DNA INTERACTION WITH MANGANESE IONS STUDIED BY INFRARED-SPECTROSCOPY

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 them (n = 8). The shift of the absorption band of sorbed water to lower frequences for the DNA-Mn2+ complex may indicate tighter water binding. The Mn2+ ions were found to bind with DNA phosphates and guanine, forming chelates of the N(7)-Mn2+-O(6) type.