In this work, we have studied a hemin-DNA complex in relation to ribozymes/deoxyribozymes by using electrochemical techniques. We have also studied the gaseous ligand binding property of the complex, where oxygen and nitric oxide are chosen as the ligands. It is found that the complex can accept nitric oxide and form a relatively stable ligand binding complex, but it is not ready to accept oxygen due to a DNA barrier. A better understanding of this complex may contribute to the knowledge of primitive lives. (c) 2008 Elsevier Ltd. All rights reserved.