title: The equilibrium of phosphatidylcholine-amino acid system in monolayer at the air/water interface.
abstract: 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.
authors.affiliation: Institute of Chemistry, University of Bialystok, Al. J. Pilsudskiego 11/4, 15-443 Bialystok, Poland. elchem@uwb.edu.pl
authors.forename: Aneta D
authors.initials: AD
authors.lastname: Petelska
authors.forename: Monika
authors.initials: M
authors.lastname: Naumowicz
authors.forename: Zbigniew A
authors.initials: ZA
authors.lastname: Figaszewski
mesh_terms: D000388:Air; D000596:Amino Acids / Q000737:chemistry*; D010649:Phenylalanine / Q000737:chemistry; D010713:Phosphatidylcholines / Q000737:chemistry*; D013500:Surface Tension; D014443:Tyrosine / Q000737:chemistry; D014867:Water / Q000737:chemistry*
chemical_list: D000596:Amino Acids; D010713:Phosphatidylcholines; D014867:Water; D014443:Tyrosine; D010649:Phenylalanine