Imaging and mechanical measurement of plant organelles by AFM

Takafumi Yamada, Hideo Arakawa, Takaharu Okajima, Takayoshi Shimada and Atsushi Ikai

Graduate School of Bioscience and Biotechnology, Tokyo Institute of Technology, Yokohama 226-8501, Japan

If an AFM cantilever was driven at its thermal vibration frequency of about 3 kHz, the oscillation amplitude could be kept large enough against the viscous drag of water and found suitable for imaging in tapping mode compared with the high frequency oscillation method conventionally used for imaging. We successfully applied this method with a soft cantilever to obtain clear images of photo-convertible plant organelles, namely, chloroplast and etioplast without causing damages to the sample surface, although the organella are soft and of a round shape. Alcian blue 8GX dye was found effective to immobilize organella on a glass surface for imaging purposes. Using an AFM, we also measured some mechanical properties of the above mentioned organelles. We will discuss the observed differences of mechanical properties of etioplast and those of chloroplast based on their inner- structures.