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Mechanism and Dynamics of Breakage of Fluorescent Microtubules

Honglian Guo ^*, Chunhua Xu ^*, Chunxiang Liu , E. Qu ^*, Ming Yuan , Zhaolin Li ^*, Bingying Cheng ^* and Daozhong Zhang ^*

^* Optical Physics Laboratory, Institute of Physics, Chinese Academy of Sciences, Beijing 100080, China; Department of Physics, Shandong Normal University, Jinan, Shandong 250014, China; and State Key Laboratory of Plant Physiology and Biochemistry; College of Biological Sciences, China Agricultural University, Beijing 100094, China

Correspondence: Address reprint requests to Honglian Guo, Optical Physics Laboratory, Institute of Physics, Chinese Academy of Sciences, Beijing 100080, China. Tel.: 86-10-82649340; Fax: 86-10-82649451; E-mail: hlguo{at}aphy.iphy.ac.cn.

The breakage of fluorescence-labeled microtubules under irradiation of excitation light is found in our experiments. Its mechanism is studied. The results indicate that free radicals are the main reason for the photosensitive breakage. Furthermore, the mechanical properties of the microtubules are probed with a dual-optical tweezers system. It is found that the fluorescence-labeled microtubules are much easier to extend compared with those without fluorescence. Such microtubules can be extended by 30%, and the force for breaking them up is only several piconewtons. In addition, we find that the breakup of the protofilaments is not simultaneous but step-by-step, which further confirms that the interaction between protofilaments is fairly weak.