A solid phase- and chemical crosslinking-based technology was developed for determining the depths at which various protein constituents reside in a supramolecule. The usefulness of this technology was verified by trials using a synthetic three-protein complex on glass coverslips. This technology was further applied to investigate the localization of seven major protein components in the postsynaptic density, a landmark supramolecule of the excitatory synapses in mammalian brains. The technology reported here will supplement the already powerful proteomic methodologies in studying the structure/function relationships of supramolecules.