Flat hydrogel substrate for atomic force microscopy to observe liposomes and lipid membranes |
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Authors: | Akihiko Takagi Hitomi Hokonohara Tomoji Kawai |
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Institution: | (1) The Institute of Physical and Chemical Research (RIKEN), 2-1 Hirosawa, Wako, Saitama 351-0198, Japan;(2) The Institute of Scientific and Industrial Research (ISIR), Osaka University, 8-1 Mihogaoka, Ibaraki, 564-0047 Osaka, Japan; |
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Abstract: | In order to avoid denaturation of biomolecules due to strong adsorption on solid surfaces, a soft substrate has to be used
for atomic force microscopy (AFM) observation. We propose a hydrophilic agarose gel surface as a soft substrate for AFM to
observe liposomes and lipid membranes. Although our simple method does not require any delicate control at the molecular level,
an agarose gel surface can be simply flattened to 0.3 nm in roughness using an atomically flat solid surface during gelation.
The AFM images revealed that liposomes were unruptured on the gel surface at low liposome density, whereas an unruptured state
was difficult to obtain on a solid surface like mica. This indicates that the weak interaction between the liposome and the
soft surface inhibits the liposome from rupturing, and also that the surface rougher than the solid surface prevents lateral
diffusion of the liposomes along the surface to be fused. Increasing the liposome density resulted in a lipid membrane at
various thicknesses forming on the hydrogel surface by the fusion and rupture of liposomes. Using the soft substrate, it can
be expected to promote investigations of structures and functions of biomolecules at the nanometer scale under physiological
conditions with AFM. |
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