The Equilibria of Phosphatidylethanolamine-Cholesterol and Phosphatidylcholine–Phosphatidylethanolamine in Monolayers at the Air/Water Interface

2012

J Membrane Biol

Monolayers of sphingomyelin (SM), ceramide (Cer) and cholesterol (Ch) and binary mixtures SM–Ch, SM–Cer and Cer–Ch were investigated at the air–water interface. SM, Cer and Ch were used in the experiment. The surface tension values of pure and mixed monolayers were used to calculate π-A isotherms. Surface tension measurements were carried out at 22 °C using a Teflon trough and a Nima 9000 tensiometer. Interactions between sphingolipid and Ch as well as sphingolipid and another sphingolipid 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 Gibbs free energy values of SM–Ch, SM–Cer and Cer–Ch complexes. We considered the equilibrium between the individual components and the complex and established that sphingolipid and Ch as well as sphingolipid and another sphingolipid formed highly stable 1:1 complexes.

Section: Introductionsupporting

confidence: 79%

“…The homemade, computer-controlled apparatus used for surface tension measurements was presented previously (Petelska and Figaszewski 2009). …”

Section: Methodsmentioning

confidence: 99%

Section: Theorymentioning

confidence: 99%

See 1 more Smart Citation

The Equilibria of Sphingolipid-Cholesterol and Sphingolipid–Sphingolipid in Monolayers at the Air–Water Interface

2012

J Membrane Biol

“…16 and 17 may be used for verification of slopes obtained either from theory or by experiment. Agreement between the slopes indicates that the method of calculating K AB and S AB is correct [20,21].…”

Section: Theorymentioning

confidence: 92%

“…The homemade computer-controlled apparatus used for surface tension measurements was presented in the previous article [20,21]. The surface tension measurements were carried out at the water/air interface at 22°C, and were expressed as surface pressure-area per molecule (p-A) isotherms.…”

Section: Measuring Apparatus and Measuring Proceduresmentioning

confidence: 99%

The Equilibrium of Phosphatidylcholine–Amino Acid System in Monolayer at the Air/water Interface

Naumowicz

2010

Cell Biochem Biophys

Self Cite

Monolayers of phosphatidylcholine, tyrosine, and phenylalanine and binary mixtures phosphatidylcholine-tyrosine or phosphatidylcholine-phenylalanine were investigated at the air/water interface. Phosphatidylcholine (lecithin, PC), tyrosine (Tyr), and phenylalanine (Phe) were used in the experiment. The surface tension values of pure and mixed monolayers were used to calculate π-A isotherms. The surface tension measurements were carried out at 22°C using an improved Teflon trough and a Nima 9000 tensiometer. The Teflon trough was filled with a subphase of triple-distilled water. Known amounts of lipid dissolved in 1-chloropropane were placed at the surface using a syringe. The interactions between lecithin and amino acid 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 of PC-Tyr as well as PC-Phe complexes. We considered the equilibrium between the individual components and the complex and established that lecithin and amino acid formed highly stable 1:1 complex.

pH Effect of the Sphingomyelin Membrane Interfacial Tension

2009

J Membrane Biol

The effect of pH on the interfacial tension of a sphingomyelin membrane in aqueous solution has been studied. Three models describing H(+) and OH(-) ion adsorption on the bilayer lipid surface are presented. In models I and II, the membrane surface is continuous, with uniformly distributed functional groups as centers of H(+) and OH(-) ion adsorption. In model III, the membrane surface is composed of lipid molecules, with and without adsorbed H(+) and OH(-) ions. The contribution of each individual lipid molecule to the overall interfacial tension of the bilayer was assumed to be additive in models I and II. In model III, the Gibbs isotherm was used to describe adsorption of H(+) and OH(-) ions at the bilayer surface. Theoretical equations are derived to describe the interfacial tension as a function of pH for all three models. Maximum interfacial tension was observed experimentally at the isoelectric point.