title: The equilibria of lipid-k(+) ions in monolayer at the air/water interface.
abstract: The effect of K(+) ion interaction with monolayers of phosphatidylcholine (lecithin, PC) or cholesterol (Ch) was investigated at the air/water interface. We present surface tension measurements of lipid monolayers obtained using a Langmuir method as a function of K(+) ion concentration. Measurements were carried out at 22°C using a Teflon trough and a Nima 9000 tensiometer. Interactions between lecithin and K(+) ions or Ch and K(+) ions result in significant deviations from the additivity rule. An equilibrium theory to describe the behavior of monolayer components at the air/water interface was developed in order to obtain the stability constants and area occupied by one molecule of lipid-K(+) ion complex (LK(+)). The stability constants for lecithin-K(+) ion (PCK(+)) complex, [Formula: see text], and for cholesterol-K(+) ion (ChK(+)) complex, [Formula: see text], were calculated by inserting the experimental data. The value of area occupied by one PCK(+) complex is 60 Å(2 )molecule(-1), while the area occupied by one ChK(+) complex is 40.9 Å(2 )molecule(-1). The complex formation energy (Gibbs free energy) values for the PCK(+) and ChK(+) complexes are -14.18 ± 0.71 and -16.92 ± 0.85 kJ mol(-1), respectively.
authors: Institute of Chemistry, University in Bialystok, Poland. aneta@uwb.edu.pl
authors: Aneta D
authors: AD
authors: Petelska
authors: Zbigniew A
authors: ZA
authors: Figaszewski
mesh_terms: D000388:Air; D002627:Chemistry, Physical; D002784:Cholesterol / Q000737:chemistry / Q000378:metabolism*; D057927:Hydrophobic and Hydrophilic Interactions; D007700:Kinetics; D010713:Phosphatidylcholines / Q000737:chemistry / Q000378:metabolism*; D011188:Potassium / Q000737:chemistry / Q000378:metabolism*; D013500:Surface Tension; D013816:Thermodynamics; D014867:Water
chemical_list: D010713:Phosphatidylcholines; D014867:Water; D002784:Cholesterol; D011188:Potassium