It is proposed to determine the structure of non-enzyme proteins and of peptide hormones as the basis for consideration of structure function relationships in systems where the enzyme substrate "induced fit" model may be inappropriate. In particular, the structures of the prohormone proinsulin and of the peptide hormone oxytocin will be determined. The relationship between the structure of the insulin molecule as established in the rhombohedral form and its stereo-chemistry in the orthorhombic form will be studied. Solution of the proinsulin structure will then be sought by rigid-body search procedures. The laboratory studies of protein-protein interactions and co-crystallization phenomena will be continued. The development of criteria for the prediction of conformation in protein structure will continue. Our long range goal in X-ray diffraction is the development of methods for the X-ray crystal structure analysis of proteins and peptides which do not depend on the preparation of crystalline heavy-atom derivatives.