Conformations of blood group H‐active oligosacharides of ovarian cyst mucins

Abstract

SynopsisSpectroscopic data and conformational energy calculations are reported for eight oligosaccharides from ovarian cyst mucins and from human milk, the nonreducing terminals of which have fucose (a1 -2)galactose linked either (Pl-3) (type I) or (pl-4)(type 11) to Nacetylglucosamine or in ( D l -3 ) linkage to galactosaminitol. The fully assigned proton nmr spectra are reported along with nuclear Overhauser enhancement (NOE) data. Amide proton coupling constants and vacuum-uv CD spectra provide information on the amide plane orientation and amide environment. Our results imply that the fucosidic dihedral angles are similar for all three cases and that the substantial differences in the chemical shifts of the fucosyl protons of type I, type 11, and 3-01 chains result from different perturbations by the amide group of the residue to which the P-galactose is linked. Stereopair diagrams of conformational models for both type I and I1 H chains are presented that are consistent with NOE, coupling constants, conformational energy calculations, and the CD data. While the temperature dependence of the observed NOE of penta-and hexasaccharides indicates that their rotational correlation times are strongly temperature dependent, we conclude that the conformations are essentially independent of temperature.

Neutral oligosaccharides of bovine submaxillary mucin

“…LSIMS of the permethylation product MH' m/z 1176 and the partially methylated alditol acetates (Table 2) were consistent with this interpretation, the latter clearly showing the GalNAc(1 -) and (-2,3)Gal(l -) features. (Table 8) matched previously recorded data [23,24,26] for a hexasaccharide having a terminal bloodgroup-H determinant on both arms. Its permethylated LSIMS MH' ion at m/z 1309 and intense fragment ions m/z 638/606, together with methylation analysis (Table 2), were in accord with this assignment.…”

“…The trisaccharide core structure GlcNAc(/YI -6)[Gal(/31-3)]GalNAcol (fractions N2-5/N3-4) and its analogue fucosylated at C2 of galactose on the (2-3 branch (fractions N2-6jN3-5) were identified by Tsuji and Osawa [lo] and have been characterised previously from other sources by 'H-NMR [18,20,[22][23][24][25]. Their structures were fully established in the present study (Tables 1, 2 and 8).…”

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

“…However, this may not be true for branches linked to GalNAcr-SerlThr rather than GalNAcol. The proposed spatial orientation of the periphcral substitutions, GlcNAcml-4 linked to Galpl-4GlcNAcfil-6 in fractions K2(3), K4(2), and K6(3) and Fucal-2 linked to Galpl3GalNAcol in fraction K6(3), suggest that these form relatively globular conformational domains as has been shown for the blood group and related antigens, H, A, B, Lea, Leh, SSEA-1 and their sialylated analogues [lX, 19,22,[28][29][30][31]. This, together with the possible restricted distribution of thc C?lcNAcnl-4Gal sequence and its relative abundance in human foetal gastrointestinal mucins, suggests its potential as an epithelial marker for differentiation stage and neoplastic transformation.…”

“…As discussed above for oligosaccharide K2(3), the H4 rcsonance of GalNAcol is particularly susceptible to changes in shielding depending on the substituent on Gal linked pl-3 to it. This, together with the identification of chemical shifts characteristic of a GlcNAcal4GlcNAcfll-6 branch (discussed above) and those for fucose linked a1-2 to Gal in p1-3 linkage to GalNAcol [14,[22][23][24] gave the assignment shown in Tablcs 2 and 7 for the major component of fraction K6(3).…”

Separation of positional isomers of oligosaccharides and glycopeptides by high-performance anion-exchange chromatography with pulsed amperometric detection.

“…1 and Table 1 show that lactose-N-tetraose and lactose-N-neotetraose are separated by 8.4 min. Assuming a greater acidity for the 3-OH of GlcNAc relative to the 4-OH, we expected that compound 4 would be a more acidic oligosaccharide and, therefore, elute after compound 5. Conformational analysis of these two types of linkages showed that the disaccharide unit, Gal(,81-3)GlcNAc, has a distinct hydrophilic face produced by both monosaccharides (33,34). In contrast for Gal(1-4)GlcNAc, the hydroxyl groups of galactose and GlcNAc are in distinct planes and do not form a "sheet" of hydrophilic residues.…”