A simple apparatus for measurement of protein monofilm expansion at air-water interface in response to soluble reactants in the subsolution

A new apparatus and technique for the study of the reaction of macromolecules at the air-water interface with soluble substances in the subsolution is described. A system of piston oils and plastic float with mercury seals is employed to monitor the monofilm area changes at constant pressure. The reaction trays are milled from Teflon, which permits easy instrumentation and cleaning. The test monofilm is compressed to a predetermined pressure by a "piston oil" and is allowed to expand against the oil area on injection of a suitable reactant. The film expansion is isobaric owing to the unique characteristic of the piston oil. A plastic float with mercury seals divides the piston oil area from the test monofilm, and responds to small pressure changes in the latter by an appropriate displacement.