Oligosaccharide sequence determination using B/E linked field scanning or tandem mass spectrometry of phosphatidylethanolamine derivatives

Product ion mass spectral data of [M + H]+ ions of oligosaccharides, mainly tetra- and pentasaccharides, as their dipalmitoyl phosphatidylethanolamine derivatives were obtained using both liquid secondary ion mass spectrometry with B/E linked scanning and fast atom bombardment ionization with collision-induced dissociation/tandem mass spectrometry. Both methods give similar positive product ion spectra of equivalent high sensitivity (detection limits of approximately 50 pmol) that principally contain glycosidic cleavage ions retaining the reducing end of the molecule from which monosaccharide sequence can be deduced. A series of ions from fission of the phosphate ester bond together with glycosidic cleavage are present in the tandem mass spectra and B/E linked scan spectra when helium collision gas is used. Monosaccharide linkage position of isomeric molecules is reflected in the intensity of glycosidic fragmentation, without retention of the oxygen atom, with decreasing cleavage in the order 1-3 greater than 1-4 greater than 1-6 linkage. Fucose and N-acetylhexosamines show an increased degree of fragmentation over hexose sugars. The application of product ion spectra of derivatized oligosaccharides is demonstrated for characterizing mixed samples and also the acquisition of spectra directly from the silica surface of high-performance thin-layer chromatography plates.

Identification of peroxyacetic acid uroporphyrin I in the urine of patients with congenital erythropoietic porphyria by liquid chromatography and mass spectrometry

A new porphyrin, peroxyacetic acid uroporphyrin I, has been isolated from the urine of patients with congenital erythropoietic porphyria by reversed phase high performance liquid chromatography. The porphyrin was characterized by high resolution mass spectrometry and by typical chemical reactions of a peroxyacid.

Enzyme degradation, high performance liquid chromatography and liquid secondary ion mass spectrometry in the analysis of glycoproteins

Analysis of small amounts of glycoproteins by high performance liquid chromatography (HPLC) and liquid secondary ion mass spectrometry (LSIMS) together with enzyme digestion has been investigated using fetuin as a model. Preliminary data indicates that 71% of the expected peptides were detected by LSIMS analysis of 200 pmol total digest. HPLC profiles of peptides and glycopeptides were obtained from 2 nmol of digest using a reversed phase (C18) column eluted in a solvent system containing TFA, water and acetonitrile. This has provided glycopeptides for subsequent oligosaccharide analysis. Strategies are reviewed for the chromatographic characterization of oligosaccharides following their release from glycopeptides by chemical and enzymatic procedures.

Isolation and characterization of beta-hydroxypropionic acid- and hydroxyacetic acid-uroporphyrin I in the urine of a patient with congenital erythropoietic porphyria by high performance liquid chromatography and liquid secondary ion mass spectrometry

beta-Hydroxypropionic acid- and hydroxyacetic acid-uroporphyrin I have been isolated from the urine of a patient with congenital erythropoietic porphyria by reversed phase high performance liquid chromatography. The compounds were characterized by their chemical behaviour and confirmed by liquid secondary ion mass spectrometry.

Microscale sequencing of O-linked oligosaccharides using mild periodate oxidation of alditols, coupling to phospholipid and TLC-MS analysis of the resulting neoglycolipids

In the course of characterising neoglycolipid products derived from mucin oligosaccharide alditols after periodate oxidation and coupling by reductive amination to the aminolipid dipalmitoylglycerophosphoethanolamine, we have obtained evidence that oxidative cleavage occurs specifically at the C4-C5 bond of core N-acetylgalactosaminitol. Two lipid-linked fragments thus obtained from each oligosaccharide alditol are well resolved on thin-layer chromatography and can be sensitively analysed by liquid-secondary-ion mass spectrometry to assign the sequence and branching patterns of oligosaccharides linked at C6 and C3 to the N-acetylgalactosamitol. These conclusions have been reached from detailed studies of the neoglycolipid derivatives of several oligosaccharides (di- to hexasaccharides) which were isolated from human meconium and characterised previously by MS and NMR studies as the free alditols.

