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 a ≈1 MHz, >1×10⁶ V/m field, by which the DNA strands are stretched straight along field lines and positioned onto electrode edges. In the present work they discuss some applications 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 immobilization onto a conducting substrate for observations with scanning tunneling microscopy and anchoring onto a substrate only at the two ends of DNA using a 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 DNAs are cut by laser beam for successive sequencing. A method for obtaining unidirectionally oriented DNAs is developed