SURFACE-FILMS OF AN OVOMUCOID AT AN AIR-WATER-INTERFACE

Studies are made of isotherms PI(A) (where PI is two-dimensional pressure and A is the area per 1 mg of substance) of monolayers (ML) of an ovomucoid (OM). The form of the isotherm depends on the amount of deposited protein c(s) and spreading time tsp. At c(s) > 1.7.10(-9) moles, an inflection is seen on the isotherm with compression. The appearance of this inflection is connected with collapse of the structured monolayer. At c(s) < 1.7.10(-9) moles, the moles of the monolayer are unassociated molecules of an ovomucoid, while quarternary structures of a cylindrical OM with a degree of association n = 3 and axial ratio 1:5 appear at c(s) > 1.7-10(-9) moles. The existence of the contricted section up to the points of inflection is due to the occurrence of liquid-crystalline order and the appearance of a mononolecular nematic layer. The estimated elastic modulus of the monolayer in compression approximately 20-25 mN/cm2 and the persistent particle length approximately 100 angstrom. Relaxation of PI was studied at PI > PI(c) for ovomucoid film with a compressed layer of constant area due to the nucleation of a bulk phase. Subsequent expansion of the monolayer was accompanied by the appearance of a hysteresis loop, which is connected with the spreading of bulk segments of the nematic into the monolayer.