IMMUNOLOGICAL ACTIVITY OF IGG LANGMUIR FILMS ORIENTED BY PROTEIN-A SUBLAYER

The immunological reaction ability of IgG Langmuir-Blodgett monolayers organized by means of a protein A sublayer has been studied by the gravimetric technique. In order to discriminate the effects of molecular orientation and to preserve the native structure of IgG molecules using the protein sublayer, the kinetics of specific and non-specific binding at an immunoglobulin monolayer deposited onto different substrates, such as a silanized aluminium surface and a surface covered by ovalbumin and protein A sublayers, are compared. It is shown that the prevailing effect is molecular orientation. A sublayer of protein A appeared not only to increase the specific sensitivity of the IgG monolayer but to decrease the non-specific binding as well. For this structure the sensitivity of a monolayer of rabbit anti-mouse IgG towards mouse IgG is 10 pM. The sensitivities in the case of a bare metal surface and ovalbumin sublayer are 10 and 100 times less, respectively. Protein A and ovalbumin sublayers are obtained by the Langmuir-Schaeffer technique. The formation of monolayers on the water-air interface and the deposition onto the solid substrate are studied by means of compression isotherms, gravimetric and ellipsometric techniques. It is shown that the solubility of protein A depends on the surface pressure increasing sharply after a certain value of the pressure. It is also shown that protein A can be deposited onto the substrate in the form of dense two-dimensional monolayers.