High-sensitivity structural analyses of oligosaccharide probes (neoglycolipids) by liquid-secondary-ion mass spectrometry

The sensitivity of detection and extent of information on structure obtainable by liquid-secondary-ion mass spectrometry (l.s.i.-m.s.) of neoglycolipids on the conventional target probe and directly from the surface of silica plates following t.l.c. has been assessed. Neoglycolipids were derived from malto-oligosaccharides, chitin oligosaccharides, and a range of deoxyhexose-, hexose-, 2-acetamido-2-deoxyhexose-, and sialic acid-containing mammalian oligosaccharides by reductive amination using phosphatidylethanolamine dipalmitoate (PPEADP). Sub-pmol amounts of the maltopentaose-PPEADP derivative applied directly to the target probe provided information on molecular weight, whereas approximately 1 pmol was required when analysed on the silica gel t.l.c. plate. With a biantennary octasaccharide derivative, the sensitivity of detection was 20-50 times lower and the other oligosaccharides had intermediate sensitivities. Information on composition and sequence was obtained readily from fragment ions, using 5 pmol of the maltopentaose derivative and 50 pmol of the octasaccharide derivative on the target probe, and 50 and 200 pmol, respectively, on the silica gel chromatogram. The optimised conditions formed the basis for characterising the structures of the components of mixtures of oligosaccharides generated from glycoproteins.

Bile acid profiles in peroxisomal 3-oxoacyl-coenzyme A thiolase deficiency

Fast atom bombardment mass spectrometry and gas chromatography-mass spectrometry were used to analyze bile acids in the body fluids of an infant (L.C.) whose liver contained no immunoreactive peroxisomal 3-oxoacyl-CoA thiolase. The profiles were compared with those of six patients with undetectable peroxisomes (Zellweger syndrome) and two siblings (N.B. and I.B.) whose defect of peroxisomal beta-oxidation could not be localized by morphological studies of peroxisomes or by immunoblotting of peroxisomal beta-oxidation proteins. 3 alpha, 7 alpha, 12 alpha-Trihydroxy-5 beta-cholestan-26-oic acid (THCA) was present in bile and plasma of all patients. However, bile from L.C., N.B. and I.B. contained unconjugated varanic acid (3 alpha, 7 alpha, 12 alpha, 24-tetrahydroxy-5 beta-cholestan-26-oic acid) as the major C27 bile acid, whereas bile from Zellweger patients contained only small amounts of varanic acid. In the bile from L.C. two isomers of varanic acid were present; in the bile from N.B. and I.B. a single isomer predominated. L.C., N.B., and I.B. all produced bile containing small amounts of (24E)-3 alpha, 7 alpha, 12 alpha-trihydroxy-5 beta-cholest-24-en-26-oic acid [( 24E]-delta 24-THCA), its [24Z]- isomer, 3 alpha, 7 alpha, 12 alpha-trihydroxy-5 beta-cholest-23-en-26-oic acid and 3 alpha, 7 alpha, 12 alpha-trihydroxy-27-nor-5 beta-cholestan-24-one. The results provide evidence for peroxisomal pathways for cholic acid synthesis in man via THCA, delta 24-THCA and varanic acid and show that bile acid analyses can be used to diagnose peroxisomal thiolase deficiency.

Characterisation by mass spectrometry and 500-MHz proton nuclear magnetic resonance spectroscopy of penta- and hexasaccharide chains of human foetal gastrointestinal mucins (meconium glycoproteins)

Structural studies using liquid secondary ion mass spectrometry, gas liquid chromatography/mass spectrometry and 500-MHz 1H NMR are described of the major penta- and hexasaccharides of a fraction of human foetal gastrointestinal mucins. Glycoproteins from a blood group H active meconium pool were studied after depletion of Ii antigenic activities by immunoaffinity chromatography and treatment with mild acid hydrolysis to reduce the chain heterogeneity. Oligosaccharides were released by mild alkali/borohydride degradation and purified by Bio-Gel P4 chromatography and HPLC. Eleven penta- and hexasaccharides have been fully characterised as a result of this study and one previous report [Hounsell et al. (1988) Biochem. J. 256, 397-401] and information obtained on additional oligosaccharides present in small amounts. These oligosaccharides show the following features: (table; see text) Sequences in these oligosaccharides not commonly found in mucins so far studied are chain-terminating GlcNAc alpha 1-4Gal, repeating-type-I (Gal beta 1-3GlcNAc) backbones, the backbone branch GlcNAc beta 1-6(GlcNAc beta 1-3)Gal and the backbone sequence GlcNAc beta 1-6Gal beta 1- in the absence of a substituent at C3 of galactose.

