Applications of electrostatic stretch-and-positioning of DNA

The authors have previously reported that the electrostatic orientation and the dielectrophoresis (DEP) of DNA occur under ≈1 MHz, >1×10⁶ V/m field, by which DNA strands are stretched straight along field lines and positioned onto electrode edges. This paper presents some application of this stretch-and-positioning method to genetic engineering. It is shown that the DNA size distribution, as well as the activities of nuclease, can be determined by the measurement of the apparent length of stretched DNA. Several methods are developed to immobilize stretched DNA onto a substrate, including: (1) immobilization onto a conducting substrate for observations with the scanning tunneling microscopy, (2) anchoring onto a substrate only at both ends of the DNA using special electrode configuration, and/or molecular binding between avidin and biotin. The DNA can be held without contact to the substrate in the latter method, so that it does not cause steric hindrances to the DNA-binding enzymes. A novel fluid integrated circuit (FIC) device is proposed in which stretched DNA is cut by laser beam for the successive sequencing. A method to obtain unidirectionally oriented DNA is developed. The spatial resolution, and the small number of molecules required, are the advantages of the assays and measurements using electrostatic DNA manipulations over conventional biochemical methods. It is hoped that the methods may open a way to a novel category of “molecular biochemistry with spatial resolution.”