SOLUTION CONFORMATIONS OF THE PITUITARY OPIOID PEPTIDE DYNORPHIN-(1-13)

Circular dichroism [CD] spectra were measured for dynorphin-(1-13) in water and in solutions of sodium dodecyl sulfate [SDS] and L-.alpha.-lysophosphatidylcholine (palmitoyl). Spectra in H2O had the features expected for a peptide containing little, if any, order. Small changes are brought about by L-.alpha.-lysophosphatidylcholine (palmitoyl), but the resulting spectrum retained the characteristics expected for a random coil. SDS produced significant changes expected for induction of .alpha. helical content. Quantitative analysis of the CD spectra suggests the conformation changes from .apprx. 5% helix in H2O to 17% helix in SDS. Formulation of the configuration partition function predicts a change in helical content from 1 to 19%. The ordering influence is felt most strongly by those residues immediately following the enkephalin sequence.