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Journal ArticleDOI

Cohesive force between the CH2 groups of protein molecules at oil/water interface

01 Jun 1972-Vol. 250, Iss: 6, pp 615-616
About: The article was published on 1972-06-01. It has received 2 citations till now.
Citations
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Book ChapterDOI
TL;DR: In this article, a state equation for an ionized monolayer and its corresponding adsorption isotherm for one-one valent long-chain electrolytes taking account of the interaction between amphiphilic ions are proposed.
Abstract: A state equation for an ionized monolayer and its corresponding adsorption isotherm for one-one valent long-chain electrolytes taking account of the interaction between amphiphilic ions are proposed. The validity of the equations is demonstrated using adsorbed layers of cetyl trimethyl ammonium bromide (CTAB) on the basis of high precision (±0,02 mJ·m−2) tensiometric measurements at the water-air and water-octane interfaces at 303–343 K. Analysis of the values measured for interfacial tension and ionisation potential has shown for both interfaces the existence of three regions characterized by different extents to which the interactions between adsorbed amphiphilic ions are manifested. The region of low surface occupancy, θ≧∼ 0,1 (ideal behaviour of monolayer), the region ∼0,1 ∼0,7 where the layer approaches the condensed state (a 0 increases monotonously) were examined. An important role is shown to be played by the hydrophobic interactions between the segments of hydrocarbon chains of adsorbed cetyl trimethyl ammonium (CTA+) ions immersed into water.

15 citations

Journal ArticleDOI
TL;DR: In this article, another expression for the monolayer of the adsorbed ionic surfactant (2D layer) is proposed, which divides the total effect into the electrostatic and nonelectrostatic contributions.
Abstract: The Davies equation and relative expressions belong to the most popular tools for describing the equilibrium state of ionic surfactants on the water–air or water–hydrocarbon interface. During over half a century, this equation was repeatedly discussed and modified and various attempts of its derivation/reconsideration were proposed for both insoluble and soluble monolayers. In this paper, the corresponding publications are regarded. Basing on the previously derived modification of the fundamental Gibbs equation [Surface Eng. 50 (2014) 173–182; https://doi.org/10.3103/S1068375514020100.], another expression for the monolayer of the adsorbed ionic surfactant (2D layer) is proposed, which implies dividing the total effect into the electrostatic and non-electrostatic contributions. The dependence of the surface pressure, П, on the area per adsorbed amphiphilic ion in the interface, A , excluded area, A 0 , and the electrical potential Ψ of the compact monolayer against the bulk aqueous phase is obtained taking into account the degree of counter ion binding, β , and cohesion. In the following equation, the second term of the right-hand side is caused by the electrostatic energy of transfer of the charged amphiphile from the bulk to the monolayer, whereas the third one represents the electrostatic contribution to the surface pressure: Π + Π c = − k T ∫ ∞ A ( 1 + β ) ( A − A 0 ) − 2 d A + ∫ 0 Ψ ( 1 + β ) z 2 e A − 1 d Ψ + ∫ 0 Ψ ( 1 − β ) z 2 e A − 1 d Ψ , where k , T , and e have their usual meaning. In particular, in its limited form, for β = 0 and neglecting the cohesion term, Π c , the equation of state is as follows: Π = k T ( A − A 0 ) − 1 + 2 ∫ 0 Ψ e A − 1 d Ψ . This relation differs from the common Davis equation by the coefficient "2" in the last rhs term. Some limiting cases are considered, and an attempt to adapt the equation to experimental data is made.

1 citations

References
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Journal ArticleDOI
TL;DR: In this article, a new equation has been derived for air-water films by taking cohesive energy as well as electrical repulsion into account, and this equation is compared with recent experimental results.
Abstract: The force-area characteristics of charged films adsorbed at the air-water surface should not be compared with the previously published theoretical treatment of Davies—this treatment applies only to charged films at the oil-water surface. By taking cohesive energy as well as electrical repulsion into account, a new equation has been derived for air-water films. This equation is compared with recent experimental results.

63 citations

Journal ArticleDOI
TL;DR: In this article, the van der Waals equation for cohesive surface pressure for the monolayer of long-chain quarternary ammonium ions has been found to vary linearly with the inverse square of the area per molecule in the lower range of surface concentration.
Abstract: The cohesive surface pressure for the monolayer of long-chain quarternary ammonium ions has been found to vary linearly with the inverse square of the area per molecule in the lower range of surface concentration. This linear behavior has been explained on the basis of the van der Waals equation for cohesive pressure applied to the surface phase of definite thickness. From the comparison of values of the van der Waals constant for attraction in two and three dimensions, the thickness of the surface phase containing an ionized monolayer has been estimated. At the region of higher surface concentration, the adsorbed long-chain ions have been found to aggregate forming surface micelles. The aggregation number of these micelles has been estimated.

24 citations

Journal ArticleDOI
TL;DR: In this article, a newly synthesized polypeptide, poly-1:1:2: lysine-glutamicacid-leucine has been studied in monomolecular films, and it is shown that dissociation of the polymer at the interfaces air/10 -2 N acid and oil/water does not occur; the effects apparently suggesting such dissociation are entirely due to variations in the type of quasi-lattice of the interface.
Abstract: A newly synthesized polypeptide, poly-1:1:2: lysine-glutamicacid-leucine has been studied in monomolecular films. In many respects it behaves analogously to natural proteins, as is to be expected from its composition. The controversial issues concerning the interfacial dissociation of proteins are examined by comparison with results from this poly-amino-acid. By an improvement of technique to reach the requisite low pressures, it is shown that dissociation of the polymer at the interfaces air/10 -2 N acid and oil/water does not occur; the effects apparently suggesting such dissociation are entirely due to variations in the type of quasi-lattice of the interface. Statistical equations of the Flory and Huggins types, based on a two dimensional quasi-lattice theory, are tested using the copolymer; the sites in the surface are shown to be occupied in a non-random manner. The complete surface equation of state for charged macromolecules is derived, including intermolecular and intramolecular electrical repulsion.

11 citations