Indirect micromanipulation of single molecules in water-in-oil emulsion

Based on real-time observation and micromanipulation, analytical methods fo r single DNA molecules have been under development for some time. Precise m anipulation, however, is still difficult because single molecules are too s mall for conventional techniques. We have developed a chemical reaction sys tem that uses water droplets in oil as containers of materials. The water d roplets can be manipulated by optical force. The manipulation of the water droplets permits the fusion of two selected droplets. This process correspo nds to mixing of different samples. We designate this system as "w/o (water -in-oil emulsion) microreactor system", acid each droplet can be thought of as a "microreactor". In this system, single molecules can be manipulated r eadily, as a molecule can be contained in a mum-sized microreactor. The mic roreactor utilizes extremely small quantities of samples, therefore, reacti ons are rapid, as diffusion times in the microreactor are very short. The m anipulation technique of the microreactors based on optical force has been applied to induce fusion between microreactors loaded with DNA and YOYO, a fluorescent dye that binds to DNA. This fusion induced a rapid binding of Y OYO.