Oligosaccharide-mediated interactions of the envelope glycoprotein gp120 of HIV-1 that are independent of CD4 recognition

In this study carbohydrate-mediated interactions of the envelope glycoprotein, gp120, of HIV-1 were investigated. Oligosaccharide probes (neoglycolipids), prepared from the N-glycosidically-linked chains of the natural and recombinant forms of gp120, were used in conjunction with the intact glycoprotein to investigate reactivities with a soluble carbohydrate-binding protein (lectin) known as mannose-binding protein in human serum. Evidence is presented that the high-mannose-type oligosaccharides with seven, eight and nine mannose residues from both forms of gp120 are recognized by the serum lectin, and that these reactivities are unrelated to CD4 recognition. Reactivities of the two forms of envelope glycoprotein with macrophages derived from human blood monocytes and with the mannose-specific macrophage endocytosis receptor isolated from human placental membranes were also investigated. Evidence is presented that both forms of gp120 bind to the macrophage surface by multiple interactions in addition to CD4 binding, and that among these interactions is a carbohydrate-mediated binding to the endocytosis receptor. We propose that such carbohydrate-mediated interactions could form the basis of viral attachment to a variety of healthy and diseased tissues.

A library of oligosaccharide probes (neoglycolipids) from N-glycosylated proteins reveals that conglutinin binds to certain complex-type as well as high mannose-type oligosaccharide chains

This report describes the preparation of a library of oligosaccharide probes (neoglycolipids) from N-glycosylated proteins, characterization of the probes by liquid secondary ion mass spectrometry, and investigation of their reactions with 125I-labeled bovine serum conglutinin by chromatogram binding assays. The results, together with additional binding studies using neoglycolipids derived from purified complex type bi-, tri-, and tetraantennary oligosaccharides from urine, or their glycosidase-treated products, have shown that the combining specificity of conglutinin includes structures not only on high mannose-type oligosaccharides but also on hybrid- and complex-type chains. With high mannose-type oligosaccharides there is increased reactivity from the Man5 to the Man8 structures, indicating a preference for the terminal Man alpha 1-2 sequence. With complex- and hybrid-type oligosaccharides, the requirements for binding are the presence of nonreducing terminal N-acetylglucosamine or mannose residues, but the presence of a bisecting N-acetylglucosamine residue may inhibit binding. From these results it is deduced that the reactivity of conglutinin with the complement glycopeptide iC3b rather than the intact glycoprotein C3 is due to the oligosaccharide accessibility rendered by proteolysis in the complement cascade.

Structural heterogeneity among unique sulfated L-galactans from different species of ascidians (tunicates)

The sulfated polysaccharides that occur in the tunic of ascidians differ markedly in molecular weight and chemical composition. A high molecular weight fraction (F-1), which has a high galactose content and a strong negative optical rotation, is present in all species. Several structural differences were observed among the F-1 fractions obtained from three species of ascidians that were studied in detail. Large numbers of alpha-L-galactopyranose residues sulfated at position 3 and linked glycosidically through position 1----4 are present in F-1 from all three ascidians. However, alpha-L-galactopyranose units, 1----3-linked and partially sulfated at position 4, comprise about half of the sugar units in the central core of F-1 from Ascidian nigra. In addition, L-galactopyranose nonreducing end units occur in F-1 from Styela plicata and A. nigra, but comprise only a minor fraction of F-1 from Clavelina sp. The combination of these various component units gives a complex structure for F-1 from S. plicata and A. nigra, whereas F-1 from Clavelina sp. possesses a simpler structure. The structures of these ascidian glycans are unique among all previously described sulfated polysaccharides, since they are highly branched (except that from Clavelina sp), sulfated at position 3, and contain large amounts of L-galactose without its D-enantiomorph. These data show unusual examples of polyanionic glycans with structural function in animal tissues.

Identification of a novel oligosaccharide backbone structure with a galactose residue monosubstituted at C-6 in human foetal gastrointestinal mucins

An oligosaccharide purified from a major penta- to hexa-saccharide fraction of human meconium glycoproteins has been shown by m.s. and n.m.r. analysis to have a novel backbone structure containing an internal galactose residue monosubstituted at C-6 by N-acetylglucosamine: (Formula: see text). This oligosaccharide may represent a biosynthetic product of a previously unrecognized N-acetylglucosaminyltransferase catalysing formation of a linear GlcNAc beta 1-6Gal sequence.

Tentative identification of a digoxin-like immunoreactive substance

Three independent immunoassays gave significantly different results when digoxin concentrations were measured in plasma samples from a 68-year-old male patient with renal and liver impairment. These differences were used to provide a means of isolating a digoxin-like immunoreactive substance (DLIS) by high-pressure liquid chromatography. Examination of this fraction by fast atom bombardment-mass spectrometry provided data to support the hypothesis that excess bile acids might be the source of the DLIS in our patient which may also explain the DLIS observed in neonates.

