A polyion-complexed lipid membrane was prepared from dioctadecyldimethylammonium bromide (2C(18)N2C(1)) and sodium dextran sulfate. Controlled-pore glass (CPG) was coated with the obtained lipid membrane and applied to the adsorption of fluorescein-lipopolysaccharide (FITC-LPS) and bovine serum albumin (BSA). At temperatures not higher than the Lipid phase transition (T-c = 43 degrees C, DSC), FITC-LPS was selectively adsorbed to CPG coated with the lipid membrane from BSA/FITC-LPS mixed solution (pH 6.8). On the other hand, at the phase transition temperature or higher both FITC-LPS and BSA were adsorbed. When polyion-complexed lipid membrane of didodecyldimethylammonium bromide (2C(12)N2C(1)) or octadecyltrimethylammonium bromide (C(18)N3C(1)) was used, phase transition was not observed and both FITC-LPS and BSA were adsorbed. FITC-LPS is probably adsorbed by inserting its fatty acid alkyl chains into the lipid membrane on CPG. Because of the structural similarity, FITC-LPS could interact with not only the lipid membrane in fluid liquid crystalline phase but that in rigid gel phase. On the other hand, the lipid membrane probably has to be in relatively fluid state to interact with the hydrophobic region of BSA. Therefore the selective adsorption of FITC-LPS from BSA/FITC-LPS solution was achieved by only 2C(18)N2C(1) polyion-complexed membrane in the rigid gel phase.