Loss of internal 1 → 6 substituted monosaccharide residues from underivatized and per- O -methylated trisaccharides

In this communication, the structural analysis of six synthetic O-Linked amphiphilic cholesteryl polyethoxy neoglycolipids containing N-acetyl-D-glucosamine was performed by electrospray ionization mass spectrometry in the positive ion mode, with a QqTOF-MS/MS hybrid instrument. The MS/MS analyses provided evidence for the "in situ" formation, in the collision cell of the tandem mass spectrometer, of an unexpected and unique [C-glycoside] ϩ product ion, resulting from an ion-molecule reaction between the N-acetyl-D-glucosamine oxonium ion and the neutral cholesta-3,5-diene molecule. Quasi T he structural diversity of complex carbohydrates of cell surface membranes has been much more appreciated over the last two decades, due to the vast improvement in analytical techniques.We have synthesized a series of amphiphilic neoglycolipid cholesteryl derivatives (see Scheme 1), in which the cholesterol and carbohydrate (N-acetyl-D-glucosamine) moieties were attached by means of a polyethoxy variable spacer [1,2]. Synthetic neoglycolipids have been successfully incorporated into liposomal formulations to prolong their half lives as alternative to pegylated liposomes (PEG-liposomes) [3,4]. More recently, novel series of neoglycolipids bearing various sugar monomers or oligomers have been evaluated as stabilizing agents for cationic liposomes [5] which are one of the most important nonviral gene carriers used in cancer gene therapy [6]. In this study, neoglycolipid-stabilized liposomes were superior to PEG-stabilized liposomes in terms of gene transfer efficiency [5].In the present communication, we report the "in situ" formation, both in the collision cell and the ESI interface of the tandem mass spectrometer, of an unexpected and unique [C-glycoside] ϩ product ion, resulting from an ion-molecule reaction between the N-acetyl-D-glucosamine oxonium ion and the neutral cholesta-3,5-diene molecule. We also propose the fragmentation routes of these synthetic amphiphilic cholesteryl polyethoxy neoglycolipids by electrospray ionization mass spectrometry with a QqTOF-MS hybrid instrument. The low-energy collision induced dissociation (CID) tandem mass spectrometric analyses are also described.

Section: Low-energy Cid-ms/ms Of the Precursor Protonated Molecules Omentioning

confidence: 99%

In situ formation of C-glycosides during electrospray ionization tandem mass spectrometry of a series of synthetic amphiphilic cholesteryl polyethoxy neoglycolipids containing N-acetyl-D-glucosamine

Banoub

Boullanger

Lafont

et al. 2005

“…To the best of our knowledge, long-range transfers during CID experiments have only been reported twice in the literature [50,51]. Examples for short-range transfers (over one saccharide residue) have been reported for several linear and branched oligosaccharides [52][53][54]. Thomas-Oates and co-workers [52,53] reported internal residue losses that were due to short-range transfers.…”

mentioning

confidence: 98%

“…Examples for short-range transfers (over one saccharide residue) have been reported for several linear and branched oligosaccharides [52][53][54]. Thomas-Oates and co-workers [52,53] reported internal residue losses that were due to short-range transfers. Earlier, McNeil [54] had observed the phenomenon of internal residue loss from per-O-alkylated oligosaccharides, with no mechanistic explanation put forth.…”

