The infrared spectrum and structure of the type I complex of silver and DNA

Abstract

Infrared spectroscopy was used to study films of the type I complex of Ag+ and DNA as a function of hydration with the following conclusions. (1) Ag+ binds to guanine residues but not to cytosine or thymine residues. (2) Cytosine becomes protonated as Ag+ binds to guanine. (These conclusions confirm previous models.) (3) The type I complex remains in the B family of structures with slight modifications of the sugar-phosphate geometry. (4) This modified B structure remains stable at lower values of hydration for which pure DNA is in the A form. (5) Binding of Ag+ to PO2 O-P-O or the deoxyribose oxygen is excluded. © 1985 IRL Press Limited.