Surface properties of valine-gramicidin A at the air-water interface

Ducharme, Daniel; Vaknin, David; Paudler, Michaela; Salesse, Christian; Riegler, Hans; Möhwald, H.

doi:10.1016/s0040-6090(95)08278-6

Cited by 14 publications

(27 citation statements)

References 13 publications

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“…The surface pressure (-A) isotherm of pure VGA at the air-water interface presented in Fig. 1 is in agreement with previously published data (Kemp and Wenner, 1976;Mau et al, 1987;Tournois et al, 1989;Ducharme et al, 1996). A liquid-like phase extends from the onset of the surface pressure (ϳ4.75 nm 2 per molecule) to the characteristic shoulder, which occurs between ϳ12.5 and 15 mN m Ϫ1 (between 2.5 and 1.8 nm 2 per molecule).…”

Section: Surface Pressure X-ray Reflectivity and Thickness Measurementssupporting

confidence: 90%

eSpectroscopic and Structural Properties of Valine Gramicidin A in Monolayers at the Air-Water Interface

Lavoie

Blaudez

Vaknin

et al. 2002

Biophysical Journal

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Monomolecular films of valine gramicidin A (VGA) were investigated in situ at the air-water interface by x-ray reflectivity and x-ray grazing incidence diffraction as well as polarization modulation infrared reflection absorption spectroscopy (PM-IRRAS). These techniques were combined to obtain information on the secondary structure and the orientation of VGA and to characterize the shoulder observed in its pi-A isotherm. The thickness of the film was obtained by x-ray reflectivity, and the secondary structure of VGA was monitored using the frequency position of the amide I band. The PM-IRRAS spectra were compared with the simulated ones to identify the conformation adopted by VGA in monolayer. At large molecular area, VGA shows a disordered secondary structure, whereas at smaller molecular areas, VGA adopts an anti-parallel double-strand intertwined beta(5.6) helical conformation with 30 degrees orientation with respect to the normal with a thickness of 25 A. The interface between bulk water and the VGA monolayer was investigated by x-ray reflectivity as well as by comparing the experimental and the simulated PM-IRRAS spectra on D(2)O and H(2)O, which suggested the presence of oriented water molecules between the bulk and the monolayer.

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Section: Surface Pressure X-ray Reflectivity and Thickness Measurementssupporting

confidence: 90%

eSpectroscopic and Structural Properties of Valine Gramicidin A in Monolayers at the Air-Water Interface

Lavoie

Blaudez

Vaknin

et al. 2002

Biophysical Journal

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“…Pure gramicidin layers were typically examined at lower surface pressures, mainly for two reasons. First, gramicidin films at higher surface pressure are known to be extremely stiff, and the Wilhelmy plate tends to be pushed out of the subphase (Ducharme et al, 1996). Under these conditions the lateral film pressure cannot be measured precisely.…”

Section: Pure Gramicidin Layersmentioning

confidence: 99%

“…The film was compressed to an area per molecule that was known to give the desired film pressure. The corresponding pressure-area isotherms made with a Langmuir-type measuring system were taken from the literature (Ducharme et al, 1996).…”

Section: Pure Gramicidin Layersmentioning

confidence: 99%

Polarization-Modulated FTIR Spectroscopy of Lipid/Gramicidin Monolayers at the Air/Water Interface

Ulrich

Vogel

1999

Biophysical Journal

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Monolayers of gramicidin A, pure and in mixtures with dimyristoylphosphatidylcholine (DMPC), were studied in situ at the air/H2O and air/D2O interfaces by polarization-modulated infrared reflection absorption spectroscopy (PM-IRRAS). Simulations of the entire set of amide I absorption modes were also performed, using complete parameter sets for different conformations based on published normal mode calculations. The structure of gramicidin A in the DMPC monolayer could clearly be assigned to a beta6.3 helix. Quantitative analysis of the amide I bands revealed that film pressures of up to 25-30 mN/m the helix tilt angle from the vertical in the pure gramicidin A layer exceeded 60 degrees. A marked dependence of the peptide orientation on the applied surface pressure was observed for the mixed lipid-peptide monolayers. At low pressure the helix lay flat on the surface, whereas at high pressures the helix was oriented almost parallel to the surface normal.

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“…Compared to the area occupied per monomer (1844 Å 2 ), the area available at point B is much larger. It is reasonable to think that the reorientation of helix bundles creates voids between individual molecules and that these voids cannot immediately be filled up to form a closely packed layer at the air/water interface [9,36]. An important, calculated [37] or observed [38] tilt angle, around 20° for 12‐helix bundles, may result in a large spacing between molecules.…”

Section: Discussionmentioning

confidence: 99%

Molecular organization of the human serotonin transporter at the air/water interface

et al. 2001

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The serotonin transporter (SERT) is the target of several important antidepressant and psychostimulant drugs. It has been shown that under defined conditions, the transporter spread at the air/water interface was able to bind its specific ligands. In this paper, the interfacial organization of the protein has been assessed from dynamic surface pressure and ellipsometric measurements. For areas comprising between 10 400 and 7100 A î 2 /molecule, ellipsometric measurements reveal an important change in the thickness of the SERT film. This change was attributed to the reorientation of the transporter molecules from a horizontal to their natural predictive transmembrane orientation. The thickness of the SERT film at 7100 A î 2 /molecule was found to be approximately equal to 84 A î and coincided well with the theoretical value estimated from the calculations based on the dimensions of K K-helices containing membrane proteins. These data suggest that the three-dimensional arrangement of the SERT may be represented as a box with lengths d z = 83^85 A î and d y or d x = 41^47 A î . ß

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Surface properties of valine-gramicidin A at the air-water interface

Cited by 14 publications

References 13 publications

eSpectroscopic and Structural Properties of Valine Gramicidin A in Monolayers at the Air-Water Interface

eSpectroscopic and Structural Properties of Valine Gramicidin A in Monolayers at the Air-Water Interface

Polarization-Modulated FTIR Spectroscopy of Lipid/Gramicidin Monolayers at the Air/Water Interface

Molecular organization of the human serotonin transporter at the air/water interface

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