The activation of surface films of lecithin by amphipathic molecules

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Abstract
P32-lecithin of high specific activity has been prepared biosynthetically with baker''s yeast. The p32-iecithln has been used as a surface film to study the action of a Penicillium notatum phospholipase preparation. Loss of counts from the surface film into the bulk aqueous phase was used as a measure of enzymic activity. The enzyme preparation was without action on a film of lecithin but readily lowered the counting rate from a surface film of lecithin plus dicetylphosphoric acid. The loss of counts from the surface film did not occur on altering the pH of the aqueous phase from 3.3 to 4.4, which is known to inhibit the enzyme system. It is concluded that the presence of a net surplus of negative groups is a direct requirement for the initiation of the enzymic attack on a lecithin surface.