Characterization of DNA structures by infrared spectroscopy: double helical forms of poly(dG-dC)•poly(dG-dC), poly(dD8G-dC)•poly(dD8G-dC), and poly(dG-dm5C)•poly(dG-dm5C)

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Abstract
Infrared spectroscopy in the 1750–700 cm−1 region is used to characterize the right- and left-handed helices of poly(dG-dC)•poly(dG-dC) with sodium counterions. The use of polymers selectively deuterated on the C8 of guanines and methylated on the C5 of cytosines allows us to propose explanations for several spectroscopic modifications which occur under the B → Z transition. Similar substitutions on nucleosides and nucleotides are used so as to assign base absorptions in poly(dG-dC)•poly(dG-dC). A set of ir bands characteristic of DNA conformations, which can be used in studies of interactions with this polynucleotide and to identify the left handed Z conformation in more complex systems, is proposed.