Phenylalanine interaction with lipid monolayers at different pHs

• Phe inserts in DPPC monolayers at pH 5.0.
• Phe forms a complex with PC molecules.
• Phe form film on the monolayer surface at pH 7.3.

The influence of Phe on the surface pressure of 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) monolayers at the air–water interface was studied at different initial surface pressures (26 and 40 mN/m) and two pHs (5.0 and 7.3) at constant temperature (20 °C). Changes produced by the aminoacid added to the subphase on the surface pressure and on the dipole potential of lipid monolayers were measured at a fixed area. Compressibility properties of the monolayers at different pHs were studied by (π–A) isotherms. The results suggest that Phe intercalates into a DPPC film at the air–water interface at pH 5 and forms a different arrangement at pH 7.3.The possible relevance of these results of the effect of Phe in physiological conditions is discussed.

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