Phospholipid Headgroups as Sensors of Electric Charge
In 1839 the anatomist T. Schwann published his “Microscopic Investigations on the Similiarity of Structure and Growth of Animals and Plants” in which he provided the first evidence that animals and plants are composed of the same elements, the cells. The new cell theory immediately led to the question of how the cells could manage to move matter from one cell to the other. Around 1900 the biologist E. Overton investigated the transport rate of more than 300 different organic compounds in animal and plant cells. He observed that all compounds which were easily soluble in oil or similar solvents could move through the living protoplast with high speed whereas other compounds which were easily soluble in water but not in ether, alcohol, or oil migrated only slowly. Based on this selective solubility of plant and animal cells he concluded that the outer surface of the cell was impregnated by a substance which had solubility properties similar to those of a fatty oil. In particular, he suggested that the outer cell layer was composed of a mixture of lecithin and cholesterol 1.
KeywordsCholesterol Permeability Crystallization Glycerol Hexane
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