Structural analysis of the lipopolysaccharide (LPS) from nontypeableHaemophilus influenzaestrain 981 has been achieved using NMRspectroscopy and ESI-MS on O-deacylatedLPSand core oligosaccharide (OS)material as well as by ESI-MS n on permethylated dephosphorylated OS. A heterogeneous glycoform population was identified, resulting from the variable length of the OS branches attached to the glucose residue in the common structural element of H. influenzae LPS, L-a-D-Hepp-(1fi2)-[PEtnfi6]-L-a-D-Hepp-(1fi3)-[b-D-Glcp-(1fi4)]-L-a-D-Hepp-(1fi5)-[PPEtnfi4]-a-Kdop-(2fi6)-Lipid A
