Dependence of Peptide Self-Association on Intermolecular Interaction by PFGNMR in TFE Aqueous Solution: C-terminal Analogues of NPY as Model Peptides

We have investigated the dependence of peptide oligomerization on intermolecular interaction in terms of both energetic and structural effect by PFGNMR. Three peptides, NPY[20-36], Pro34-NPY[20-36] and NPY[21-31], which are related to human NPY, were synthesized as models in this work. In contrast to NPY[20-36], both Pro34-NPY[20-36] and NPY[21-31] were found with descendent affinity with TFE cluster and continuous dissociating with increased temperature. The observed results can be accounted by the entropic change with temperature and the varied hydrophobic interactions between species due to the differed structures of peptides from each other. The removal of helical secondary structure or residues from C-terminal region may increase the energetic difference between peptide-peptide self-associating and peptidesolvent binding. This increased energetic difference leads to larger dependence of association-dissociation equilibrium on temperature and entropic increase while dissociating.