High-performance thin-layer chromatography/mass spectrometry for the analysis of neutral glycosphingolipids

This mini-review summarizes the protocol we have developed for the analysis of neutral glycosphingolipids (GSLs) by high-performance thin layer chromatography (HPTLC)-mass spectrometry (MS). We also present results obtained using this glycolipidomic approach to study neutral GSLs from mouse kidney, spleen, and small intestine. Finally, we discuss what is required for further development of this method, as well as what is expected for the future of glycolipid biology.     

Fast atom bombardment mass spectrometry of glycosphingolipids. Glycosphingolipids containing neutral sugars

Natural and synthetic glycosphingolipids containing neutral sugars have been analyzed by positive and negative ion fast atom bombardment mass spectrometry. Basic structural characterization including saccharide size and sequence and ceramide composition is possible on the basis of the fragment ions observed. The degree of fragmentation could be increased by using higher sample concentrations and lower fast atom beam energies. Commercially available synthetic compounds that had been presumed to be pure were shown to contain homologous fatty acids. Mixtures of glycosphingolipids such as those obtained from Gaucher's spleen and from human erythrocytes can be characterized and quantitated.     

Short bed-continuous development thin-layer chromatography of glycosphingolipids

The technique of short bed--continuous development chromatography has been utilized to increase the separation of glycosphingolipids on high performance thin-layer chromatography plates. The theoretical goal of increasing separation of bands by decreasing solvent strength was achieved within a practical time span as a result of the high solvent velocities in the short bed tank. Examples are given for increased separation of short and long chain neutral glycolipids, acetylated neutral glycolipids, and gangliosides.     

Low nanogram detection of nucleotides using fast atom bombardment-mass spectrometry

The effect of trimethylsilyl (TMS) derivatization on detection limits of mononucleotides in fast atom bombardment-mass spectrometry (FAB-MS) was examined. FAB-MS methods were developed to optimize sensitivity using adenosine 5'-monophosphate as a model compound and then applied to reference standards of two clinically important nucleotides: tricyclic nucleoside-5'-monophosphate (TCNMP) and 5-fluoro-2'-deoxyuridine-5'-monophosphate (FdUMP). The detection limit for the TMS derivative of TCNMP was 2.5-5 ng/microliters and less than 2.5 ng/microliters for FdUMP as its TMS derivative. This is greater than two orders of magnitude more sensitive than the FAB-MS analysis of the corresponding free compounds. These low detection limits for the TMS derivatives were obtained using a narrow scan range, signal averaging, detection in the negative ion mode, and 3-nitrobenzyl alcohol as the matrix. Hydrolysis of one or more of the labile TMS groups did occur, with the extent of hydrolysis being greatest in the more protic matrices.     

Detection of tetrodotoxin by thin-layer chromatography/fast atom bombardment mass spectrometry

A new method for detection of tetrodotoxin (TTX) by thin-layer chromatography/fast atom bombardment (FAB) mass spectrometry was developed. TTX and/or related substances were separated by TLC on LHP-K high-performance precoated plates, with a solvent system of pyridine:ethyl acetate:acetic acid:water (15:5:3:4). The plates were subjected to positive FAB mass spectrometry, under scanning within a mass range from m/z 100 to 500. TTX was identified by selected ion-monitored chromatograms at m/z 320 (M + H)+ and 302 (M + H - H2O)+, along with full scan positive ion FAB mass spectrometry. The limit of detection for TTX was about 0.1 micrograms. TTX was also detected by cellulose acetate membrane electrophoresis/FAB mass spectrometry.     

Continuous-flow fast atom bombardment-mass spectrometry of permethylated oligosaccharides: a comparative study of direct mixture analysis with packed capillary column liquid chromatography-fast atom bombardment-mass spectrometry

Conventional positive fast atom bombardment (FAB) and continuous-flow FAB analysis were carried out with permethylated lacto-N-tetraose. This latter method, a new approach, has been used to analyze a mixture of permethylated oligosaccharides by liquid chromatography-mass spectrometry (LC-MS) with a packed capillary fused-silica column and the continuous-flow probe as interface. Under these conditions, we found the continuous-flow probe to be superior to the conventional probe because its low matrix level increased the signal-to-noise ratio. The analysis of the mixture of permethylated oligosaccharide alditols obtained from hen ovomucoid by LC-MS using the continuous-flow probe as interface is described.     

