Levels of Organization Image Map
Jim became famous for his work on biological membranes. In 1952, he wrote a famous book with his old friend, Hugh Davson, in which they developed a mental model of how membranes were built. Their model grew out of their research and that of others on the transport of materials across capillaries and red blood cell membranes. This model dominated thinking among world scientists for over a decade.

Davson and Jim also developed the idea that proteins associated with membranes could help move certain chemicals across the membrane, which otherwise would not occur. This idea has stood the test of time. See "What We Know" pages on membrane proteins.

Membrane Model ImageWhat was important about the Davson-Danielli membrane model was that though it was not entirely correct, it stimulated other scientists to study the question of how membranes are built. The D-D model correctly viewed the membrane as consisting of two layers of lipid, with their electrically charged head groups facing outward toward the water-based environment both outside and inside of the membrane.

What was wrong with the model was the location of proteins. Proteins were thought to be attached as a thin layer on the inner and outer surfaces of the membrane. Today, we know that proteins float around in the membrane, forming multiple coils that weave in and out of the membrane, with tails of the proteins projecting out on both the outside and inside of the cell.

In one of the great ironies of science, it turns out that what was considered to be wrong has proved to be at least partially right. We now know that some proteins ARE adsorbed on the cell membrane, especially on the inner surface. These interact with the proteins that are coiled within the membrane, and these in turn have regions of the protein that extend outside the cell to act as detectors for chemicals. Think of these outside areas as chemical antennae and the inside areas as a "tuner" that amplifies the chemical signals detected on the outside.

Danielli's contribution was that he got scientists pointed in the right direction - that is, asking the right questions.  Many great discoveries, including several Nobel prizes, developed out of work that was spawned by Jim Danielli.

Sources

1. Stein, W. D. 1987. James Frederic Danielli. The Royal Society. University Press, Cambridge, Great Britain.

2. Davson, H., and Danielli, J. F. 1970. The Permeability of Natural Membranes. Hafner Publishing Company. Darien, Conn. pp. 365.

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