The thicknesses of hemoglobin and bovine serum albumin molecules as unimolecular layers adsorbed onto films of barium stearate.

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The following work, which describes a method of measuring one dimension of some protein molecules, is based on the determination of the apparent thickness of a unimolecular layer of globular protein molecules adsorbed from solution onto a metallic slide covered with an optical gauge of barium stearate. Langmuir [1, 2] and Rothen [3] have published a few results obtained by such a technique, but have not exploited the method thoroughly. A complete set of experimental data has been obtained by Clowes [4] on insulin and protamine. He studied the effects of pH and time of exposure on the thickness of layers of protamine and insulin adsorbed onto slides covered with barium stearate and conditioned with uranyl acetate. He found that the pH was responsible for large variations in the thickness of the adsorbed layers and that the thickness of insulin layers adsorbed onto a protamine base was dependent on the concentration of the insulin. Since Clowes found thicknesses as high as 100 A. for protamine and 400 A. for insulin, he was without doubt usually dealing with multilayers.