Danielli, James Frederic (1911–1984)

British cell biologist who hypothesized that the molecular structure of the cell membrane was a sandwich of two layers of proteins. In 1943 Danielli and Hugh Davson published their seminal theory on transport of substances across cell membranes in The Permeability of Natural Membranes. Their work provided a framework for future physiologists and cell biologists working on the role of the membrane in different cellular activities.

Cell membranes Danielli's major work was on the structure and physical properties of cell membranes. With Davson he proposed that the cell membrane was a sandwich of two juxtaposed phospholipid (lipid that contain a phosphate group) layers between two layers of globular proteins (proteins that have a globular three-dimensional structure). Phospholipids are amphipathic, that is they have both hydrophobic (water-hating) and hydrophilic (water-loving) regions. In the Davson–Danielli model, the hydrophobic parts of the phospholipid molecules are on the inside of a bilayer, while the hydrophilic parts form the outsides of the membrane.

In the 1950s, cell membranes were imaged using the electron microscope and it was revealed that they were too thin to possess coatings of globular proteins, as suggested by Danielli and Davson. Staining cell membranes with heavy metals, however, revealed a structure consistent with Danielli and Davson's proposed phospholipid bilayer; in 1972, Singer and William Nicholson revised the Davson–Danielli model to include proteins that spanned the membrane rather than existing as layers of protein on either side.

Life Danielli was born in London and graduated with a BSc in chemistry from the University of London. After finishing his PhD, he worked as a postdoctoral scientist at Princeton University in the USA and then at Cambridge University, the Marine Biological Associations laboratory in Plymouth, and the Royal Cancer Hospital in London, before being appointed professor of zoology at Kings College, London 1948. In the mid-1950s he moved to Buffalo State University in New York, where he remained until his retirement in 1980.