Optical Trapping of Single DNA Molecule Complexed with Cationic Surfactant

Yuichi Yamasaki¹, Ken Hirano², Keisuke Morishima³, Akira Mizuno², Fumihito Arai³ and Kenichi Yoshikawa⁴

¹Graduate School of Human Informatics, Nagoya University, Nagoya 464-0814, Japan
²Department of Ecological Engineering, Toyohashi University of Technology, Toyohashi, Aichi 441-8580, Japan
³Department of Micro System Engineering, Faculty of Engineering, Nagoya University, Nagoya 464-0814, Japan
⁴Department of Physics, Faculty of Science, Kyoto University, Kyoto 606-8502, Japan

(Received November 13, 1998; Accepted January 6, 1999)

Keywords: Giant Duplex DNA, Coil-Globule Transition, Laser Manipulation, Fluorescence Microscopy, Optical Tweezers

Abstract. Optical trapping with laser light (Nd:YAG; 1064 nm) is found to be applicable for the manipulation of single DNA chains; T4DNA (166 kbp), complexed with a cationic surfactant, cetyltrimethylammonium bromide (CTAB). Although there have been increasing number of studies on the optical manipulation on individual macromolecules, most of them are the experiments for the polymer molecule attached to mm-sized particle. In the present paper, we will show that the compact globular DNA complexed with CTAB is effectively trapped with the laser beam. With the trapping, intrachain fluctuation on single DNA becomes to be observed more apparently, in comparison to free DNA exhibiting translational Brownian motion. Actually, the coexistence between collapsed and elongated parts in a single DNA has been visualized clearly.