Structural and functional properties of amphiphilic polyelectrolyte based Langmuir films from antibodies

Amplication of amphiphilic polyelectrolytes (APEs) made it possible monomol ecular films of antibodies, enzymes, and other proteins with high surface c oncentration of these molecules to be obtained, as well as catalytic parame ters of biochemical reactions to be changed significantly due to formation of condensed dimeric protein layers. In this work, we optimized the procedure of preparation of APE-based Langmu ir films of antibodies. We investigated Langmuir films composed of monoclon al antibodies (Ab) against the hepatitus B virus surface antigen (HBsAg) an d the following APEs: 1) copolymer of metacrylic acid with lauryl metacryla t at a molar ratio of 1 : 9 and polymerization degree of 100-300 (MAA-LMA); 2) linear polyethylenimine with 70% of monomer units being modified by lau rylbromid (PEI-L70); 3) branched polyethylenimine with 12% of monomer units being modified by cetylbromid, and 88% - by ethylbromid (PEI-B12). The phy sicochemical and immunochemical properties (based on enzyme immunoassay) of the Langmuir films obtained were studied and compared with those of Langmu ir film of Ab without APE and of Ab adsorbed on polystyrene and graphite. T he films with APE were found to be functionally more active than those with out APE, and the films with PEI - more :active than the film with MAA-LMA. The physicochemical parameters of Langmuir films depend on the polymer used . Atomic force microscopy (AFM) was used to investigate the structural prop erties of the Ab films obtained. We observed Langmuir films of Ab and MAA-L MA as dense films consisting of two components: a granular film resembling the Langmuir Ab film and separate beads that increase their volume and decr ease in number with the increase in the surface pressure during the Langmui r film formation. We suggest these beads to be pure polymer. The Langmuir A b films with PEI have ruptures. The structure of these films altered with c hanges in the surface pressure, but a relative area of the Ab-PEI films rem ained virtually constant.