Recent advances in the field of peptide chemistry and gene technology have resulted in an explosive accumulation of information on biologically active pep tides and functional proteins. Because of the importance of such peptides and proteins in the role of cellular or extracellular regulatory mechanisms and their potential therapeutic value, an understanding of their detailed interactions with the specific receptor should provide useful information for structure-activity studies. These problems have been approached in many ways. However, despite our efforts, many gaps in our knowledge of...