Model calculations of Langmuir monolayers: Pressure effects on tilting behavior of idealized amphiphiles

Swanson, David; Hardy, Robert J.; Eckhardt, Craig J.

doi:10.1063/1.471923

Cited by 7 publications

(4 citation statements)

References 19 publications

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“…Tilting is attributed to a balance of forces acting to optimize van der Waals attractive interactions between alkyl chains and interfacial area of the molecules (Kitaigorodskii, 1961). Theories that emerge from such considerations suggest that the tilt angles must vary with chain length (Safran et al, 1986;Kaganer et al, 1993;Swanson et al, 1996). The a angles determined within the observed uncertainties in the current study (Table 2) suggest that for the longest member in this series, C24, the chains are oriented perpendicular to the mirror surface.…”

Section: Zinc Label Distributionmentioning

confidence: 53%

Spatial resolution of the variable-period x-ray standing-wave method as applied to model membranes

Itri¹,

Zhang²,

Caffrey³

1997

Biophysical Journal

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A series of model membranes as Langmuir-Blodgett (LB) films composed of long-chain zinc alkanoates (saturated fatty acid salts) was used to evaluate the spatial resolution of the variable-period x-ray standing-wave (XSW) technique. The chain length dependence of the zinc mean position (z) above the supporting substrate demonstrates that it is possible to detect differences in (z) of 1-2 A. Thus 1-2 A is the spatial resolution of the method in the current application. The data show that the chain tilt angle is chain length dependent, varying from 40 degrees to 0 degrees for alkanoates 18 and 24 carbon atoms long, respectively. The spread about the mean position of the zinc in the film, sigma(in), was found to be independent of chain length at 10.0 A for all members of the series. Sigma(in) was shown to be insensitive to the presence of a "spacer" omega-tricosenoic acid (omegaTA) bilayer placed between the zinc alkanoate LB film and the coated gold mirror. However, an overlayer of omegaTA sharpened the zinc ion distribution and lowered the chain tilt angle. This study provides important information regarding sample composition and constitution that facilitates membrane structure determination by XSWs.

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Section: Zinc Label Distributionmentioning

confidence: 53%

Spatial resolution of the variable-period x-ray standing-wave method as applied to model membranes

Itri¹,

Zhang²,

Caffrey³

1997

Biophysical Journal

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“…Models of cylindrical rods were considered by Safran, Robbins, and Garoff (1986), Cai andRice (1990, 1992), Kaganer, Osipov, and Peterson (1993), Balashov and Krylov (1994), Shin and Rice (1994), Schmid, Johannsmann, and Halperin (1996), Wang and Gong (1996), and Schmid and Lange (1997). Swanson, Hardy, and Eckhardt (1996) studied a closely related model of ''beaded strings.'' We will discuss first the common qualitative picture of the tilting phase transition, which follows from these papers, and then mention the differences between particular models.…”

Section: A Tilting Transitionsmentioning

confidence: 99%

Structure and phase transitions in Langmuir monolayers

1999

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Lipid monolayers on the surface of water have been studied for over a hundred years, but in the last decade there has been a dramatic evolution in our understanding of the structures and phase transitions of these systems, driven by new experimental techniques and theoretical advances. In this review, dense monolayers of simple lipids are described in detail, including structures revealed by x-ray-diffraction experiments, computer simulations, molecular models, and a phenomenological theory of phase transitions. The effects of chirality and the structures of phospholipid monolayers are considered. Open questions and possible approaches to finding answers are discussed.[S0034-6861(99)00203-2] CONTENTS 815

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“…Neglecting translational motion and simplifying head−head and head−solvent interactions, these schemes prove to be an inadequate tool for description of fluid phases. The more realistic model of “beaded strings” provides more detailed structural information, e.g., the relationship between the molecular geometry and the experimentally observable tilting behavior …”

Section: Introductionmentioning

confidence: 99%

“…The more realistic model of "beaded strings" provides more detailed structural information, e.g., the relationship between the molecular geometry and the experimentally observable tilting behavior. 36 The road to the atomistic approach required the development of methods allowing adequate representation of inter-and intramolecular interactions in large systems within reasonable computational time limits. This instigated the proliferation of all-atom force fields tailored for specific or general applications.…”

Section: Introductionmentioning

confidence: 99%

Dielectric Properties Tangential to the Interface in Model Insoluble Monolayers: Theoretical Assessment

et al. 2008

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Studies of insoluble monolayers built of phospholipids and various long-chained fatty acids or their glycerin esters are the major source for what is currently known about the relationship between monolayer composition and physicochemical properties. The surface pressure, dipole moment, dielectric permittivity, polarizability, refractivity, and other electrical and optical features are governed by the surfactant structural specificity and solvent organization at the microscopic level. To provide insight into the atomistic details of the interfacial structure, model monolayers at the air/water interface of two distinctly different in composition and isotherm profile surfactants are investigated by means of molecular dynamics all-atom simulations. Analysis of the computational results allows the estimation of empirically unattainable quantities such as tangential (di)electric properties, their decomposition to surfactant and water contributions, and their relationship with the changes in interfacial molecular organization at different surface concentrations. The employed theoretical approach provides a comprehensive description of interfacial phenomena at the molecular level where the traditional phenomenological investigations are ineffective.

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Model calculations of Langmuir monolayers: Pressure effects on tilting behavior of idealized amphiphiles

Cited by 7 publications

References 19 publications

Spatial resolution of the variable-period x-ray standing-wave method as applied to model membranes

Spatial resolution of the variable-period x-ray standing-wave method as applied to model membranes

Structure and phase transitions in Langmuir monolayers

Dielectric Properties Tangential to the Interface in Model Insoluble Monolayers: Theoretical Assessment

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