|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.
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
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
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
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.