Abstract
The recent application of histidine–agarose affinity supports in plasmid purification takes advantage of the biorecognition of nucleic acid bases by the histidine ligand. This consideration prompted the need for better understanding the interactions involved in affinity chromatography of plasmid DNA with the histidine–agarose support. In this work, we used synthetic homo‐deoxyoligonucleotides with different sizes (1–30 nucleotides long), to explore the effect of several conditions like hydrophobic character of the individual bases, presence of secondary structures, temperature, pH and salt concentration on the mechanism of retention of nucleic acids to histidine–agarose support. One of the most striking results shows that histidine interacts preferentially with guanine, and the presence of secondary structures on polyA and polyG oligonucleotides has a significant influence on retention. Otherwise, the temperature manipulation has not shown a direct influence on oligonucleotide retention, only inducing conformational changes on secondary structures. Overall, the results obtained provide valuable information for the future development and implementation of histidine and other amino acids as ligands in chromatography for the purification of plasmid DNA and other nucleic acids, by improving the knowledge of the interactions involved as well as of the parameters influencing the retention. Copyright © 2009 John Wiley & Sons, Ltd.