Analytical Sciences

A Nanodiamond-peptide Bioconjugate for Fluorescence and ODMR Microscopy of a Single Actin Filament

Takuya GENJO,*1 Shingo SOTOMA,*1,*2 Ryotaro TANABE,*1 Ryuji IGARASHI,*1,*3 and Masahiro SHIRAKAWA*1,*4,*5

*1 Department of Molecular Engineering, Graduate School of Engineering, Kyoto University, Nishikyo, Kyoto 615-8510, Japan
*2 Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei 106, Taiwan
*3 PRESTO, Japan Science and Technology Agency, Kawaguchi 332-0012, Japan
*4 Institute for Integrated Cell-Material Sciences (WPI-iCeMS), Kyoto University, Yoshida-Honmachi, Sakyo, Kyoto 606-8501, Japan
*5 CREST, 4-1-8 Honcho, Kawaguchi, Saitama 332-0012, Japan

Recently, the importance of conformational changes in actin filaments induced by mechanical stimulation of a cell has been increasingly recognized, especially in terms of mechanobiology. Despite its fundamental importance, however, long-term observation of a single actin filament by fluorescent microscopy has been difficult because of the low photostability of traditional fluorescent molecules. This paper reports a novel molecular labeling system for actin filaments using fluorescent nanodiamond (ND) particles harboring nitrogen-vacancy centers; ND has flexible chemical modifiability, extremely high photostability and biocompatibility, and provides a variety of physical information quantitatively via optically detected magnetic resonance (ODMR) measurements. We performed the chemical surface modification of an ND with the actin filament-specific binding peptide Lifeact and observed colocalization of pure Lifeact-modified ND and actin filaments by the ODMR selective imaging protocol, suggesting the capability of long-term observation and quantitative analysis of a single molecule by using an ND particle.

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