Separation of neutral glycosphingolipids and sulfatides by thin-layer chromatography

Two one-dimensional systems for separation of glycolipids from total lipid extracts of tissues by thin-layer chromatography are described. System I used, as adsorbent, an alkaline mixture of silica gel without CaSO(4) binder (75%) and magnesium silicate (25%), and the lipids were "developed" with three successive solvent mixtures. The separated compounds (from the fastest to the slowest moving) were: ceramide, ceramide monohexosides, sulfatides, ceramide dihexosides, psychosine, ceramide trihexosides, and ceramide N-acetylhexosamine trihexosides. In system II a two-step development was used on an adsorbent consisting of silica gel without CaSO(4) binder (80%) and magnesium silicate (20%). The separated compounds were: ceramides, ceramide monohexosides, and ceramide dihexosides. Psychosine and sulfatides as well as ceramide trihexosides and ceramide N-acetylhexosamine trihexosides were not separated. In both systems all neutral lipids moved to the very top of the chromatogram and phospholipids stayed at the origin. Application of systems I and II for separation of glycolipids was demonstrated on total lipid extracts from animal tissues.     

Analysis of polar lipids from some representative enterobacteria, Plesiomonas and Acinetobacter by fast atom bombardment-mass spectrometry

Fast atom bombardment-mass spectrometry (FAB-MS) was used to analyse lipid extracts of bacteria to assess its usefulness for analysing anionic phospholipids of potential chemotaxonomic value. The following micro-organisms were tested: Acinetobacter calcoaceticus, Acinetobacter sp., Citrobacter freundii, Enterobacter cloacae (2 strains), Escherichia coli (3 strains), Hafnia alvei, Klebsiella oxytoca, Klebsiella pneumoniae, Morganella morganii, Plesiomonas shigelloides, Proteus mirabilis (3 strains), Serratia liquefaciens and Serratia marcescens. Negative-ion spectra provide data for twenty-seven major carboxylate anions (m/z 209–325) and for thirty-seven major phospholipid anions (m/z 645–774). Generally, the largest carboxylate peaks were due to 16: 1, 16: 0, cyc17 and 18: 1 while the largest phospholipid anion peaks were due to PE(32: 1), PE(33: 1), PE(34: 1), PE(34: 2), PG(30: 2), PG(31: 2), PG(32: 2), PG(34: 1) and PS (33: 0). However, quantitative differences were observed. For example, Acinetobacter lacked PE (33: 1) but had exceptionally high peaks at m/z 748, PS(33: 0), and m/z 281, octadecanoate. Unknown 'carboxylate' peaks were detected at m/z 254, 256, 261, 268, 282 and 301. In some cases, unknown peaks appeared to constitute possible homologous series being separated by Δ m/z of 14(≡ methylene). For chemotaxonomic purposes, the complexity of the data required numerical analysis. Using the Pearson coefficient of linear correlation, as a measure of association, it was possible to compare all strains analysed. Typical results for strain comparisons were as follows: Ent. cloacae vs Ent. cloacae, r = 0.90 ( Ent. cloacae vs Ac. calcoaceticus, r = 0.46). Thus FAB-MS represents an excellent means of obtaining large quantities of data on polar lipids of a range of bacterial isolates, which may be suitable for chemotaxonomic purposes.     

High-performance liquid affinity chromatography and in situ fluorescent labeling on thin-layer chromatography of glycosphingolipids

A method combining high-performance liquid affinity chromatography and in situ fluorescent labeling on thin-layer chromatography is introduced for determination of glycosphingolipids. Glycolipids in crude extract from rat liver were separated quantitatively from neutral lipids and phospholipids with a phenylboronic acid-derivatized silica gel column. Glycolipids were eluted quantitatively with approximately 98% of crude extract recovered. This column is useful for selective cleanup of glycosphingolipids in crude extract from tissue. Simultaneously, a fluorometric determination of glycosphingolipids with 7-amino-4-methylcoumarin after NaIO4 oxidation on a TLC plate was introduced and its condition was optimized. Glycolipids in amounts ranging from 1 to 100 pmol are easily detectable and give linear responses over the respective ranges. The method is fast and useful for the determination of glycolipids from small amounts of biological samples and requires a minimum amount of about 1 mg of biological specimen for determination of glycolipids.     

