Membrane

Events

Membrane contains lipid

1895

The earliest intimations that the membrane contained lipid came from the work of the Overton, who discovered that lipid-soluble molecules penetrated into cells more easily

Lipid molecules are amiphiphilic

1917

Langmuir showed that some lipid molecules were amiphiphilic in having a polar head and non-polar carbon chain

Bilayer Concept

1925

Gorter and Grendel Experiment found that measured minimal area of lipids compressed on a monolayer trough was twice the value of the total surface area of red blood cells

Membrane is fluid

Approx. 1930

Chambers and Kopac showed that two droplets of oil on two areas of an egg membrane moved relative to one another when the seawater was agitated, indicating that the membrane was fluid

Polar membrane channels

1943

Danielli & Davson presented a diagram showing hydrophobic amino-acid side-chains penetrating between lipid head-groups, between carbon chains of lipid molecules, which indicated transmembrane polypeptide chains as polar transmembrane channels

Electron Micrograph developments

1950

The introduction of potassium permanganate as a fixing agent and epoxy resins as embedding materials led to visualisation of the cell membrane as a triple-layered structure

Freeze-fracture-etch electron microscopy develops

1957

Introduced by Steere in 1957, FFE electron microscopyproved crtical in future developments of understanding

Experiments to show protein location

1971 - 1972

Chemical labeling, and later, proteolytic disscetion experiments resulted in the location of proteins as peripheral or integral.

Intramembrane Particles are protein-based

1971

Branton found that IMPS are reduced in membranes treated with proteases

Fluid Mosaic Model

1972

Singer & Nicholson propose new membrane paradigm; inner and outer surfaces of membrane as largely naked lipid with protein macromolecules embedded in the bilayer in an iceberg like fashion

Purple Membrane investiagtion

1974

Patches of 'purple membrane' contain proteins which act as 'proton pumps' which help maintain the pH of the cell

Membrane regulates cell conformation

1978

Tilney and Detmers suggest glycoproteins might interact with ATP to regulate the shape of the cell