Abstract
The partition of 3, 3'-dipropyl-2, 2'-thiadicarbocyanine, diS-C3 (5), between the i terior of bovine red cells and bulk aqucous medium was measured by using fluorescence spectroscopy. Inside the cells (concentrated hemoglobin phase), diS-C3 (5) is intensely concentrated and consequently forms the nonfluorescent dimer. Valinomycin stimulates K+ transport across the cell membrane and the resulting change in membrane potential induces an alteration of the partitioning and the dimerization of diS-C3 (5). The changes in membrane potential and permeability of the red cell membrane to K+ were quantitatively associated with this dimerizatioo. The permeability of the membrane to K+ estimated here can be correlated with the characteristic properties of bovine red cell membrane, that is, the high content of sphingomyelin and the rigidity of this membrane.