Characterisation of oligosaccharides released from human-blood-group O erythrocyte glycopeptides by the endo-beta-galactosidase of Bacteroides fragilis. A study of the enzyme susceptibility of branched poly(N-acetyllactosamine) structures

Desialylated human blood group O erythrocyte glycopeptides were digested with the endo-beta-galactosidase of Bacteroides fragilis and the enzyme-released products reduced with NaBH4 and purified by Bio-Gel P-4 chromatography. Three linear and six branched oligosaccharides of poly(N-acetylllactosamine) type, which together accounted for 90% of the oligosaccharide alditols, were characterised by fast-atom-bombardment mass spectrometry and gas-liquid chromatography/mass spectrometry. Linkage and composition data were obtained for the remaining material. The salient findings were (a) the branched oligosaccharide alditols each contained the sequence: (Formula: see text) and (b) there was no evidence for the terminal branch-point sequence: (Formula: see text). Together these observations indicate that, as with erythrocyte glycolipids described previously [Scudder, P., Hanfland, P., Uemura, K. & Feizi, T. (1984) J. Biol. Chem. 259, 6586-6592], the endo-beta-galactosidase of Bacteroides fragilis cannot hydrolyse branch-point beta-galactosidic linkages on erythrocyte membrane glycopeptides.

Familial giant cell hepatitis associated with synthesis of 3 beta, 7 alpha-dihydroxy-and 3 beta,7 alpha, 12 alpha-trihydroxy-5-cholenoic acids

Urinary bile acids from a 3-mo-old boy with cholestatic jaundice were analyzed by ion exchange chromatography and gas chromatography-mass spectrometry (GC-MS). This suggested the presence of labile sulfated cholenoic acids with an allylic hydroxyl group, a conclusion supported by analysis using fast atom bombardment mass spectrometry (FAB-MS). The compounds detected by FAB-MS were separated by thin layer chromatography and high performance liquid chromatography. The sulfated bile acids could be solvolyzed in acidified tetrahydrofuran, and glycine conjugates were partially hydrolyzed by cholylglycine hydrolase. Following solvolysis, deconjugation, and methylation with diazomethane, the bile acids were identified by GC-MS of trimethylsilyl derivatives. The major bile acids in the urine were 3 beta,7 alpha-dihydroxy-5-cholenoic acid 3-sulfate, 3 beta,7 alpha,12 alpha-trihydroxy-5-cholenoic acid monosulfate, and their glycine conjugates. Chenodeoxycholic acid and cholic acid were undetectable in urine and plasma. The family pedigree suggested that abnormal bile acid synthesis was an autosomal recessive condition leading to cirrhosis in early childhood.

Plasma bile acids in patients with peroxisomal dysfunction syndromes: analysis by capillary gas chromatography-mass spectrometry

Six patients with disorders of peroxisomal function have been studied. Two presented in the neonatal period with the classical features of the Zellweger syndrome, two had incomplete Zellweger phenotypes, one infantile Refsum's disease and one rhizomelic chondrodysplasia punctata. Plasma bile acid profiles were determined using capillary gas chromatography-mass spectrometry. In all patients, except the case of chondrodysplasia punctata, 27-carbon and 29-carbon bile acids were present. The compounds identified included trihydroxycoprostanic acid (THCA), dihydroxycoprostanic acid (DHCA), C24-, C25- and C26-hydroxylated derivatives of THCA, a 27-carbon acid with four nuclear hydroxy groups and 3 alpha,7 alpha,12 alpha-trihydroxy-27a,27b-dihomo-5 beta-cholestan-26, 27b-dioic acid (C29-dicarboxylic acid). THCA was present at a low concentration in the patient with infantile Refsum's disease; the concentration of DHCA and the C29 dicarboxylic acid were considerably higher. The presence of abnormal bile acids in patients with Zellweger syndrome and infantile Refsum's disease could be explained by the absence of peroxisomes from their hepatocytes. In chondrodysplasia punctata the cause of peroxisomal dysfunction must be different, since normal bile acid synthesis is preserved.