Fast atom bombardment-mass spectrometry for bacterial chemotaxonomy: influence of culture age, growth temperature, gaseous environment and extraction technique

Extracted phospholipids of Escherichia coli, Proteus mirabilis and Enterobacter cloacae were examined by fast atom bombardment-mass spectrometry which yielded major peaks between m/z 225 and 761. The result of extracting freeze-dried or 'wet' cells showed that freeze-drying may be omitted although weighing of dried cells offers a useful means of standardizing the extraction procedure. Anaerobic growth quantitatively altered the chemical finger-print as a result of increase in ratio of saturated: unsaturated carboxylic acids. Growth temperature also affected profiles over the temperature range 24–45°C. A less drastic influence on mass spectra was culture age, over the range 16–48 h. Comparison of spectra was possible with Pearson's coefficient of linear correlation which yielded the following values: wet and lyophilized cells, r = 0–97; aerobic and anaerobic growth, r = 0.82; 24°C and 45°C, Y = 0.76; 16 h and 48 h, r = 0.95. These results show that although quantitative differences do occur between spectra for the same organism prepared in different ways, they are less than interspecies variation, e.g. with E. coli and P. mirabilis, r = 0.46. Any differences which are due to preparation method can be overcome by standardization of technique.     

Analysis of polar lipids from some representative enterobacteria, Plesiomonas and Acinetobacter by fast atom bombardment-mass spectrometry.

Fast atom bombardment-mass spectrometry (FAB-MS) was used to analyse lipid extracts of bacteria to assess its usefulness for analysing anionic phospholipids of potential chemotaxonomic value. The following micro-organisms were tested: Acinetobacter calcoaceticus, Acinetobacter sp., Citrobacter freundii, Enterobacter cloacae (2 strains), Escherichia coli (3 strains), Hafnia alvei, Klebsiella oxytoca, Klebsiella pneumoniae, Morganella morganii, Plesiomonas shigelloides, Proteus mirabilis (3 strains), Serratia liquefaciens and Serratia marcescens. Negative-ion spectra provide data for twenty-seven major carboxylate anions (m/z 209-325) and for thirty-seven major phospholipid anions (m/z 645-774). Generally, the largest carboxylate peaks were due to 16:1, 16:0, cyc17 and 18:1 while the largest phospholipid anion peaks were due to PE(32:1), PE(33:1), PE(34:1), PE(34:2), PG(30:2), PG(31:2), PG(32:2), PG(34:1) and PS(33:0). However, quantitative differences were observed. For example, Acinetobacter lacked PE (33:1) but had exceptionally high peaks at m/z 748, PS(33:0), and m/z 281, octadecanoate. Unknown 'carboxylate' peaks were detected at m/z 254, 256, 261, 268, 282 and 301. In some cases, unknown peaks appeared to constitute possible homologous series being separated by delta m/z of 14(identical to methylene). For chemotaxonomic purposes, the complexity of the data required numerical analysis. Using the Pearson coefficient of linear correlation, as a measure of association, it was possible to compare all strains analysed. Typical results for strain comparisons were as follows: Ent. cloacae vs Ent. cloacae, r = 0.90 (Ent. cloacae vs Ac. calcoaceticus, r = 0.46). Thus FAB-MS represents an excellent means of obtaining large quantities of data on polar lipids of a range of bacterial isolates, which may be suitable for chemotaxonomic purposes.     

Fast atom bombardment-mass spectrometric identification of molecular species of platelet-activating factor produced by stimulated human polymorphonuclear leukocytes

Fast atom bombardment mass spectrometry was used to identify molecular species of platelet-activating factor (PAF) produced by stimulated human neutrophilic polymorphonuclear leukocytes. Normal and reverse-phase high performance liquid chromatography were employed to separate the individual regions with PAF activity prior to mass spectrometric analysis. The following alkyl chain homologs of acetyl glyceryl ether phosphorylcholine (AGEPC) were found: C16:0, C17:0, C18:0 and C18:1. There was also evidence for the presence of the C15:0 homolog, as well as other species which have not yet been identified.     

Purification and characterization of minor brain proteolipids: use of fast atom bombardment-mass spectrometry for peptide sequencing

A combination of lipophilic gel permeation chromatography and ion-exchange chromatography in organic solvents was used to purify low molecular weight proteolipids from bovine brain. Cleavage peptides were purified by HPLC and studied mainly by the fast atom bombardment--mass spectrometry technique. A proteolipid of Mr 14 000 contains several peptides from the first 113 amino acids of the major myelin proteolipid (MMPL) plus an extra unknown blocked N-terminal peptide. A proteolipid of Mr 16 000 contains smaller peptides belonging to a C-terminal fragment of MMPL of about 160 residues. These two proteolipids do not seem to be artifacts from MMPL.     

