TITLE:
MorphologicaObservation of Specific Condensation Effect of Cholesterol on Dipalmitoyl Phosphatidyl Choline (DPPC) Monolayer by Dropping Method
AUTHORS:
Takashi Yokoyama, Daisuke Yoshida, Hiroya Mori, Masaya Okabe, Zameer Shervani, Keijiro Taga, Yasushi Yamamoto, Ayumi Sumino, Takehisa Dewa, Mamoru Nango, Masato Yamamoto
KEYWORDS:
DPPC-Chol Mixed Monolayer, Dropping Method, Surface Tension Measurement, Brewster Angle Microscopy, Fluorescence Microscopy, Condensation Effect
JOURNAL NAME:
Journal of Biophysical Chemistry,
Vol.7 No.4,
October
14,
2016
ABSTRACT: Morphology of dipalmitoyl phosphatidyl choline (DPPC)-cholesterol (Chol) mixed monolayer formed on water surface by dropping method was investigated using surface tension measurement (STm), Brewster angle microscopy (BAM), and fluorescence microscopy (FM). STm showed strong condensation effect of Chol in fluidic DPPC monolayer. Excess area (Sex) from mean mixing state of DPPC and Chol was about twice larger than that by general compression method in the range from xC = 0.2 to 0.4 (xC: mole fraction of Chol). BAM and FM images showed clearly that the fluidic DPPC monolayer changed to condensed rigid monolayer due to the condensation effect of Chol. At more than xC = 0.3 DPPC-Chol mixed monolayer changed to condensed state similar to the Chol monolayer. These results support previous reports by compression method that Chol molecule demonstrates the strong condensation effect to the fluidic monolayer and also indicate that dropping method enables to form unique monolayer on the water surface.