600 MHz NMR studies of human articular cartilage keratan sulfates

The use of high-field two-dimensional H-1-correlation data is described for the detailed comparison of intact keratan sulfate polymer chains derived f rom human articular cartilage sources as a function of age. For fetal mater ial the nonreducing chain termini are shown to be sparsely capped by sialyl groups which, if present, are exclusively (alpha 2-3)-linked to an unsulfa ted galactose residue. The asialo capping segment has the structure: Gal-Gl cNAc6S-Gal-GlcNAc6S-. Examination of keratan sulfate from 10-year-old carti lage shows that capping by sialyl groups is complete, with (alpha 2-3)-link ages predominant; for both this and the 38-year-old cartilage the three cap ping structures: NeuAc(alpha 2-3)-Gal-GlcNAc6S-Gal-GlcNAc6S-, NeuAc(alpha 2 -3)-Gal-GlcNAc6S-Gal6S-GlcNAc6S- and NeuAc(alpha 2-3)-Gal6S-GlcNAc6S-Gal6S- GlcNAc6S- are clearly recognizable. The level of (alpha 2-6)-linked chain c apping sialyl groups is significant for 38-year-old cartilage keratan sulfa te. Structural information concerning the linkage region to protein and the distribution of galactose environments is readily obtained from the spectr a, Signal complexities severely limit the usefulness of two-dimensional cor relation spectroscopy at 600 MHz for the examination of N-acetylglucosamine residues within the poly(N-acetyllactosamine) repeat sequence and signals representing fucose placements remain undifferentiated. This nondestructive approach complements current degradative methods for the structural examin ation of keratan sulfates.