INFLUENCE OF COMPETITIVE ADSORPTION OF A LYSOPALMITOYLPHOSPHATIDYLCHOLINE ON THE FUNCTIONAL-PROPERTIES OF PUROINDOLINE, A LIPID-BINDING PROTEIN ISOLATED FROM WHEAT-FLOUR

The functional properties of a low molecular weight lipid-binding prot ein, puroindoline from wheat, were studied as a function of lysophosph atidylcholine (LPC) concentration. Puroindoline bound approximately fi ve LPC molecules in a positively cooperative manner with a dissociatio n constant of 54.3 muM. The foaming properties of puroindoline were en hanced in mixtures containing LPC, and maximum stability was observed in the range of LPC to puroindoline molar ratios (R) of 1-10. The prop erties of isolated foam lamellae (thin films) were investigated to exp lain this observation. Film drainage, equilibrium thickness, surface d iffusion in the adsorbed layer by fluorescence recovery after photoble aching, and surface displacement measurements were made. We conclude t hat the foaming properties of this highly foam active protein are enha nced by addition of LPC, probably by formation of a complex, which red uces puroindoline aggregation at the interface. However, foam stabilit y begins to decrease once there is enough LPC present in the system to allow the protein to diffuse laterally in the adsorbed layer.