The interaction of protein monolayers with dissolved proteins - I. Fibrinogen, thrombin and plasma albumin

Abstract

The proteins concerned have been spread at the air/water interface on a substrate at physio­logical ionic strengths. Spread proteinAhas been ‘injected’ with dissolved proteinB, and the increase in pressure observed has been attributed to adsorption. This adsorption has been found to depend on the area per molecule of the spread protein, reaching a maximum value at an intermediate area value. It is postulated that adsorption occurs by hydrogen bonds betweenBandA, and that at a certain stage of compression the bonding groups inAturn so as to form hydrogen bondswithinthe monolayer, a theory which accords with compressibility and viscosity data on the monolayers. The rate of increase of pressure depends markedly on ionic strength suggesting that the rate of adsorption is influenced by the interaction of ionic groups inAandB. No evidence was obtained for a surface clotting reaction or specific interaction between fibrinogen and thrombin, whichever protein formed the monolayer, suggesting that the specific interaction involves at least two groups in each protein held at a critical spacing.