Abstract
The structure of lysozyme monolayers was investigated by the measurements of surface pressure, surface viscosity and surface potential. Following four distinct results were obtained.
(1) The reproducibility of the surface potential-area curve of lysozyme was very high at larger areas. The region in which film potentials fluctuate violently appeared as the film was compressed. Further compression beyond the area from which the surface viscosities began to rise steeply made the reproducibilities of the potentials very high. These facts are related to the aggregation state of lysozyme molecules. Therefore, the change in the state of lysozyme monolayer at its isoelectric point might be inferred from the curve of mean deviations of the observed ΔV values plotted against areas.
(2) The curves of surface potentials plotted against pressures were represented by a single curve and did not depend on the spreading solutions. The assumptions for the structure of lysozyme monolayers described in Part II were substantiated from this fact.
(3) The presence of sodium sulfite affects the F-A, η-A and ΔV-A curves of lysozyme monolayer. The reduction of intermolecular disulfide bonds were shown from various observations. When lysozyme was reduced with sulfite in spreading solution, the monolayers spread from it had very high viscosities from larger areas. The formation of strong intermolecular crosslinks including disulfide was suggested in this case.
(4) The presence of sodium sulfite in the substrate had no effect on the viscosities of ovalbumin monolayers. In this case the monolayers were spread from a solution of ovalbumin in 8M urea. Never-theless, the evidence of the formation of inter- or intra-molecular disulfide bonds was not obtained.
The author wishes to express his sincere thanks to Prof. T. Isemura for his kind guidance throughout the present work and to Prof. S. Akabori, Mr. K. Ohno and Mr. I. Ha runa in the Faculty of Science of Osaka University who supplied the valuable samples of lysozyme and ovalbumin.
