Glycoconjugates of the GI tract are important for microbial interactions. The expression of histo-blood group glycosyltransferases governs both the expression of blood group determinants and in part the structure and size of the glycoconjugates. Using neutral glycolipids isolated from the small intestine of a rare blood group O Le(a−b−) ABH secretor-negative (nonsecretor) individual we were able to map the “default” pathway of the individual lacking ABO, Lewis, and secretor glycosyltransferases. Structures were deduced with combined analysis of mass spectrometry (MALDI-TOF and ESI-MS/MS), and ¹H NMR (500 and 600 MHz). All structures present at a level >5% were structurally resolved and included two extended structures: Galβ4(Fucα3)GlcNAcβ3(Galβ4[Fucα3]GlcNAcβ6)Galβ4GlcNAcβ3Galβ4Glcβ1Cer and Galβ3GlcNAcβ3(Galβ4[Fucα3]GlcNAcβ6)Galβ3GlcNAcβ3Galβ4Glcβ1Cer. The first, a novel component, is based on a type 2 chain and bears the Le^x glycotopes on both its branches. The second, a major component, is based on a type 1 chain, which bears a 3-linked type 1 precursor (Le^c) glycotope and a 6-linked Le^x glycotope on its branches. This latter structure is identical to that previously isolated from plasma and characterized by MS and GC-MS but not by NMR. Structural resolution of these structures was supported by reanalysis of the blood group H–active decaosylceramides previously isolated from rat small intestine. Other minor linear monofucosylated penta-, hepta-, and difucosylated octaosylceramides, some bearing blood group determinants, were also identified. The cumulative data were used to define a default biosynthesis pathway where it can be seen that carbohydrate chain extension, in the absence of blood group glycosyltransferases, is controlled and regulated by non–blood group fucosylation and branching with type 2 Galβ4GlcNAc branches.

Function-Spacer-Lipid (FSL) constructs allow the surface characteristics of living cells and virions to be modified without loss of...