Fast atom bombardment mass spectrometry of bovine proinsulin

The application of Fast Atom Bombardment Mass Spectrometry to the measurement of small differences in molecular weight is discussed in relation to the spectra of bovine proinsulin and a genetic variant.     

Fast atom bombardment mass spectrometry of human proinsulin

The observation of protonated molecular species from human proinsulin obtained by fast atom bombardment mass spectrometry is reported.     

Purification and characterization of low-molecular-weight beef heart proteolipids: use of fast atom bombardment-mass spectrometry for identification

Bovine cardiac muscle was extracted by an acidic chloroform/methanol mixture. A combination of gel permeation and ion-exchange chromatographies in organic solvents and HPLC allowed the purification of subunits VIIIa (Mr 5400) and VIIIb (Mr 4900) of cytochrome c oxidase and of A6L protein (Mr 7900) of ATP synthase. The identification of the proteins was made possible by measurement of their molecular weight by fast atom bombardment-mass spectrometry (FAB-MS) in conjunction with conventional Edman degradation. The determination by FAB-MS of the molecular weight of A6L protein confirmed its supposed formylated N-terminal methionine.     

N-glycosylation site mapping of human serotransferrin by serial lectin affinity chromatography, fast atom bombardment-mass spectrometry, and 1H nuclear magnetic resonance spectroscopy.

This report describes the N-glycosylation site mapping of human serotransferrin (h-STF). Reduced and S-carboxymethylated h-STF was digested with trypsin or chymotrypsin. Glycopeptides in the proteolytic digests were isolated by serial concanavalin A (Con A), Sambucus nigra agglutinin (SNA), and Phaseolus vulgaris leukoagglutinin (LPHA) affinity chromatography and subjected to preliminary analysis by 1H NMR spectroscopy. The glycopeptide fractions were then individually digested with N-glycanase. One part of the digest of each fraction was analyzed by fast atom bombardment-mass spectrometry (FAB-MS) to identify the peptide sequences of the glycosylation sites. The other part was used to isolate the oligosaccharide by the corresponding lectin affinity chromatography and to characterize the structures of the isolated oligosaccharides by 1H NMR spectroscopy and FAB-MS. The oligosaccharides in the Con A-bound fraction were shown to have bi-alpha(2-->6)-sialyl, diantennary structures. The SNA-bound fraction was shown to contain trisialyl, triantennary structures. Di- and triantennary oligosaccharides were found to occur on each of the two N-glycosylation sites of h-STF (Asn413 and Asn611) in the ratio of approximately 85:15. The SNA-bound glycopeptides were further fractionated by LPHA affinity chromatography. Two different oligosaccharides were characterized, namely, a trisialyl 2,4-triantennary and a trisialyl 2,6-triantennary glycan. The ratio of 2,4-triantennary vs 2,6-triantennary oligosaccharides attached to glycosylation site Asn413 was found to be approximately 5:1, whereas the two isomeric triantennary oligosaccharides were found to be attached to glycosylation site Asn611 in the ratio approximately 1:1.     

Structural definition of the non-reducing termini of mannose-capped LAM from Mycobacterium tuberculosis through selective enzymatic degradation and fast atom bombardment-mass spectrometry

The application of extracellular arabinases from aCellulomonassp. and fast atom bombardment-mass spectrometry (FAB-MS) providednew insight into the structure of lipoarabinomannan (LAM) ofMycobacterium tuberculosis, a key molecule in the pathogenesisand physiology of the tubercle bacillus. Previously, the non-reducingarabinan ends of LAM from the virulent (Erdman) strain of M.tuberculosiswere shown to be ‘capped’ by short (a1     

A rapid preparative method for isolation of neutral and acidic glycosphingolipids by radial thin-layer chromatography

An efficient method to separate neutral and acidic glycosphingolipids (GSLs) from their mixtures within a short period (45-60 min) and with low consumption of solvents (chloroform-methanol-water, 60/35/8 (v/v/v); 250-500 ml) has been developed. This method utilizes a centrifugal thin-layer chromatograph (Chromatotron) and the GSL mixtures (30-400 mg) are applied to glass plates coated with a 1-mm layer of silica gel 60 PF-254. The method (radial thin-layer chromatography) is rapid and simple and the recovery of glycosphingolipids is high (70-80%).