Complete 1H and 13C spectrum of a polysaccharide isolated from Escherichia coli, which is the major component of the enterobacterial common antigen, has been analyzed through two-dimensional nuclear magnetic resonance spectroscopy. In addition, distance constraints from NOESY and ROESY experiments have been combined with molecular dynamic simulations to determine its major conformation in water solution. Data resulting from both free dynamic simulations and restrained dynamic simulations have been compared with experimental data and discussed.