Davson-Danielli model
Encyclopedia
In 1935, Hugh Davson
and James Danielli
proposed a model of the cell membrane
in which the phospholipid
bilayer
lay between two layers of globular protein
. The phosopholipid bilayer had already been proposed by Gorter and Grendel in 1925, but the Davson–Danielli model's flanking proteinaceous layers were novel and intended to explain Danielli's observations on the surface tension of lipid bilayers. (It is now known that the phospholipid head groups are sufficient to explain the measured surface tension.) The Davson–Danielli model predominated until Singer and Nicolson advanced the fluid mosaic model in 1972. The fluid mosaic model expanded on the Davson–Danielli model by including transmembrane proteins, and eliminated the previously-proposed flanking protein layers that were not well-supported by experimental evidence.
Hugh Davson
Hugh Davson was a 20th century English physiologist who worked on membrane transport and ocular fluids.He attended University College School. He later studied at University College London and took a variety of research posts at institutes such as UCL, and Canada's Dalhousie University...
and James Danielli
James Danielli
James Frederic Danielli was an English biologist.He was famous for research on the structure and the permeability of cell membranes, developing a physical-chemical model in collaboration with the physiologist Hugh Davson. This became known as the Davson-Danielli or "protein sandwich" model...
proposed a model of the cell membrane
Cell membrane
The cell membrane or plasma membrane is a biological membrane that separates the interior of all cells from the outside environment. The cell membrane is selectively permeable to ions and organic molecules and controls the movement of substances in and out of cells. It basically protects the cell...
in which the phospholipid
Phospholipid
Phospholipids are a class of lipids that are a major component of all cell membranes as they can form lipid bilayers. Most phospholipids contain a diglyceride, a phosphate group, and a simple organic molecule such as choline; one exception to this rule is sphingomyelin, which is derived from...
bilayer
Bilayer
A bilayer is a double layer of closely packed atoms or molecules. The properties of bilayers are studied in condensed matter physics, often in the context of semiconductor devices, where two distinct materials are united to form junctions ....
lay between two layers of globular protein
Protein
Proteins are biochemical compounds consisting of one or more polypeptides typically folded into a globular or fibrous form, facilitating a biological function. A polypeptide is a single linear polymer chain of amino acids bonded together by peptide bonds between the carboxyl and amino groups of...
. The phosopholipid bilayer had already been proposed by Gorter and Grendel in 1925, but the Davson–Danielli model's flanking proteinaceous layers were novel and intended to explain Danielli's observations on the surface tension of lipid bilayers. (It is now known that the phospholipid head groups are sufficient to explain the measured surface tension.) The Davson–Danielli model predominated until Singer and Nicolson advanced the fluid mosaic model in 1972. The fluid mosaic model expanded on the Davson–Danielli model by including transmembrane proteins, and eliminated the previously-proposed flanking protein layers that were not well-supported by experimental evidence.