Investigation of the Interactions of Two Potential Sensing Cyanine Dyes: 3,3'-Dipropylthiadicarbocyanine Iodide and 3,3'-Dipropyloxadicarbocyanine Iodide with Erythrocytes. Ghosts and Phospholipid Vesicles

摘要

The main goals of the experiments were: (1) to identify the similarities and differences in the manner in which two potential sensing cyanine dyes, 3,3'-dipropyloxadicarbocyanine iodide (di-O-C sub 3 (5)) and 3,3'-dipropylthiadicarbocyanine iodide (di-S-C sub 3 (5)), interact with erythrocytes, ghosts, and phospholipid vesicles and (2) to construct a theoretical model, based on potential energy considerations, which accurately describes the binding of di-O-C sub 3 (5) to intact rat erythrocytes. The experimental methods employed relied on two types of spectroscopic information. Dye absorption spectra were evaluated in the presence of normally polarized and hyperpolarized membrane preparations (whole cells, ghosts, and vesicles), while dye binding to the various preparations was evaluated using fluorometric assay techniques. The theoretical model proposed implicates concentrated dye binding at the membrane interfaces. Computer searches for the appropriate binding parameters result in theoretical calculations which agree closely with experimental findings. The predicted well depth at the membrane interfaces approximates estimates of the potential energy barrier to the transport of lipophilic ions across bilayers. The predicted transmembrane potential fraction overestimates measurements of the membrane potential. The model needs modification to satisfactorily explain all facets of membrane binding. (ERA citation 04:014577)