DNA complexes with Mn2+ ions in films were studied by IR spectroscopy
at varying relative humidity and ion concentration ([Mn2+]/[p] = 0.4-1
.0). A substantially larger number of sorbed water molecules (n = 14)
was required for the DNA transition into a double-helical conformation
(preferentially B form) in the presence of Mn2+ ions than without the
m (n = 8). The shift of the absorption band of sorbed water to lower f
requences for the DNA-Mn2+ complex may indicate tighter water binding.
The Mn2+ ions were found to bind with DNA phosphates and guanine, for
ming chelates of the N(7)-Mn2+-O(6) type.