Desorption chemical ionization tandem mass spectrometry of polyprenyl and dolichyl phosphates

Abstract

Negative-ion desorption chemical ionization (DCI) tandem mass spectrometry was applied to the analysis of nanomole quantities of semisynthetic polyisoprenyl phosphates, the chain length of which ranged from 7 to 20 isoprene units. The DCI spectrum of all the compounds tested show the presence of independently generated ions [M-HPO3-H](-), [M-H3PO2-H](-) and [M-H3PO4-H](-) resulting from the loss of a part of or the entire phosphate group of a polyisoprenyl-P. In tandem mass spectrometry, the [M-H3PO4-H](-) fragment produces series of ions 68 mass units apart, indicative of the polyisoprenoid nature of a compound. Studies with deuterated and α-saturated polyisoprenyl phosphates demonstrated that fragmentations of the [M-H3PO4-H](-) ion proceed from both ends (α and ω) of a polyisoprenoid chain and may occur at either allylic (A) or vinylic (V) sites. Fragments of masses equal to [n×68 - 1] and [n×68 - 13] (where n is the number of isoprene units and 3≤n is less than the total number of isoprene residues within a polyisoprenoid chain) comprise the αA and ωV series, respectively, and represent the most abundant ions in tandem mass spectra of the [M-H3PO4-H](-) fragment of polyprenyl phosphates, α-Saturated dolichyl phosphates can be distinguished easily from corresponding polyprenyl phosphates not only on the basis of a 2-u shift of the [M-H3PO4-H](-) ion and the α series of fragments, but also because of the presence of an additional (A+14) series of ions 14 u heavier than fragments resulting from the allylic cleavages of an α-saturated polyisoprenoid chain. Possible mechanisms of the collision-induced dissociation reactions of polyprenyl phosphates are discussed.

Biosynthesis of D‐arabinose in mycobacteria – a novel bacterial pathway with implications for antimycobacterial therapy

“…The application of tandem mass spectrometric methods for the analysis of polyisoprenoid glycolipids was first demonstrated using preparations of polyprenyl‐phospho‐sugars isolated from M. smegmatis [61]. Desorption chemical ionization tandem mass spectrometry proved to be suitable for the structural determination of polyisoprenyl phosphates and, in particular, allowed a facile discrimination between unsaturated polyprenols and α‐saturated (dolichol) derivatives [124]. Recent developments in related desorption electrospray ionization methods for ambient analysis of complex solid‐state samples [125] will probably find new applications in the field of lipidomics and metabolomics of isoprenoid compounds.…”

Quantification of Dolichyl Phosphates Using Phosphate Methylation and Reverse-Phase Liquid Chromatography–High Resolution Mass Spectrometry

“…So far, two different analytical platforms have been used for cellular DolP analysis, first normal-phase liquid chromatography in combination with fluorescence detection , for quantification and second MS-based workflows (see, e.g., refs − ) for structural characterizations. A frequently used robust quantification method for DolPs by Hennet and co-workers is based on the conversion of non-fluorescent DolPs into their fluorescent derivatives in a multi-step procedure, which is a labor-intensive and time-consuming process for routine analyses.…”

“…A frequently used robust quantification method for DolPs by Hennet and co-workers is based on the conversion of non-fluorescent DolPs into their fluorescent derivatives in a multi-step procedure, which is a labor-intensive and time-consuming process for routine analyses. Methods based on MS workflows − usually involve qualitative analyses of DolPs, which are often poorly ionized and suppressed by highly abundant lipid species. , To our knowledge, there are currently no methods for the simultaneous qualitative and quantitative determination of DolP species from biological membranes.…”

Simple, rapid, and sensitive quantification of dolichyl phosphates using phosphate methylation and reverse-phase liquid chromatography-high resolution mass spectrometry

“…A frequently used, robust quantification method for DolPs by Hennet et al [22] is based on the conversion of nonfluorescent DolPs to their fluorescent derivatives in a multi-step procedure, which is a labor intensive and time-consuming process for routine analyses. Methods based on MS workflows [22][23][24][25][26] mostly contain qualitative analyses of DolPs, which are often poorly ionized and suppressed by highly abundant lipid species [27,28]. To our knowledge, there are currently no available methods for the simultaneous qualitative and quantitative assessment of DolP species from biological membranes.…”

“…Conventionally, two separate analytical platforms have been used for cellular DolP analysis, firstly normal-phase liquid chromatography (NPLC) combined with fluorescence detection [1,22] for quantification, and secondly MS-based workflows (see for example [22][23][24][25][26]) for structural characterizations. A frequently used, robust quantification method for DolPs by Hennet et al [22] is based on the conversion of nonfluorescent DolPs to their fluorescent derivatives in a multi-step procedure, which is a labor intensive and time-consuming process for routine analyses.…”