Lanthanide ion luminescence as a probe of DNA structure. 2. Non- guanine-containing oligomers and nucleotides.

Oligo(dC)8, oligo(dA)8, and oligo(dT)8 as well as d-CMP, d-AMP, and d-TMP, when complexed to Eu(3+), possess two classes of Eu(3+) binding environment. The binding environments consist of two classes, tight sites which coordinate two H2O molecules, and weaker sites which coordinate six or seven, analogous to the previously studied guanine-containing molecules. It is inferred that the tight class of Eu(3+) ion site observed with these oligomers and nucleotides corresponds to dimeric or polymeric structures. Comparison of the results for the guanine and non-guanine containing oligomers suggests that Eu(3+) possibly coordinates base nitrogen atoms in the former and in an outer sphere mode (hydrogen bonding via the H2O molecules coordinated to Eu(3+)) in the species examined here.