On the homogeneity of stools with respect to bile acid composition and normal day-to-day variations: a detailed qualitative and quantitative study using capillary column gas chromatography-mass spectrometry

Fecal bile acid excretion was determined using recently developed techniques in order to investigate: the extent of the homogeneity in composition and concentration of individual bile acids in a single stool sample, the detailed qualitative and quantitative day-to-day variations in total and individual bile acids in the typical healthy adult, information on the relative proportions of conjugated bile acids in healthy stools, and inter-individual variations in fecal bile acid excretion. Bile acids were extracted from feces and separated into groups based upon their mode of conjugation using lipophilic gel chromatography, prior to analysis by capillary column gas chromatography-mass spectrometry. The majority of bile acids were excreted in the unconjugated form, while in all samples, conjugated bile acids accounted for less than 6% of the total fecal bile acids excreted, of which sulphated bile acids represented less than 3% of the total. Quantitative total and individual bile acid excretion, determined from single daily collections exhibited wide variations in values from day-to-day, and in accordance with early findings, indicates the need to use a minimum of 3- to 5-day collections for a more reliable index of bile acid excretion in feces. Examination of frozen and sectioned single stools revealed wide variations in water content and in quantitative bile acid concentration and composition within the stool. These data indicate random stool samples, which are commonly used in clinical studies, and data expressed as concentrations to be unsatisfactory for the accurate determination of fecal bile acid excretion.

Rapid diagnosis of Zellweger syndrome and infantile Refsum's disease by fast atom bombardment--mass spectrometry of urine bile salts

A method is described for the rapid determination of urinary bile salt profiles by fast atom bombardment--mass spectrometry (FAB-MS). Urine was passed through a reverse-phase octadecylsilane bonded silica cartridge and the bile salts eluted with methanol. Negative ion FAB spectra could be obtained from the equivalent of 10 microliter of urine loaded onto the target probe with glycerol as matrix. In samples from normal infants and children bile salt peaks were rarely detectable above the background whereas peaks produced by steroid sulphates and glucuronides and bile alcohol glucuronides could usually be identified. In samples from infants and children with cholestasis the major peaks were produced by the taurine and glycine conjugates of di-, tri- and tetrahydroxycholanoic acids (and their monosulphates). In samples from patients with Zellweger syndrome and infantile Refsum's disease, a unique ion at m/z 572 indicated the presence of taurine-conjugated tetrahydroxy-cholestanoic acid(s). The amide linkage to taurine was cleaved by alkaline hydrolysis but not by cholylglycine hydrolase. Capillary gas chromatography--mass spectrometry (GC-MS) of the bile acids liberated by alkaline hydrolysis indicated the presence of at least two nuclear-tetrahydroxylated cholestanoic acids, probably the 6 alpha- and 1 beta-hydroxylated derivatives of 3 alpha, 7 alpha, 12 alpha-trihydroxy-5 beta-cholestan-26-oic acid.

Detailed faecal bile acid profile: a diagnostic test for colorectal cancer?

Detailed profiles of bile acids in faeces were evaluated as a diagnostic test for colorectal cancer in rats. Twenty-seven bile acid peaks were measured using improved methods of extraction and separation followed by the sensitive and specific techniques of capillary column gas liquid chromatography and mass spectrometry. Colorectal cancer was induced in experimental animals (female Sprague-Dawley rats, n = 20) by subcutaneous injection of dimethylhydrazine (DMH) and faecal unconjugated bile acids compared with those in the control group (n = 20). The amount of total faecal unconjugated bile acids was lower in the animals administered DMH (255 mg/day vs 334 mg/day: (P = 0.04), and the excretion of seven individual bile acids was reduced when compared with those in the control group (P less than 0.01). In order to use the faecal bile acid profiles as a diagnostic test, linear discriminant analysis was performed. A discriminant score was derived which was applied to each profile, to determine to which group (control or DMH) each animal belonged retrospectively. All analyses were performed blind, and 90% of the animals were correctly assigned. In man, as in rats, the bile acid profile of faces is equally complex and the bile acid profile may be useful as a diagnostic test.

Isolation and characterization of sulphated oligosaccharides released from bovine corneal keratan sulphate by the action of endo-beta-galactosidase

A series of oligosaccharides has been isolated from the keratan sulphate peptidoglycan (3 M NaCl fraction) of bovine cornea after digestion with the endo-beta-galactosidase of Bacteroides fragilis. Structural information on the major oligosaccharides was obtained from (a) their susceptibilities to endo-beta-galactosidase before and after desulphation, (b) their elution positions on a column of Bio-Gel P-4 and retention times on a high-performance anion-exchange column and (c) negative-ion fast-atom-bombardment mass spectrometry. More than 75% of the oligosaccharides were sulphated unbranched poly(N-acetyllactosamine) sequences, (-3/4GlcNAc beta 1-3Gal beta 1-)n, and approximately 3% was the neutral disaccharide, GlcNAc beta 1-3Gal. The sulphated disaccharide, GlcNAc-SO-3 beta 1-3Gal, accounted for almost 35% of the oligosaccharide material while 40% consisted of four oligosaccharides, unbranched tetra-, hexa-, octa- and decasaccharides of poly(N-acetyllactosamine) type, having 3, 5, 7 and 9 sulphate residues respectively. Proton nuclear magnetic resonance studies at 500 MHz (Hounsell, E. F., et al. following paper in this journal) have shown that a sulphate residue is attached to the C-6 position of each N-acetylglucosamine and each internal galactose residue of these four oligosaccharides which express to varying degrees the antigenic determinants recognised by three monoclonal antibodies to keratan sulphate (Mehmet, H. et al., paper which follows the next paper in this journal).

