Ca2+-Induced Effect on Mechanical Properties of Sulfatide-Incorporated Vesicles
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The Ca2+-induced effect on the nanomechanical properties of vesicles prepared at a different ratio of dipalmitoylphosphatidylcholine (DPPC)/sulfatide was studied using atomic force microscope (AFM) on a mica surface. Vesicles were prepared by extrusion and adsorbed on the mica surface. The forces, measured between an AFM tip and the vesicle, showed that the breakthrough of the tip into the vesicles occurred two times. Force data prior to the first breakthrough were fitted well with the Hertzian model to estimate Young’s modulus and bending modulus of the vesicles. Sulfatide incorporation led to a decrease of around 90% in Young’s modulus and bending modulus of the vesicles due to the hydration of the headgroups, while the addition of Ca2+ induced dehydration to recover the properties. The change of the physical properties seems to be attributed to the headgroup packing order of the vesicles, which is determined by the interference with the hydration shell.
KeywordsBiophysical techniques in membrane research Biophysics Measurement Membrane assembly Membrane biophysics
This research was supported by the Basic Science Research Program through the National Research Foundation of Korea funded by the Ministry of Education, Science and Technology (2010-0010097). We thank all of the members of the Department of Chemical Engineering at Seoul National University of Science and Technology for help and valuable discussions. We thank Prof. D. J. Ahn, Dr. G. S. Lee, Mr. H. Choi and Mr. C. S. Choi at Korea University for valuable help.
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