Properties of Protein Monolayers

Abstract: Publisher Summary There are two methods of affecting spreading of proteins on aqueous surfaces. Hughes and Ridea. Hughes, Fosbinder and Lessig found that solid particles, even of water insoluble proteins, spread very rapidly when carefully placed on the surface. The amount of material spread is determined by a modified Nernst balance. The other method that has several advantages over the solid particle method is to drop on the clean aqueous surface a dilute solution of the protein. In each individual case, the spread areas per unit weight of protein must be demonstrated to be independent of the protein concentration, in the concentration range that is employed. Rideal, Neurath and Gorter find that when a spread protein film is irradiated with ultraviolet light, the film collapses. This collapse is presumably due to fragmentation of the protein molecule by the ultraviolet light with the production of soluble, pressure displaceable material. The nature of the folding of the spread protein as well as the sequence of the amino acid residues in the chain, two problems of great importance to protein chemistry, cannot at the present time be studied by spread film technique.

Abstract: The full-length ZipA protein from Escherichia coli, one of the essential elements of the cell division machinery, was studied in a surface model built as adsorbed monolayers. The interplay between lateral packing and molecular conformation was probed using a combined methodology based on the scaling analysis of the surface pressure isotherms and ellipsometry measurements of the monolayer thickness. The observed behavior is compatible with the one expected for an intrinsically disordered and highly flexible protein that is preferentially structured in a random coil conformation. At low grafting densities, ZipA coils organize in a mushroom-like regime, whereas a coil-to-brush transition occurs on increasing lateral packing. The structural results suggest a functional scenario in which ZipA acts as a flexible tether anchoring bacterial proto-ring elements to the membrane during the earlier stages of division.—Lopez-Montero, I., Lopez-Navajas, P., Mingorance, J., Rivas, G., Velez, M., Vicente, M., Monroy, F. ...

Abstract: 1. 1. The critical gelation area of ovalbumin monolayers was determined over the pH range (0∼11) of the subsolution and was shown to be a maximum at pH 0.2. This result was discussed in connection with the shape of film molecules. 2. 2. The change undergone by ovalbumin solution during aging was followed by a surface rheology technique. 3. 3. Organic additives as spreaders in the spreading solution had a considerable effect on the rheological characteristics of protein monolayers. This fact suggests the formation of organic additive-protein complexes.