Structure elucidation of blood group B-like and I-active ceramide eicosa- and pentacosasaccharides from rabbit erythrocyte membranes by combined gas chromatography-mass spectrometry; electron-impact and fast-atom-bombardment mass spectrometry; and two-dimensional correlated, relayed-coherence transfer, and nuclear Overhauser effect 500-MHz 1H-n.m.r. spectroscopy.

The structures of two glycosphingolipids, a ceramide eicosasaccharide BIrab-3 and a ceramide pentacosasaccharide BIrab-4 with "B-like" and distinct I blood-group activity, isolated in high yield from rabbit erythrocyte membranes, were investigated. The determination of their general structure, alpha-D-Galp-(1----3)-beta-D-Galp-(1----4)-beta-D-GlcpNAc-(1----3)- [alpha-D-Galp-(1----3)-beta-D-Galp-(1----4)-beta-D-Glcp-NAc-(1----6)]-be ta- D-Galp-(1----n4)-beta-D-GlcpNAc-(1----3)-beta-D-Galp-(1----4)-beta-D-Gl cp- (1----1)-ceramide, with n = 3 for BIrab-3 and n = 4 for BIrab-4, was based on the results of methylation analysis, fast-atom-bombardment and electron-impact mass spectrometry, 1D and 2D COSY, RCT, and n.O.e. 1H-N.m.r. spectra, and specific enzymic and chemical degradation.