We have measured temperature-dependent (between 20 and 8 0 ° C) electrical conductivity and molecular structure (Raman spectroscopy) of DNA-lipid cast film. Our findings show that the conductivity is strongly influenced by premelting effects in the molecular structure starting near physiological temperatures ( ～ 4 0 ° C), prior to the global DNA denaturation. Most measurements reported in the last decade on the DNA conductivity are conducted at room temperatures and below [1]. If DNA is to become exploitable in microelectronics applications, however, its performance must be reliable at temperatures slightly above the room temperature due to the inevitable heating of electronic components. It is generally agreed that natural DNA molecules undergo a denaturation process at ？？ ？？ ？？ = 7 0 ～ 8 0 °C. Above this temperature, the double-stranded molecular conformation is destroyed, and consequently, the electrical conductivity is lost [2, 3]. According to numerous theoretical models [4, 5] even at physiological temperatures ( ～ 40°C), DNA experiences structural perturbations leading to local denaturations and/or “bubble-” type defect formations. The existence of “bubbles” [6, 7] as well as the temperature induced local perturbations at ？？ < ？？ ？？ ？？ , termed “premelting,” [8–12] has been confirmed experimentally, and the biological aspects of these local denaturations were discussed in a number of studies (see, e.g., [6]). Local deformations should cause breaking of a long-range order in the DNA structure (i.e., interruption of the parallel base-pair (bp) stackings) similar to an order breaking in solid bodies due to the dislocation introduction. However, their influence on conductivity has not been properly addressed until now. In this work, we present the temperature-dependent conductivity and structural evolution monitored through Raman spectroscopy measured on the DNA-lipid cast film between physiological and denaturation temperatures. These DNA-lipid films were previously studied by Nakayama et al. [2], where disappearance of conductivity above the denaturation temperature was reported. We observed a substantial reduction in the DNA conductivity due to premelting effects starting at temperature as low as 40°C, lending support to the theoretical inference on the importance of the long-range parallel bp stacking in DNA for the electrical conduction. Self-standing DNA-lipid cast films with thickness of about 60 microns were prepared according to the method described elsewhere [13]. Once the self-standing film is mechanically stretched, DNA molecules (natrual
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