ABSTRACT
By applying infrared spectroscopy for dry DNA, we can conveniently
obtain information on conformation, content of hydrated water
molecules, and hydration structure. In the regulated base-pair
sequence of poly(dG)–poly(dC) double strand, the characteristic
absorption band emerges at 1400 cm−1 in contrast to poly(dA)– poly(dT) and natural DNA. Through the spectral difference from Li-
DNA and Na-DNA with monovalent counterions, the intercalation of
divalent and trivalent metallic counterions into natural DNA yields
a novel N-M bonding in the base molecules. Around the negatively charged phosphate group, disappearance of such counterions is
found to induce anisotropy against the electric dipole and to
drastically change the hydration structure.