Analysis of tumour-localizing haematoporphyrin derivative by high-performance liquid chromatography and fast-atom bombardment mass spectrometry

Reversed-phase chromatography using a MOS-Hypersil (C8) column with methanol-1 M ammonium acetate buffer (pH 4.6) (60:40) as mobile phase has been developed for the isolation of tumour-localizing haematoporphyrin derivative (HPD). The system effectively resolved the diastereoisomers of haematoporphyrin and its acetyl derivatives. The chromatography peaks were identified by fast-atom bombardment mass spectrometry and were confirmed by chemical synthesis. The main components of HPD before alkaline hydrolysis were diacetylhaematoporphyrin, 8-(1-acetoxyethyl)haematoporphyrin and 3-(1-acetoxyethyl)haematoporphyrin with small amounts of haematoporphyrin, 8-(1-hydroxyethyl)-3-vinyldeuteroporphyrin, 3-(1-hydroxyethyl)-8-vinyldeuteroporphyrin, 8-(1-acetoxyethyl)-3-vinyldeuteroporphyrin, 3-(1-acetoxyethyl)-8-vinyldeuteroporphyrin and protoporphyrin. After hydrolysis with 0.1 M sodium hydroxide, the main components were haematoporphyrin, hydroxyethylvinyldeuteroporphyrins, and protoporphyrin.

Glycerol-3-phosphate excretion in fructose-1,6-diphosphatase deficiency

A patient aged 23 months with fructose-1,6-diphosphatase deficiency is reported. This infant demonstrated an increased urine excretion of glycerol-3-phosphate during episodes of hypoglycaemia. The excretion of this compound has not previously been described in this disease or in those disorders associated with a deficiency in one of the other three gluconeogenic enzymes associated with hypoglycaemia. Its presence in the urine from patients may be useful in diagnosis.

Structural analysis of the O-glycosidically linked core-region oligosaccharides of human meconium glycoproteins which express oncofoetal antigens

Glycoproteins were extracted from meconium samples of group O neonates of secretor type by pronase digestion followed by precipitation in 67% aqueous ethanol and separated into Ii antigen enriched and depleted fractions by affinity chromatography. The latter fraction strongly expressed the oncofoetal antigens recognised by natural antibodies in mouse sera and the hybridoma antibody FC 10.2, and this activity was enhanced after mild acid hydrolysis to remove sialic acid and fucose residues. Oligosaccharides were released from the mild-acid-treated fraction by base-borohydride degradation and purified by gel permeation chromatography on Bio-Gel P4 and high performance liquid chromatography on octadecylsilyl and aminopropylsilyl columns. The major oligosaccharides were characterised by fast atom bombardment and electron impact mass spectrometry, combined gas-liquid chromatography/mass spectrometry and 500-MHz proton NMR spectroscopy. Their structures, in order of abundance, were: (Formula: see text).

Production and metabolism of lignans by the human faecal flora

Lignans have, until recently, been found only in plants. Enterolactone and enterodiol are the major lignans present in the urine of humans and have a potential physiological protective role against cancer. It has been shown that these compounds can be formed in vitro by human faecal flora and that enterodiol is oxidized to enterolactone by bacteria that are present in stools at a concentration of up to 10(3)/g. It was also possible to produce both of these lignans in vitro from linseeds and from secoisolariciresinol, a precursor present in linseed, by bacteria present in stools, at a concentration of between 10(3) and 10(4)/g. Enterolactone was produced from matairesinol, a more abundant plant lignan than secoisolariciresinol, after incubation with a mixed faecal flora under both aerobic and anaerobic conditions. In each case conversion was dependent on the presence of viable bacteria. These findings indicate that a number of different pathways operate to produce enterolactone and enterodiol depending on the ingested dietary precursor.

