solution structure of a peptide nucleic acid duplex from nmr data features and limitations this paper describes the results of a 1d and 2d nmr spectroscopy study of a palindromic 8base pair pna duplex ggcatgcc in h2o and h2od2o solutions the 1h nmr peaks have been assigned for most of the protons of the six central base pairs as well as for several amide protons of the backbone the resulting 36 interbase and basebackbone distance restraints were used together with watsoncrick restraints to generate the pna duplex structure in the course of 10 independent simulated annealing runs followed by restrained molecular dynamics md simulations in explicit water the resulting pna structures correspond to a ptype helix with helical parameters close to those observed in the crystal structures of pna based on the current limited number of restraints obtained from nmr spectra alternative structures obtained by md from starting pna models based on dna cannot be ruled out and are also discussed