0000000000266058

AUTHOR

Daniel Ducharme

Ellipsometric study of the physical states of phosphatidylcholines at the air-water interface

Etude des couches monomoleculaires de dimyristoylphosphatidylcholine, de dipalmitoylphosphatidylcholine, de distearoyl phosphatidylcholine, de diarachidoylphosphatidylcholine a l'interface air/eau

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

Abstract Fluorescence microscopy, X-ray reflectivity and ellipsometry have been applied to the study of a monolayer of valine-gramicidin A (VGA) at the air-water interface to obtain insight into the conformation and orientation of VGA, and to clarify the shoulder observed in its π - A curve (12.5–16 mN m −1 , 240 – 175 A 2 molecule −1 ). At low molecular areas, the X-ray reflectivities are consistent with formation of a single layer of tubular-shaped dimers. Fluorescence microscopy yielded homogeneous pictures suggesting that on the macroscopic scale the shoulder cannot be attributed to domain formation. Thicknesses calculated from the ellipsometric isotherm are consistent with the X-ray da…

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Optical measurements of an acylated azacrown at the air-water interface

In this study, a cyclame derivative bearing four aliphatic chain substituents shows, like many amphiphiles, solid-condensed as well as liquid-expanded phases. In contrast to the classical amphiphiles, the onset of its phase transition is characterized by a bump-like shape whose amplitude is a function of the compression speed. Ellipsometry which is very sensitive to the monolayer physical state changes, and fluorescence microscopy which has contributed significantly to the understanding of the phenomena occurring in the phase transition region have been used to investigate the monolayer behavior of this compound. This study shows that in the liquid-expanded state, the film is homogeneous an…

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