mentioning

confidence: 99%

Evidence for long-range glycosyl transfer reactions in the gas phase

Franz

Lebrilla

2002

A long-range glycosyl transfer reaction was observed in the collision-induced dissociation Fourier transform (CID FT) mass spectra of benzylamine-labeled and 9-aminofluorene-labeled lacto-N-fucopentaose I (LNFP I) and lacto-N-difucohexaose I (LNDFH I). The transfer reaction was observed for the protonated molecules but not for the sodiated molecules. The long-range glycosyl transfer reaction involved preferentially one of the two L-fucose units in labeled LNDFH I. CID experiments with labeled LNFP I and labeled LNFP II determined the fucose with the greatest propensity for migration. Further experiments were performed to determine the final destination of the migrating fucose. , and post-translational protein modification [6 -8]. Whereas the insight into the physical process of carbohydrate recognition is in its infancy, considerable progress has been made towards the quantitation and structural elucidation of biologically active oligosaccharides. NMR [9] yields structural information about oligosaccharides. Frequently, however, an inherent problem is the limited amount of sample causing NMR experiments to become time-consuming or impossible. The sensitivity and accuracy of mass spectrometry has made this technique the best choice for analysis of oligosaccharides [10,11]. Structural information can be derived from collision-induced dissociation (CID) [12][13][14][15][16][17][18][19][20] or from post-source decay (PSD) time-of-flight (TOF) experiments [21][22][23][24][25][26]. Fragmentation of glycosidic bonds provides information about the monosaccharide sequence and computer algorithms can extract sequence information from web-based catalogs of MS n spectra [27]. However, the assignment of anomeric configuration [28 -35] and linkage [18, 36 -38] within the oligosaccharide structure is not a trivial task. Glycosidase digestion [13, 39 -47] in conjunction with mass spectrometric analysis can be used to assign linkage and stereochemistry. In an alternative approach, CID-fragmentation patterns have been linked to structural motifs in the oligosaccharide (catalog library approach) [12].We recently reported on the use of more nucleophilic benzylogous amines, such as benzylamine and 9-aminofluorene, for the labeling of oligosaccharides and the experimental results of FT-MS experiments with the labeled oligosaccharides [48]. Detection of 5 pmol of 9-amino fluorene-labeled oligosaccharide was achieved with a photo diode array during HPLC separation. The label combines low cost with good nucleophilicity and ease of introduction. The behavior of oligosaccharides derivatized with benzylogous amines such as benzylamine in CID experiments has not been reported, although data obtained from PSD matrix-assisted laser desorption/ionization (MALDI)-TOF experiments have been published [25,49].In this paper, we discuss a long-range glycosyl transfer that occurs during CID for benzylamine-and 9-AmFL-labeled oligosaccharides. The transfer of a fucose across three monosaccharide units was observed only in protonated molecules. To t...

“…Brű ll and collaborators reported that during MS/MS analysis of underivatized and per-O-methylated trisaccharides, with either high-or low-energy CID using FAB ionization, they observed losses of the internal residue of 1¡6 substituted monosaccharide [33]. This phenomenon of "internal residue loss," which was characterized as an "internal rearrangement" process catalyzed by a proton, was not observed in the CID-MS/MS analysis of sodium-cationized oligosaccharides containing N-acetyl-D-glucosamine [34].…”

Section: Discussionmentioning

confidence: 99%

“…By comparison with the work of McLafferty, Brűll, and Claeys groups [28,29,[33][34][35], our work, presented in this rationale, includes a series of amphiphilic molecules containing an amino sugar and cholesteryl moieties separated by a polyethylene spacer, which are indeed quite different from the products used in their respective rearrangements. Also the formation of the final compounds is not an O-glycoside but a C-Glycoside, the formation of which represents a formidable synthetic task to be achieved in a MS instrument.…”

Section: Discussionmentioning

confidence: 99%

Establishment of mass spectrometric fingerprints of novel synthetic cholesteryl neoglycolipids: The presence of a unique C-glycoside species during electrospray ionization and during collision-induced dissociation tandem mass spectrometry

El‐Aneed

Banoub

Koen‐Alonso

et al. 2007

In this study we evaluated the fragmentation pattern of 16 novel amphiphilic neoglycolipid cholesteryl derivatives that can be efficiently used to increase cationic liposomal stability and to enhance gene transfer ability. These neoglycolipids bear different sugar moieties, such as D-glucosamine, In addition, we observed a unique ion that could not be rationally explained by the expected fragmentation of these amphiphilic molecules. The structure of this ion was tentatively proposed with that of a C-glycoside species formed by a chemical reaction between the sugar portion and the cholesterol. MS/MS analysis of this unique [C-glycoside] ϩ confirmed the validity of the proposed structure of this ion. The presence of an amino group at position C-2 and free hydroxyl groups of the sugar motif is crucial for the formation of a "reactive" sugar oxonium ion that can form the [C-glycoside] ϩ species. In summary, we precisely established the fragmentation patterns of the tested series of neoglycolipid cholesteryl derivatives and authenticated their structure as well; moreover, we speculated on the formation of a C-glycoside with the ESI source under atmospheric pressure and in the collision cell during MS/MS analysis. (J Am Soc Mass Spectrom 2007, 18, 294 -310)