An automated apparatus for interfacial tension measurements by the sessile drop technique

Carlà, Marcello; Cecchini, Rúbens; Bordi, S.

doi:10.1063/1.1142011

Cited by 20 publications

(8 citation statements)

References 12 publications

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“…Measurements have been performed using the drop−shape technique with a sessile drop of about 6 mm diameter. The experimental apparatus, controlled by a microVAX computer, has been described elsewhere …”

Section: Methodsmentioning

confidence: 99%

“…The experimental apparatus, controlled by a microVAX computer, has been described elsewhere. 23 Reagents were Kryptofix 222 (purity > 99%) and NaCl, both from Merck, Suprapur grade; mercury was purified by repeatedly washing in concentrated NaOH and HNO 3 alternatively; water was obtained by a Millipore Milli-Q purifying system fed with spring water with low mineral content. Kryptofix 222 and NaCl were used without any further purification.…”

Section: Methodsmentioning

confidence: 99%

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Adsorption Properties of Cryptand 222 at the Charged Mercury−Solution Interface

1996

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The adsorption of the macrocyclic ligand kryptofix 222 at the mercury−water interface has been studied as a function of the polarization potential and the ligand concentration. An automated apparatus has been used to measure interfacial tension by the drop−shape technique. The relative surface excess and the surface charge density have been obtained, and from these parameters, the molecular packing at the interface and the free energy of adsorption have been calculated. The results show that the macrocyclic ligand strongly adsorbs at the interface in the presence of an intermolecular repulsive electrostatic contribution due to Na+ cations trapped inside the macrocyclic cage. Moreover the adsorption driving force is similar to that reported for the adsorption of aliphatic compounds, i.e., the hydrophobic repulsion of the exposed molecular surfaces.

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Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Adsorption Properties of Cryptand 222 at the Charged Mercury−Solution Interface

1996

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“…The interfacial behavior of DMSO and HMBA was studied at the charged mercury-aqueous solution interface in a described apparatus (13). The interfacial tension y was determined as a function of polarization potential OM and inducer concentration c, at the temperature T = 25°C.…”

Section: Methodsmentioning

confidence: 99%

“…The inducer capability to alter the surface potential was thoroughly analyzed by using an apparatus devised for studying polarized interfaces (13). Both HMBA and DMSO displayed a certain degree of hydrophobic adsorption at the electrode surface, which varied as a function of the charge density, am, with a maximum around -10 lC/cm2 (Fig.…”

Section: Methodsmentioning

confidence: 99%

Polar/apolar compounds induce leukemia cell differentiation by modulating cell-surface potential.

Arcangeli

Carlà

Bene

et al. 1993

Proc. Natl. Acad. Sci. U.S.A.

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The mechanism of action of polar/apolar inducers of cell differentiation, such as dimethyl sulfoxide and hexamethylene-bisacetamide, is still obscure. In this paper evidence is provided that their effects on murine erythroleukemia cells are modulated by various extracellular cations as a precise function of the cation effects on membrane surface potential. The interfacial effects of the inducers were directly measured on the charged electrode, showing that both dimethyl sulfoxide and hexamethylene-bisacetamide, at the effective concentrations for cell differentiation and within the physiological range of charge density, adsorb at the charged surface and produce a potential shift. A linear correlation was found between this shift and the inducer effects on cell differentiation. Besides offering a different interpretation of the mechanism of action of the inducers, these rmdings indicate that surface potential has a signaling function. They may also be relevant to cancer treatments based on tumor-cell commitment to terminal differentiation.Cell fate during embryogenesis and cell culture, as well as tumor progression, can be altered by a heterogeneous class of compounds, known as inducers (1). Of these, a category most widely effective on transformed cell lines and primary malignancies are the so-called polar/apolar inducers (2-6)-for example, dimethyl sulfoxide (DMSO) and hexamethylene-bisacetamide (HMBA). These compounds contain an apolar region linked to one or more polar molecular groups, so that their essential feature is a combination of hydrophobicity and a high dipole moment (5, 6), and their target is the plasma membrane (ref. 7 and references therein). Studies (7) based on the use of lipophilic cations indicated that the electrical potential across the plasma membrane was implicated in leukemia cell commitment to differentiation by DMSO and HMBA. To deepen this observation it was necessary to distinguish the contribution given to the true transmembrane potential (O.) by the resting potential (4r1st) and the surface potentials at the intra-and extracellular side of the plasma membrane (4i and O., respectively). In fact, voltage-dependent macromolecules located within the plasma membrane-for example, the voltage-dependent sodium channels ofexcitable cells-sense and are modulated by the sum (4i -4e) + 4mst = Om. We present evidence that DMSO and HMBA act by modulating the surface potential, indicating a link between this potential and cell fate. This demonstration has potentially far-reaching implications for cell contact and cell-surface adhesion signaling, particularly during embryogenesis (8) and cancer invasiveness (9). These

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“…Interfacial tension measurements were carried out by the sessile drop method using the computerized system and the procedure described in refs and , with a few slight modifications required by the use of Ga instead of Hg. Thus, the Ga sessile drop was extruded from a Teflon tube, rather than from a glass one, since gallium tends to stick to glass walls.…”

Section: Methodsmentioning

confidence: 99%

The Entropy of Formation of the Liquid Gallium−Water Interface

et al. 1999

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The entropy of formation of the interface, S*, between liquid gallium and aqueous solutions of the nonspecifically adsorbed Na 2 SO 4 was calculated from interfacial tension measurements carried out by a wholly computerized sessile drop technique. The advantages of nonisothermal conditions over isothermal conditions for a direct estimate of S* are pointed out on the basis of thermodynamic arguments. The entropy of formation of the inner layer at the gallium|water interface, as estimated at 36°C upon correction for the small diffuselayer contribution, increases monotonically with an increase in the charge density σ M on the metal over the accessible charge range and is about 1 order of magnitude greater than that at the mercury|water interface at 25°C. This difference in behavior is explained on the basis of the notable difference in hydrophilicity between the two metals.

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An automated apparatus for interfacial tension measurements by the sessile drop technique

Cited by 20 publications

References 12 publications

Adsorption Properties of Cryptand 222 at the Charged Mercury−Solution Interface

Adsorption Properties of Cryptand 222 at the Charged Mercury−Solution Interface

Polar/apolar compounds induce leukemia cell differentiation by modulating cell-surface potential.

The Entropy of Formation of the Liquid Gallium−Water Interface

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