ABSTRACT
This chapter provides a brief account on the part of proximity measurements. It tries to avoid methodological discussions and focused our interest on liposomes, specialized receptor systems of sensory organs, major receptor elements of the muscle and nerve receptor families, and cytoskeletal and blood clotting factors. The chapter discusses that the fluorescence energy transfer (FRET) technique is a powerful method for studying interactions of molecules in membranes. Relative energy transfer efficiency values between suitably labeled antigens provide a powerful tool even for a two-dimensional mapping of cell surface elements, based on their stepwise FRET measurements on the same cell types, under identical conditions. The primary and unique property of the vertebrate immune system lies in its ability to distinguish between closely related, but different molecular structures. Binding of the factor to its cell surface receptor triggers the immediate stimulation of a receptor-associated tyrosine kinase activity and results in a variety of early and late cellular responses.
