ydrogen-bonding interactions are crucial to the stabilization of the DNA double helix. Adenine is hydrogen bonded to thymine via two hydrogen bonds, whereas guanine and cytosine are hydrogen bonded through three hydrogen bonds. Thus, poly-nucleic acids containing adenine-thymine pairs are expected to have different hydrogen bonding interactions than poly-nucleic acids containing guanine-cytosine pairs. The vibrational modes associated with hydrogen bonds fall in the far-infrared region (150-250 cm-1). Thus, a comparison of the far infrared spectra of poly-dAdT versus poly-dGdC provides a method for studying hydrogen-bonding interactions in DNA. We have grown films of Hpoly-(dAdT), poly-(dA) poly-(dT), poly-(dGdC), and poly-(dG) poly-(dC) Hon polyethylene disks and determined their far infrared spectra from H10 - 295 K. In poly-(dAdT), we observe a single, intense band at 168 Hcm-1, which shifts to 178 cm-1 at cryogenic temperatures (40 K). In Hpoly-(dGdC), we observe two intense bands in the far infrared at room Htemperature: 96 and 162 cm-1. The intensity of the 96 cm-1 mode Hdecreases dramatically at 10 K and the peak at 162 cm-1 shifts to 166 Hcm-1 at 10 K. We plan to continue our studies on poly-nucleic acids by Hgrowing films under different conditions, such as in the presence of HD2O and varying humidity conditions. D2O is expected to shift the Hfrequency of hydrogen-bonding interactions and humidity variations Hmake it possible to generate different helical conditions such as B-Hversus A-DNA.
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