A molecular layer-by-layer (mLbL) deposition process is demonstrated to synthesize conformal coatings of crosslinked polyamide. This process controls the rapid reaction of trimesoyl chloride and m-phenylene diamine, unlike interfacial polymerization techniques which produce rough films and poorly defined network structure. Layer-by-layer polyamide films appear structurally similar to interfacially polymerized films with a linear film growth rate of %0.9 nm per cycle. Films made by mLbL deposition show a 70-fold decrease in surface roughness as compared to a commercial, interfacially polymerized polyamide. Surface chemistry could be controlled based on which reaction step was performed last, leading to amine or carboxylic acid rich surfaces. With the ability to control chemical structure throughout the crosslinked network, this technique provides new routes to build polyamide films and improve analysis techniques for commercial applications such as reverse osmosis membranes.

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Rhodamine‐labelled epidermal growth factor (Rh‐EGF) was shown to bind to A431 cells grown at low density both to a small number of high affinity receptors (KD = 2.8 X 10(‐10) M; fraction of total binding sites approximately 0.12) and also to a large number of low affinity receptors (KD = 4 X 10(‐9) M; fraction of total binding sites approximately 0.88). Measurements of the lateral diffusion of EGF receptors on the cell surface were made using Rh‐EGF and the technique of fluorescence photobleaching recovery. The high affinity receptors (labelled with 1.6 X 10(‐10) M Rh‐EGF, 5% of EGF binding sites occupied) did not show lateral mobility over the temperature range 3 degrees‐37 degrees C. The low affinity receptors (labelled with 2.4 X 10(‐7) M Rh‐EGF, 90% of EGF sites occupied) showed at least 75% fluorescence recovery after photobleaching, and lateral diffusion coefficients of approximately 2 X 10(‐10) cm2/s. These results show that the two populations of EGF receptors defined by binding studies differ in their freedom to diffuse laterally. The observation that the high affinity receptors are immobile indicates that lateral diffusion of receptors, at least over a distance of a few hundred nanometres or more, may not be required for the action of low concentrations of EGF.