Adsorption of Lysozyme and Methylated Lysozyme at the Air−Water Interface:  An X-ray Reflectivity Study

Postel, Caroline; Abillon, O.

doi:10.1021/la980002l

Cited by 8 publications

(3 citation statements)

References 17 publications

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“…These authors used a one-layer model to find the protein layer thickness and found no evidence of extensive unfolding that would change the protein layer thickness. The trends reported by Lu et al are corroborated by Postel et al, who used X-ray reflectivity to measure the surface concentrations of lysozyme after 24 h periods at pH 6.9, I = 0.1 M, and found that the protein remains side-on and roughly constant for 7.6 × 10 -4 to 10 -2 wt %. Postel et al used similar conditions as did Hunter et al but did not correct their bulk concentration for depletion by adsorption to the interface or sides of their container.…”

Section: Discussionmentioning

confidence: 60%

Evidence that the Induction Time in the Surface Pressure Evolution of Lysozyme Solutions Is Caused by a Surface Phase Transition

2000

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Induction periods have been reported in the surface pressure evolution of a wide variety of proteins. In this work, this induction period is shown to be caused by a first-order phase change from a surface gaseous to a liquid-expanded state as the protein lysozyme adsorbs and decreases the mean area per molecule. The evolution of this transition is studied using concomitant fluorescence microscopy and surface pressure measurements. The fluorescent images are obtained by using spread films of the dye NBD-HDA at the air-liquid interface. This dye fluoresces when in contact with hydrophobic moieties and is quenched when in contact with water. The hydrophobic liquid-expanded domains therefore appear bright on a dark background. Lysozyme initially adsorbs to establish a surface gaseous phase, and the interface appears dark. The surface tension is fairly insensitive to changes in area per molecule in this state. Once the adsorbed concentration of lysozyme reaches the surface gaseous binodal, protein interactions drive a first-order phase change. Domains of liquid expanded phase grow at the interface at the expense of the surface gaseous phase. During this phase change, the surface tension remains constant. Only after the interface is covered in the bright, liquid-expanded phase does the surface tension decrease from the clean interface value. These results are discussed in terms of the surface coverage and orientation of lysozyme.

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Section: Discussionmentioning

confidence: 60%

Evidence that the Induction Time in the Surface Pressure Evolution of Lysozyme Solutions Is Caused by a Surface Phase Transition

2000

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“…The setup used for measurements of x-ray specular reflectivity of liquid surfaces was described elsewhere [17]. The characteristics of the x-ray beam are 0.154 nm for the wavelength , about 2 ϫ 10 6 photons per second for the intensity, 8 mm for the horizontal width w, and 50 m for the height e. As the x-ray reflectivity is a function of the vertical profile of the mean electron density, it gives information on the molecular packing.…”

Section: Methodsmentioning

confidence: 99%

Assembling and compressing a semifluorinated alkane monolayer on a hydrophobic surface: Structural and dielectric properties

Abed¹,

Ionov²,

Daoud³

et al. 2004

Phys. Rev. E

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We investigate the dynamic behavior upon lateral compression of a semifluorinated alkane F (CF2)8(CH2)18H (denoted F8H18), spread on the hydrophobic top of a suitable amphiphilic monolayer: namely, a natural alpha-helix alamethicin peptide (alam). We show, in particular, the formation of an asymmetric flat bilayer by compressing at the air-water interface a mixed Langmuir film made of F8H18 and alam. The particular chemical structure of F8H18 , the suitable structure of the underlying alam monolayer and its collapse properties, allow for a continuous compression of the upper F8H18 monolayer while the density of the lower alam monolayer remains constant. Combining grazing incidence x-ray reflectivity, surface potential, and atomic force microscopy data allow for the determination of the orientation and dielectric constant of the upper F8H18 monolayer.

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“…Thus, black films that are simple, freestanding bilayer systems involving most of the basic physical interactions appear to be very good models for the study of some specific interactions of biological membranes (Sentenac and Benattar, 1998). Few papers have reported attempts to form black films that include proteins, and these only concern microfilms of pure proteins (Musselwhite and Kitchener, 1967;Clark et al, 1990;Marinova et al, 1997;Postel and Abillon, 1998). Where microscopic CBF and NBF have been obtained, their structures were found to be bilayers of denatured proteins, more complex multilayer films, or thick films.…”

Section: Introductionmentioning

confidence: 99%

How to Control the Molecular Architecture of a Monolayer of Proteins Supported by a Lipid Bilayer

Petkova¹,

Benattar

Nedyalkov³

2002

Biophysical Journal

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In this work, we report the spontaneous formation of a new structure composed of two lipid layers surrounding a dense monolayer of soluble proteins (lysozyme). We extend a process, initially discovered with nonionic surfactants to phospholipids (DMPC and DOPC). The motor of the protein insertion process is the difference between the protein chemical potential in the solution and in the freshly formed Newton black film (NBF). This process is completely controlled by adjusting the protein chemical potential in the solution. By means of x-ray reflectivity, we follow the evolution of the freestanding sandwich structure until a stable equilibrium state is reached. Depending on the lipid concentration with respect to the protein concentration, we observe two different behaviors of the film leading to the formation of such unique structure: at the highest lipid concentration, the usual protein diffusion into the NBF, and, at the lowest lipid concentration, the spontaneous formation of a sandwich structure immediately obtained after the drainage. Finally, we show that the insertion process is reversible, because, if the lipid concentration varies in the bulk solution, a "deswelling" of the film can be observed.

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Adsorption of Lysozyme and Methylated Lysozyme at the Air−Water Interface: An X-ray Reflectivity Study

Cited by 8 publications

References 17 publications

Evidence that the Induction Time in the Surface Pressure Evolution of Lysozyme Solutions Is Caused by a Surface Phase Transition

Evidence that the Induction Time in the Surface Pressure Evolution of Lysozyme Solutions Is Caused by a Surface Phase Transition

Assembling and compressing a semifluorinated alkane monolayer on a hydrophobic surface: Structural and dielectric properties

How to Control the Molecular Architecture of a Monolayer of Proteins Supported by a Lipid Bilayer

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