LC‐MS‐MS spectrum under positive mode of F2‐S1‐Q6 at a collision energy of 40 eV was identical to those obtained at 30 and 35 eV by Hsu et al. (2003).…”

Detection of myo‐inositol tris pyrophosphate (ITPP) in equine following an administration of ITPP

“…Similar interpretation of ESI mass spectral fragment ions were previously reported for IHP. [18] In the negative ion mode, ITPP formed predominantly a doubly charged deprotonated ion. When subjected to collision energy of A total of five transitions for ITPP and three transitions for ITPP-d 6 were chosen for monitoring.…”

Characterisation of lipids in cell signalling and membrane dynamics by nuclear magnetic resonance spectroscopy and mass spectrometry

“…Mass spectrometry provides the sensitivity required for characterising low amounts of signalling lipids such as PtdAc, PtdIns, PtdIns(4,5)P 2 [34,55,60,66,67] and DAG [34,57]. The semi-quantitative aspect of MS is exploited for measuring relative effects of enzymes on lipid meta-bolism [57,65].…”