The structure of the core part of Proteus mirabilis O27 lipopolysaccharidewith a new type of glycosidic linkage

The structural assignment of the intact lipopolysaccharide core from Proteu s mirabilis O27 has been completed based on a combination of chemical degra dation studies, NMR spectroscopy and ES-MS spectroscopy. The overall core s tructure is as follows: [GRAPHICS] where all sugars are in the pyranose form except the N-acetylglycosamine re sidue, Hep refers to L-glycero-alpha-D-manno-heptopyranose and alpha-DDHep to D-glyeero-alpha-D-manno-heptopyranose. Bold italics indicate non-stoichi ometric substituents. A new type of glycosidic linkage has been discovered wherein a GalNAc residue is linked as an open form acetal to the 4- and 6-p ositions of a 2-amino-2-deoxygalactopyranose residue. This structural eleme nt is abbreviated GaloNAc-4,6-, where the 'o' indicates the open form of th e sugar residue. (C) 1999 Elsevier Science Ltd. All rights reserved.