Fast-atom-bombardment mass spectrometry and electron-impact direct-probe mass spectrometry in the structural analysis of oligosaccharides with special reference to the poly(N-acetyl-lactosamine) series

A comparison has been made of positive- and negative-ion fast-atom-bombardment (FAB) and electron-impact (EI) mass spectrometry for analysis of oligosaccharides and alditols containing alternating and consecutive sequences of neutral and acetamido sugars. Among these were novel chemically synthesized tetrasaccharides with Ii antigen activities. FAB ionization has the advantage that it is applicable to non-derivatized oligosaccharides and it can determine Mr. However, the abundance of fragment ions providing structural information and the amount of material required for analysis (1-50 nmol) varied from sample to sample. In contrast, EI mass spectrometry of 5 nmol of permethylated or peracetylated oligosaccharides reliably gives all the fragment ions formed by cleavage across the glycosidic bonds.

The effect of mild alkali and alkaline borohydride on the carbohydrate and peptide moieties of fetuin

In the light of recent reports, based on radioactive labelling studies, that substantial amounts of N-linked oligosaccharides are released from protein under the mild-alkaline borohydride degradation conditions that are usually used to release O-linked oligosaccharides, we have investigated by chemical methods the effects of alkali alone and alkaline borohydride on the carbohydrate and peptide moieties of fetuin. The chromatographic profiles on Sephadex G50 columns, of the hexose- and ninhydrin-positive components of the native and Pronase-treated glycoprotein have been compared with those obtained after treatment with mild alkali alone (0.05 M-NaOH, 50 degrees C, 16 h) or mild-alkaline borohydride (0.05 M-NaOH containing 1 M-NaBH4, 50 degrees C, 16 h). Composition and methylation analyses have been performed on carbohydrate-containing peaks and the following conclusions were drawn: mild alkali treatment alone liberated a minor hexose- and ninhydrin-positive component and mild-alkaline borohydride treatment gave a major hexose-containing peak: both of these co-chromatographed on a Sephadex G50 column with Pronase glycopeptides. The polypeptide backbone was totally broken down by the alkaline borohydride treatment. The presence of released N-linked chains after alkaline borohydride treatment was confirmed. However, from the carbohydrate composition it was calculated that no more than 10-20% of the N-linked chains were released from protein. The results of methylation analysis have raised the possibility that this release is in part due to cleavage of the chitobiosyl core.

Identification of a diene conjugated component of human lipid as octadeca-9,11-dienoic acid

The predominant diene conjugated acyl residue in triacylglycerols, cholesteryl esters and phospholipids in human serum was identified by high performance liquid chromatography and capillary gas chromatography-mass spectrometry. It is an octadeca -9,11-dienoic acid.

Biochemical and histological assessment of hepatic lipid in sudden infant death syndrome

A biochemical and histological study of hepatic lipid in children dying from the sudden infant death syndrome (SIDS) and children of a similar age dying explicably are reported. Contrary to a previous report based on histological assessment of hepatic lipid, no significant increase of total lipid content in livers of children dying from SIDS was found. Analysis of hepatic phospholipid fatty acid esters, however, revealed a significant difference between SIDS and children of similar age dying acutely and explicably. The phospholipid abnormality found in SIDS was similar to that found in children dying subacutely with hypoxia and would be consistent with increased cell membrane fluidity. The implications of these findings in the pathogenesis of SIDS are discussed.

General methods for the analysis of metabolic profiles of bile acids and related compounds in feces

A general method is described for the detailed qualitative and quantitative analysis of bile acids and related compounds from feces. The technique utilizes a novel combination of liquid-gel and liquid-solid extraction, lipophilic ion exchange chromatography, and capillary column gas-liquid chromatography coupled to mass spectrometry, which permits the detailed composition of bile acids in feces in terms of both the individual bile acids present and their mode of conjugation in the original fecal sample. The extraction, purification, and isolation procedures have been evaluated using fecal samples containing endogenous radioactive bile acid metabolites and from the addition of radiolabeled standards to fecal homogenates. The applicability of the general procedure is illustrated with examples from the analysis of bile acids and sterols in the feces collected from normal healthy subjects, patients with chronic diarrhea, and an adult female Sprague-Dawley rat. The flexibility of the method, and the general problems encountered in the extraction, purification, and isolation of bile acids and related classes of compounds from feces for subsequent analysis of gas-liquid chromatography are discussed in detail.

Measurement of enterolactone and enterodiol, the first mammalian lignans, using stable isotope dilution and gas chromatography mass spectrometry

Methods are described to extract and measure 2,3-bis(3-hydroxybenzyl)-gamma-butyrolactone (enterolactone) and 2,3-bis(3-hydroxybenzyl)butane-1,4-diol (enterodiol) from physiological fluids. They are based on the use of stable labelled analogues of each compound as internal standards with end point assay being by gas chromatography mass spectrometry. The methods were developed to quantify enterolactone and enterodiol in experiments designed to investigate the significance and source of these compounds in man and animals. Examples of studies on human ovarian blood and investigations of their excretion in urine following dietary manipulation are described.

