Title: Sequence and Length Dependence of the Conductivity of Individual DNA Duplexes and Applications in Protein Detection
Description: This thesis introduces a new type of DNA-based molecular electronics that is composed of an individual DNA duplex bridging a single-walled carbon nanotube (SWCNT) gap. Using this type of device, we have been able to measure the conductivity of DNA directly, and have successfully assessed its dependence on DNA sequence and length. Our approach to measuring DNA conductivity has a number of advantages over previous methods in that our devices possess single DNA duplex bridging the gap, well-defined DNA-electrode junctions, and preserve the DNA's native conformation. We apply this type of device to selectively and sensitively detect a methyltransferase, whose function is to catalyze the addition of a methyl group on the cytosine base of 5'-GC-3' sequences. This thesis is comprised of four chapters. Chapter 1 discusses previous research on DNA-mediated charge transport (CT) and its application to protein detection. This chapter also highlights the advantages of using our method to study DNA-medicated CT, and illustrates its potential in biosensing.

Chapter 2 includes the details of the fabrication procedures of the single molecule DNA device. This fabrication procedure outlines concrete guidelines to manufacture single molecule electronics based on SWCNT electrodes. Chapter 3 details the studies on the conductivity of individual DNA duplexes using this type of DNA-SWCNT device. Sequence dependence and length dependence of DNA conductivity are specifically addressed in this chapter. Chapter 4 reviews the application of this type of device to sensitively and selectively detect DNA-binding proteins such as methyltransferase M.SssI. This study presents a prototype of single-molecule-level electronic biosensors.