Conformational analysis of heparin epoxide: molecular mechanics computations.

The conformation of models of the epoxy-derivative of the glycosaminoglycan heparin has been studied by molecular mechanics calculations using a MM2-like force field extended with parameters for the oxirane ring. Two dimers, two trimers and several higher homologs modeling heparin epoxide were investigated, assuming the preferred 5H0 ring form of 2,3-anhydro-alpha-L-guluronic acid residue. Two-dimensional (phi; psi) maps of dimers showed the location of the energetically preferred conformers.

Conformational analysis of heparin epoxide in aqueous solution. An NMR relaxation study.

1H and 13C NMR relaxation measurements at various magnetic fields have been used to characterize the nature of overall and internal motions in heparin epoxide in aqueous solution. A two-dimensional homonuclear NOESY experiment showed a considerable number of cross-relaxing protons in the molecule. The inter-proton distances calculated from NOE data were compared with those obtained by molecular mechanics calculations.