Residual dipolar coupling requires the use of a liquid crystalline medium, for example, filamentous phage particles in water, to induce partial alignment of molecules within the magnetic field of an NMR. This partial alignment allows anisotropic dipolar coupling of magnetically active nuclei to be measured.  The magnitude of the coupling can be used to determine the vector between the coupled nuclei with respect to the molecular alignment vector.  A set of vector data for multiple atoms, including single- and multiple-bond couplings of hydrogen and carbon atoms, within a molecule can allow for the determination of stereochemistry and conformation.

            Our lab has developed cyclic bis-amino acid building blocks that are used to form oligomeric structures of designed shape. These monomers are linked by two amide bonds in the form of diketopiperazine rings to form spiro-ladder oligomers. 

The two molecules I studied were formed from three stereoisomers of one class of building block derived from 4-hydroxy-proline (Pro4).   These spiro-ladder oligomeric structures consisted of seven and nine Pro4 residues, varying in the sequence and number of monomers used, and were predicted by modeling to form “C” and “S” shaped turns respectively.  The stereochemistry of the constituent residues was known prior to formation of the sequence by solid phase peptide synthesis, and the first goal of the study was confirmation of their stereochemistry after oligomer synthesis. Secondly, the study of the conformations of the ring systems was used to attempt to establish the aqueous solution phase structure of the molecules as aligned by fd phage.  The data acquired from this study is to be used to fine tune software used for the design of future structures.