The interaction of DNA (calf thymus) with hemin was studied by means of cyclic voltammetry (CV) in a salt bridge supported bilayer lipid membrane (sb-BLM) system. Sb-BLM was modified with lauric acid (LA) dissolved in the membrane forming solution, then hemin molecules in electrolyte could also be embedded into the BLM by electrostatic interaction between hemin and LA. Hemin showed a well-defined CV behavior. The cathodic peak current (I-Pc,) of hemin decreased in the presence of DNA, which is consistent with the results of decreasing hemin concentration and illustrates the existence of interaction between hemin and DNA. The interacting mechanism was studied. The effect of pH on the interaction was also considered. The I-Pc of hemin decreases in proportion to the DNA concentration from 8.44 x 10(-5) to 6.75 x 10(-4) mol l(-1), which provided a possibility of detecting DNA with a natural biological substance in a biomimetic membrane system. (C) 2001 Elsevier Science Ltd. All rights reserved.