Studies on interactions between immobilized lysine residues and oligomers of thymidylic and deoxyadenylic acids

Two groups of crosslinked polyacrylic gels with immobilized lysine and lysine peptides (Lys)5 and (Lys)5-Pro have been used as models for the chromatographic investigation of lysine-peptide-oligonucleotide interactions. One group carries carboxylic groups in addition to the peptide residues in the gel matrix; the other gel type contains no such carboxylic groups in the gel matrix. Nucleotides of the series (dT)2-5, p(dT)1-4, p(dT)1-4p, (dA)2-5, p(dA)1-5 and p(dA)1-4p were chromatographed on these gels under various conditions in an aqueous buffer. On the gels of the first group the nucleotides were retarded only slightly, the positive charges of the epsilon-amino groups being compensated partially or totally by the negatively charged carboxyl groups of the polymer matrix. On the gels of the second group, however, the oligonucleotides underwent specific interactions. These interactions were based primarily upon electrostatic forces between the positively charged epsilon-amino groups of the immobilized peptides and the negatively charged phosphate groups of the oligonucleotides. Our results indicate that, in addition to the electrostatic interaction, the conformation plays a crucial role. We explain the selectivity of the interaction with a conformation-fit mechanism. The origin of this mechanism, which creates specific interactions from unspecific forces, is discussed.