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Summary: 1
Base Pair Stacking in Aligned Films of DNA-lipid complex
C.Y. Yang, D. Moses and A.J. Heeger
In addition to its obvious and well-known importance to biology, deoxyribonucleic acid
(DNA), as a one-dimensional macromolecule, has attracted interest as a material for use in
functional mesoscopic electronic devices and in molecular computing. The -electron overlap
between the base pairs within the double helix suggests that the stacked base pairs might be a
one-dimensional pathway for electronic charge transport. However, although the transport
properties of DNA have been studied, a wide range of results have been reported with properties
spaning the full range from insulating to semiconducting to metallic and even to superconducting
behavior. Thus, the concept of DNA as an electronic material is uncertain and controversial.
The concept of DNA as an electronic material requires aligned DNA helices and good -
electron overlap between bases along the helix axis. We have developed aligned films of a DNA-
lipid complex that satisfy both these criteria: aligned helices separated by 4.1 nm with excellent
base pair stacking.
From X-ray diffraction studies of tensile drawn films under different conditions (dry, wet,
and at low temperature), we find that the base pair separation spacings within a DNA helix are
0.41 nm when the sample is dried in air at 50% relative humidity and 0.34 nm in aqueous
environment at room temperature (RT). This implies that hydration of DNA causes the bases to
rotate from edge to planar stacking with improved -electron overlap between bases along the
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