Monolayer properties of synthesized tyrosyl esters

Lipase-catalyzed synthesis of eight fatty acid tyrosyl esters (TyC2 to TyC18:1) was investigated using non commercial lipases from Rhizopus oryzae and Staphylococcus xylosus immobilized onto CaCO3. The monomolecular film technique was used to compare the ability of the various synthesized tyrosyl fatty acid esters to form a stable monolayer at the air/water interface and their capacity to interact with a phospholipid monolayer. The measurements of surface pressure versus the molecular area shows that, in contrast to tyrosol esterified with short and medium chains (acetic (TyC2), propionic (TyC3), caprylic (TyC8) and capric (TyC10) acids), tyrosol esterified with long chains: lauric (TyC12), palmitic (TyC16), stearic (TyC18) and oleic (TyC18:1) acids are able to form a stable monolayer at the air/water interface. A direct correlation was observed between the length of the saturated acyl chain of the derivatives and their corresponding collapse pressures. The presence of unsaturation reduces the collapse pressure value. The interaction of tyrosyl esters with a phospholipid monolayer was studied and the critical surface pressure (πc) of each ester was determined. Only medium and long chain (TyC8 to TyC18:1) derivatives esters were found to interact efficiently with DiC12PC film.