Multiplicity of cadmium binding sites in nucleotides: X-ray evidence for the involvement of O2' and O3' as well as phosphate and N7 in inosine 5'-monophosphate.

Single-crystal X-ray methods have been used to characterize a hydrated polymeric cadmium derivative of inosine 5'-monophosphate. In the structure there are two independent cadmium atoms, one of which binds to two ribose oxygen atoms, an N7 position on a base, and to three water molecules. The second metal atom binds to a phosphate oxygen, three water molecules, and to two N7 atoms, which are in cis-positions. For these last; the Cd-N bonds are appreciably out of the planes of the hypoxanthine bases so that the angle between these planes is only 31.4 degrees.