Deoxyribonucleic acid (DNA) molecules in water entangle together and form agglomerated spongy spherical structure. However, when the multiwall carbon nanotubes (MWNTs) are added to the solution, DNA effectively interacts with MNVNTs and disentangled DNA molecules immobilize at the surface of MWNT. Such phenomena are identified by the tapping mode atomic force microscopy (AFM), which clearly indicates the string-like DNA molecular images. On the other hand. the agglomerated form of DNA cannot be disentangled on the highly oriented pyrolytic graphite (HOPG) surface. These facts clearly indicate that the curvature of MWNT plays an important role for the interaction with DNA molecules. (c) 2005 Elsevier B.V. All rights reserved.