Effect of chloroquine and O,O'-bis(diethylaminoethyl)hexestrol on acidic phospholipid membranes

The amphiphilic drugs chloroquine and O,O'-bis(diethylaminoethyl)hexestrol are able to form complexes with the acidic-phospholipid 1,2-dipalmitoyl-sn-glycero-3-phosphoglycerol. The dissociation constants of the complexes with chloroquine are independent of pH in the range investigated here (4--7) as well as of temperature (4 degrees C--40 degrees C). The phase transition temperature of phospholipid is markedly reduced by both drugs, the effect is reversible by addition of Ca2.