Wechselwirkung pflanzlicher Wachstumshormone mit Membranen

Abstract

A strong physical association of indoleacetic acid. 2.4-dichloro-phenoxyacetic acid, indolepropionic acid and indolebutyric acid with lecithin was found which might have physiological significance (regulation, polar mobility). The association is assumed to be mainly due to bonding between the complementary charged groups of the phospholipid and auxin molecules and to specific interaction of the more hydrophobic parts of the molecules. The following interactions were established: Lecithin dissolved in CCl4 moves indoleacetic acid and 2.4-dichloro-phenoxyacetic acid out of an aqueous phase. Cholesterol, long chain fatty acids and amines did not give this interaction with indoleacetic acid and 2.4-dichlorophenoxyacetic acid 4, 5. 1 mole lecithin was found to bind up to 0.8 mole indoleacetic acid. Cephalin and phosphatidylserin exhibit a weaker interaction. Indolepropionic acid and indolebutyric acid were found to compete with indoleacetic acid. There was no effective competition of benzoic acid, phenoxyacetic acid, phenylacetic acid, cholesterol and several fatty aids with indoleacetic acid for the binding sites on the lecithin molecule. 2,4-dichlorophenoxyacetic acid appears to be bound stronger than indoleacetic acid and phenoxyacetic acid. Indoleacetic acid and 2.4-dichlorophenoxyaetic acid were incorporated into swollen lecithin lamellae. Similar interactions are to be expected for other hormones and phospholipids. The lipoprotein structures of cell membranes may be visualized to interact even more specificly with growth hormones than our model system. It is suggested that interaction of hormones with membranes should be considered in theories on regulation. Experiments on ion permeability indicate an influence of indoleacetic acid on cell membranes.