The goal of this project is to find the specific interaction of the agonist DPDPE in the human delta opioid receptor. This will be accomlished through that incoporation of a photoaffinity labled amino acid, 4-azidotrafluorphylalanine, into DPDPE. After formation of the DPDPE analopgues, they will be allowed to interact with the opioid receptor nd bindinf affinities will be obtained. The photoaffinity labled DPDPE will covalently link to the receptor using a pulsed laer or a 200W arc-lamp. The bound DPDPE/receptor will then solubized and purified using affinity chromatography. This will then be using trysin and chymothrypsin and the fragments will be analyzed via mass spectroscopy to determine where the DPDPE bound to the recetor. Once this is accomplished, site specific mutagenisis will be done on the human delta opioid receptor in order to determine how binding affinities are affected.