9: Early History of Fluid Membranes
In my laboratory the most interesting experiments dealt with the application of spin labels to membranes. At the time of our first work little or nothing was known about the “fluidity” of cell membranes. I cite an example of this state of knowledge in 1968. In 1968 and 1969 Wayne Hubble and I wrote two little papers on the paramagnetic resonance spectra of two types of spin labels in cell membranes and lipid bilayers. From these studies we concluded that cell membranes were in a bilayer fluid-like state. See (122, 129). Wayne and I then attended a Gordon Conference in 1968 and spoke about the fluidity of cell membranes. Jon Singer presented a model of membranes that, as I recall, was a jumble of protein chain and hydrocarbon chains. There was no suggestion of liquid like properties.
On the last day of this meeting Wayne Hubbell, Jon Singer and I sat down for lunch together. And most remarkably Singer opposed the idea of a fluid model for membranes!
I sketched a crude, speculative model of a globular protein in a fluid bilayer membrane in 1970 (133). (Unfortunately I made the mistake of including cholesterol in the membrane and referring to the membrane as a bacterial cell membrane. Only some mycoplasma contain cholesterol; bacteria do not.)
The famous fluid mosaic model of membranes was published in 1972. I cannot detract from Singer’s prescient fluid mosaic model for membranes, but he clearly was not thinking along those lines at the time of our 1968 meeting. Nor as far as I know was anyone else. The definitive paper on the diffusion of rhodopsin in the rod outer segment membrane was published in 1974. This came as little surprise to my lab that had by then made definitive measurements of the diffusion in lipid bilayers and had solid evidence for a bilayer structure in cell membranes based on the dynamics and orientation of amphiphilic spin labels.