In blood‐group H substance from pig stomach cell linings, carbohydrate structures are known to occur which are O‐glycosidically linked via GalNAc to Ser or Thr of the polypeptide backbone. They have in common the Gal(β1→3)GalNAc core unit, which bears one or more N‐acetyllactosamine branches. The latter are terminated either by Fuc in (α1→2) linkage or by GlcNAc in (α1→44) linkage to Gal. Both terminal sequences are considered to be porcine blood‐group H antigenic determinants. Employing 500‐MHz 1H‐NMR spectroscopy, the spectral features of the oligosaccharide‐alditols corresponding to these chains were established. Insight could be gained into the microheterogeneity displayed by some of the alditol fractions as to the distribution of the terminating Fuc and GlcNAc residues over the various branches. Such information can hardly be obtained using other approaches.

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Six individual reduced pentasaccharides and hexasaccharides were isolated after sodium borohydride degradation of blood group substance H from pig stomach linings. Their structure was determined by means of periodate oxidation, methylation analysis, mass spectrometry, partial acid and enzymic hydrolysis and chromic anhydride oxidation. It has been found that all the oligosaccharides investigated contain the common tetrasaccharide core to which terminal a-L-fucose and N-acetyla-D-glucosamine residues are attached. Some problems of carbohydrate chain heterogeneity in blood group substances are discussed.A high degree of heterogeneity of blood group substances has been demonstrated quite recently [l, 21. However, the general principles of heterogeneity of the carbohydrate part of glycoproteins have not been clarified as yet and this problem seems to be important and attractive.In order to understand the general principle of heterogeneity of blood group substance carbohydrate chains we have to elucidate the structure of the reduced oligosaccharides arising after degradation of the biopolymer with alkaline sodium borohydride [ 2 ] . The separation of the total oligosaccharide fraction on Biogels has shown that the oligosaccharides formed consist of 2-3 to 15 -20 monosaccharide units, but one of the main oligosaccharide fractions consists of pentasaccharides and hexasaccharides. In the previous communication we reported on the structure of two reduced trisaccharides a-~-Fuc-(l -2 ) 8 -

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