The bile acid composition of gastric contents from neonates with high intestinal obstruction

The study was designed to identify 'atypical' bile acids in gastric contents from three neonates with high intestinal obstruction on the basis that this was likely to represent a rich source of primary bile acids. Cholic acid was the major component, and related 'atypical' bile acids included its C-3 and C-7 oxidation products, its 3 beta-epimer and 2 beta- and 6 alpha-hydroxylation products. Allocholic acid was the only 5 alpha-cholanic acid derivative identified. 7 alpha, 12 alpha-Dihydroxy-3-oxochol-4-en-24-oic acid was found in all three specimens and might be an intermediate in a biosynthetic pathway from cholesterol to cholic acid in which side-chain oxidation precedes at least some of the nuclear changes. Side-chain-hydroxylated derivatives of trihydroxycoprostanic acid were also detected and these may represent intermediates in biosynthetic pathways from cholesterol to cholic acid via 5 beta-cholestan-3 alpha, 7 alpha, 12 alpha-triol. The most abundant bile acid of this type was (25 epsilon)-3 alpha, 7 alpha, 12 alpha, 25-tetrahydroxy-5 beta-cholestan-26-oic acid, which suggested that C-25 hydroxylation may be an important step in the shortening of the C8 side chain of the cholestane triol to the C5 side chain of cholic acid in the neonatal period. Bile acids lacking a substituent at C-12 included chenodeoxycholic acid, its C-3 and C-7 oxidation products, its 3 beta-epimer and its 6 alpha-hydroxylation product (hyocholic acid).

Diurnal changes in serum unconjugated bile acids in normal man

Unconjugated bile acids were measured using gas chromatography-mass spectrometry in the serum of two subjects throughout a 24 hour period and in two other subjects over a six hour period after breakfast. Unconjugated bile acids were found in all samples of serum and included cholic, chenodeoxycholic, deoxycholic, 3 beta, 7 alpha-dihydroxy-5 beta-cholanic (iso-chenodeoxycholic), ursodeoxycholic, 3 beta, 7 beta-dihydroxy-5 beta-cholanic (iso-ursodeoxycholic), 3 beta-hydroxy-5-cholenoic, and lithocholic acids. The maximum concentration of each bile acid generally occurred between breakfast and dinner and total unconjugated bile acid concentrations attained levels of between 2-3 mumol/l. Concentrations increased after breakfast and were often as high as 30-40% of the conjugated bile acid glycocholate, but returned to fasting levels in the absence of lunch. The intestinal absorption of unconjugated bile acids is therefore of greater quantitative importance than was previously thought.

Bile acid profiles of human serum and skin interstitial fluid and their relationship to pruritus studied by gas chromatography-mass spectrometry

1. Pruritus was assessed in 19 patients by measurement of nocturnal limb movement. 2. Serum (nine pruritic, ten non-pruritic) and interstitial fluid (five pruritic, three non-pruritic) bile acids were fractionated according to their mode of conjugation by using DEAP-Sephadex LH-20 and measured by gas chromatography-mass spectrometry. 3. No correlation was found between serum or interstitial fluid total bile acid or individual bile acid concentrations and pruritus. Bile acid profiles in the two groups of patients were similar and there was no correlation between pruritus and the conjugation pattern. 4. Te bile acid profile of interstitial fluid reflected that of serum and a linear relationship was found between serum and interstitial fluid bile acid concentrations (r ;.95, P less than 0.001). 5. The proportion of bile acid sulphate in interstitial fluid was significantly smaller than that in serum (P less than 0.025), where sulphates accounted for up to 46% of the total bile acids. 6. In three patients, a decrease in serum bile acid concentrations achieved by percutaneous transhepatic biliary drainage had little or no effect on pruritus. 7. These findings suggest that bile acids do not have a causative role in the pruritus of cholestatic liver disease.

The identification of the weak oestrogen equol [7-hydroxy-3-(4'-hydroxyphenyl)chroman] in human urine

The identification (by gas chromatography-mass spectrometry and n.m.r.) for the first time of the weak oestrogen equol [7-hydroxy-3-(4'-hydroxyphenyl)chroman] in human urine is described. Preliminary results of its quantitative excretion in urine are reported and the potential significance of the occurrence of this compound is discussed.