Asymmetric Partitioning of Anions in Lysozyme Dispersions

a b s t r a c tHofmeister, specific ion effects, hydration and van der Waals forces at and between interfaces are factors that determine curvature and microstructure in self assembled aggregates of surfactants and lipids; and in microemulsions. Lipid and surfactant head group interactions and between aggregates vary enormously and are highly specific. They act on the hydrophilic side of a bilayer, micelle or other self assembled aggregate. It is only over the last three decades that the origin of Hofmeister effects has become generally understood. Knowledge of their systematics now provides much flexibility in designing nanostructured fluids.The other side of the coin involves equally specific forces. These (opposing) forces work on the hydrophobic side of amphiphilic interfaces. They are due to the interaction of hydrocarbons and other "oils" with hydrophobic tails of surfactants and lipids. The specificity of oleophilic solutes in microemulsions and lipid membranes provides a counterpoint to Hofmeister effects and hydration. Together with global packing constraints these effects determine microstructure.Another factor that has hardly been recognised is the role of dissolved gas. This introduces further, qualitative changes in forces that prescribe microstructure.The systematics of these effects and their interplay are elucidated. Awareness of these competing factors facilitates formulation of self assembled nanostructured fluids. New and predictable geometries that emerge naturally provide insights into a variety of biological phenomena like anaesthetic and pheromone action and transmission of the nervous impulse (see Part 2).

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“…Revisiting the problem recently, two of us showed that in a finite volume system ion specific partitioning did occur [46,119].…”

Section: Discussionmentioning

confidence: 99%

Two sides of the coin. Part 1. Lipid and surfactant self-assembly revisited

Ninham

Larsson

Nostro

2017

Colloids and Surfaces B: Biointerfaces

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“…Unless otherwise stated, all potentials reported here are referenced to the SHE (E°' SHE = E°' Ag/AgCl + 0.204 V at 20 °C). The working electrode was placed in the second compartment, which was 25 comprised of a 10 mL cell with a heating jacket connected to a water bath (Lauda ecoline003). Each value of E°' represents an average of 3 ± 1 data points.…”

Section: Methodsmentioning

confidence: 99%

“…Specific ion effects were examined at 25 an ionic concentration of 200 mM, a concentration reasonably close to that where specific ion effects are observed but sufficiently low to provide an observable faradaic response. Plots of peak current for a range of anions (Fig.…”

Section: Specific Ion Effects On Peak Current Of Cyt Cmentioning

confidence: 99%

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Specific ion effects on the electrochemical properties of cytochrome c

Medda

Salis

Magner

2012

Phys. Chem. Chem. Phys.

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The range of salts used as supporting electrolytes in electrochemical studies of redox proteins and enzymes 5 varies widely, with the choice of electrolyte relying on the assumption that the electrolyte used does not affect the electrochemical properties of the proteins and enzymes under investigation. Examination of the electrochemical properties of the redox protein cytochrome c (cyt c) at a 4,4'-bipyridyl modified gold electrode demonstrates that both the redox potential (E°') and the faradaic current are influenced by the nature of the electrolyte used, in a manner explained primarily by Hofmeister effects. The faradaic peak 10 currents display an atypical trend on switching from kosmotropic to chaotropic anions, with a maximum current observed in the presence of Cl -. For a series of cations, the peak current increased in the sequence;

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“…Even though they are ubiquitous in the physical, chemical and biological literature, their origin is still contested 1-7 and has been recently brought to the forefront of research [8][9][10][11][12][13][14][15][16][17][18][19] . New work in this area may break down barriers between physics and biology 9 .…”

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confidence: 99%

Strong non-classical induction forces in ion-surface interactions: General origin of Hofmeister effects

Liu

et al. 2014

Sci Rep

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Hofmeister effects continue to defy all-encompassing theories, and their origin is still a matter of debate. We observed strong Hofmeister effects in Ca 21 /Na 1 exchange on a permanently charged surface over a wide range of ionic strengths. They could not be attributed to dispersion forces, classical induction forces, ionic size, or hydration effects. We demonstrated that another stronger force was active in the ion-surface interactions, and which would create Hofmeister effects in general. The strength of this force was up to 10 4 times that of the classical induction force, and could be comparable to the Coulomb force. Coulomb, dispersion and hydration effects appeared to be interwined to affect the force. The presence of the observed strong non-classical induction force implied that energies of non-valence electrons of ions/atoms at the interface might be heavily underestimated in current theories, and possibly just those underestimated energies of non-valence electrons determined Hofmeister effects. Hofmeister effects, also known as specific ion effects, were observed over 120 years ago. Even though they are ubiquitous in the physical, chemical and biological literature, their origin is still contested 1-7 and has been recently brought to the forefront of research [8][9][10][11][12][13][14][15][16][17][18][19] . New work in this area may break down barriers between physics and biology 9 . Ionic sizes, hydration, quantum fluctuations (or dispersion forces) 3,4,8 , and surface charges 1,2 are crucial in Hofmeister effects. Nano-scale surfaces and colloidal particles (e.g., DNA, proteins, cells, bacteria, metal oxides, and clay) are usually strongly charged in aqueous solution, and the sign of the charge or the charge number for biological macromolecules will be dependent on pH and ionic strength 20 . In classical theory, the surface charges can set up a strong electric field extending from the surface to several nanometers in solution. Typical surface charge densities and their corresponding electric field strengths include: (1) . For proteins, surface charge density measurements are primarily based on zeta potentials; therefore, they would be equal to the charge density at the shear plane, which is possibly much lower than the charge density at the surface [27][28][29] , especially when considering the strong surface hydration force [30][31][32] . At the shear plane, the charge density could reach 0.02-0.35 C/m 2 [33][34][35] , with an electric field of 10 7 -10 8 V/m. Therefore, it is reasonable to expect electric field strengths .10 8 V/m at protein surfaces in aqueous solutions. However, in those calculations, adsorbed counter-ions near the surface are treated as point charges. If their ionic size were taken into account, then the electric field near the surface would be much greater than 10 8 V/ m. This is because the finite size of counter ions could weaken their screening effect, as compared with point charges.Noah-Vanhoucke and Geissler found that, the persistence of electric field in the space near ...

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Asymmetric Partitioning of Anions in Lysozyme Dispersions

Cited by 40 publications

References 70 publications

Two sides of the coin. Part 1. Lipid and surfactant self-assembly revisited

Two sides of the coin. Part 1. Lipid and surfactant self-assembly revisited

Specific ion effects on the electrochemical properties of cytochrome c

Strong non-classical induction forces in ion-surface interactions: General origin of Hofmeister effects

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