Seminar: Direct Observation of Tube-Like Motion of Single DNA Molecules Strongly Confined in Nanoslits

Prof. Chiafu Chou
Institute of Physics, Genomics Research Center
Research Center for Applied Sciences, Academia Sinica
Taipei 11529, Taiwan

Tube-like motion of fluorescently labeled T4-DNA (148 kbp) in fused silica nanoslits of 13 and 25 nm height was observed by fluorescence microscopy. Driven by a pulsed electrical field, two free ends of the DNA straddle over two micro/nano interfaces and form a single molecule DNA tug-of-war (TOW) scenario due to the entropic recoiling forces. The molecule was then stretched and constrained to a tube-like region in a nanoslit. At the end of TOW, the polymer retracted from one micro-region to the other through the nanoslit, while closely followed a path of its initial contour. The tube-like motion observed here is surprising as it normally occurs in a 2D-confined environments. We analyzed the tube diameter and the entropic recoiling force of various slit heights. Our experiments show that the tube-like motion may be explained by both the strong confinement effect and the interaction between DNA and surface-passivating polymer brush in the nanoslits. Our findings may find applications in single molecule analysis, such as DNA mapping, sequencing and nanobiotechnology.

March 26, 2012 at 11:00 in the IENI meeting room