Calorimetric, nuclear magnetic resonance and fluorescence spectroscopic techniques are used to characterize the erythrocyte membrane structures involved in anion transport and also the interactions of these structures with other major components of the erythrocyte membrane. Special attention is devoted to understanding the mechanisms of noncompetitive inhibition of anion transport by membrane perturbants such as anesthetics, calcium, and low or high pH. Other experiments have been designed to determine the distances between major membrane components using fluorescence energy transfer as a "membrane yardstick".