User:Daljaberz/sandbox

The Davson and Danielli Model with backup from Robertson
Following the proposal of Gorter and Grendel, inevitable questions arose about the clarity of having just a simple lipid bilayer as a membrane. Their model wasn’t suitable to answer the relations of surface tension, permeability, and the electric resistance of membranes. Therefore, physiologist Hugh Davson and biologist James Danielli suggested that membranes indeed do have proteins. The existence of these “membrane proteins” would explain that which couldn’t be answered by the Gorter and Grendel model. In 1935, Davson and Danielli proposed that biological membranes are made up of lipid bilayers which are coated on both sides with thin sheets of protein. They simplified their model into the “pauci-molecular” theory. The theory declared that all biological membranes have a “lipoid” center surrounded by monolayers of lipid and are covered by protein monolayers. In short, their model was illustrated as a “sandwich” consisting of protein-lipid-protein. The Davson and Danielli model made way for the rudimentary understanding of cell membranes, and stressed the importance of proteins in biological membranes.

By the 1950’s, cell biologist verified the existence of plasma membranes due to the creation of the electron microscope (which accounted for higher resolutions). J. David Robertson used this tool (electron microscopy) to propose the unit membrane model. Basically, he suggested that all cellular membranes share a similar underlying structure, the unit membrane. Using heavy metal staining, Robertson’s proposal also seemed to agree instantaneously with the Davson and Danielli model. According to the trilaminar pattern of the cellular membrane viewed by J. David, he suggested that the membranes consist of a lipid bilayer covered on both surfaces with thin sheets of proteins. This suggestion gave great support to the proposal of Hugh Davson and James Danielli. However, even with Robertson’s substantiation great complications came with the Davson and Danielli model. One main complication being, that the membrane proteins studied were mainly globular and wouldn’t fit into the model’s claim of thin sheets of proteins. Along with these arising complications of the Davson and Danelli model, interest in finding new ways of membrane organization stimulated and made way for the Fluid Mosaic model which was proposed in 1972.