Sequential mass spectrometry of saccharides: Identification of 2‐deoxy‐2‐aminohexose stereoisomers in glycoconjugates

Abstract

Mass spectrometric methods for the identification of hexose stereoisomers in glycoconjugates have recently beenThe relative abundance "fingerprints" of the products of collision induced dissocation (CID) were found to be characteristic of the isomeric sugars, and can be used for unambiguous identification of hexose residues in complex molecules. Sequential collision mass spectrometry experiments (MSlMS and MSIMSIMS) were shown to be useful for investigation of the CID reactions of the hexose stereoisomers.3Mass spectrometry with electron ionization (EI), chemical ionization (CI), and fast atom bombardment ionization (FAB) have been used for the identification of acetylated 2-deoxy-2-amino saccharide^.^.^ In this report we describe the application of sequential collision mass spectrometry to the identification of acetylated stereoisometric amino sugars. In addition, MSIMSIMS results are presented for several ions derived from peracetylated glucosamine, galactosamine and mannosamine. Instrumentation and Operating ConditionsMass spectra were acquired with a ZAB-EQ hybrid instrument manufactured by VG Analytical Ltd. (ManChester, UK). Collision induced dissociation experiments may be carried out at high energy in the first or second field free region (FFR) or at low energy in an R F only quadrupole after deceleration of the ion beam. Details of the instrumentation have been described elsewhere." The mass spectrometer was operated with a source potential of 8 kV. Helium gas pressure in the cell in the second FFR was adjusted to attenuate the ion beam by 25 %. The pressure of argon collision gas in the RF-only quadrupole was adjusted to attenuate the ion beam by 50 YO. The quadrupoles were floated near 8 kV, adjusted so that ions entering the RF-only quadrupole collision cell had 50 eV energy. Several sequential collision experiments are possible with a hybrid mass ~pectrometer,~ but the MS/MS/MS experiments described in this report are a sequential combination of collisions in the second FFR (to yield a daughter ion) followed by collisions in the RF-only quadrupole (to yield a granddaughter ion).Thioglycerol matrix was used for the FAB experiments. Between 1 and 5 p L of sample solution was delivered to the FAB probe tip, and the solvent Author to whom correspondence should be addressed of thioglycerol matrix was added with a platinum wire. The FAB gun was operated using xenon, at 8kV and 1 mA current. N-acetyl-D-glucosamine, N-acetyl-ogalactosamine and N-acetyl-D-mannosamine were obtained from Pfanstiehl Laboratories (Waukegan, The reproducibility of daughter spectra of the acetylated amino sugars was evaluated with five replicate MSiMS experiments performed on each of glucosamine and galactosamine. The five measurements on each sugar were interleaved with those on the other sugar and the FAB probe tip cleaned with water between samples. The ratio of abundance of ions of m/z 150 to 168 in the daughter spectra of ions of nzlz 330 was 2.5450.06 for acetylated glucosamine and 1.51 rfr0.04 for acetylated galactosamine.Th...

Unimolecular and collision‐induced dissociation reactions of peracetylated methyl glucopyranoside

“…M211 to an M109 fragment is not observed in MS/MS/ MS experiments (Table 2), and consequently the abundance of Ac24 is taken to be low, and approximate 96% = a(Ac246) + ~(Ac346) 4% = a(Ac234) + a(Ac236) (from 3b) (7) abundances for the predominant species calculated A simple structure b, (Ac46) is inconsistent with rea-(from 3b) (8) (Fig. 2).…”

Coordination of Alkali Metals to Oligosaccharides Dictates Fragmentation Behavior in Matrix Assisted Laser Desorption Ionization/Fourier Transform Mass Spectrometry

“…Mass spectrometry specifically with fast atom bombardment (FAB) and liquid secondary ion mass spectrometry (LSIMS) ionization methods have been extensively used to analyze oligosaccharides. The application and limitations of these two similar techniques are well-known and have been illustrated in several review and key articles. − Their major limitation is the relatively poor detection limit. Laser desorption, with and without, matrix has been more recently developed but has been used already with great success to analyze carbohydrate structures.…”

Collision-Induced Dissociation of Branched Oligosaccharide Ions with Analysis and Calculation of Relative Dissociation Thresholds

“…Nuclear magnetic resonance (NMR) spectroscopy can give very detailed structural information, but interpretation of the data for complex oligosaccharides is not trivial, and milligram quantities of pure material are often needed for complex two-dimensional experiments − Electrospray ionization (ESI) is another ionization technique amenable to oligosaccharides. Reinhold et al have reported ESI of methylated glycosphingolipids and have successfully carried out collision-induced dissociation (CID) .…”