tokens: Bivalent cations such as Mg2+ and Zn2+ differentially affect their binding to oligonucleotides which contain the HIV-enhancer domain .
folded_tokens: bivalent cations such as mg2+ and zn2+ differentially affect their binding to oligonucleotides which contain the hiv-enhancer domain .
labels: B-atom I-atom O O B-atom O B-atom O O O O O B-polynucleotide O O O B-DNA_domain_or_region I-DNA_domain_or_region O