Isoguanine (2-oxo-6-amino-guanine, isoG) can form the higher-order self-pairing ionophore structures by regulating the concentration of metal ions. The metal ion coordinated isoG-tetrads adopt bowl-like shape with the metal ion located at the bottom of the bowl. The present study of the formation of the H-bonded octamers ((isoG(4) M+)2(;) M+ = Na+, K+) illustrates that the bowl-shaped isoG4-M+ complexes are able to form the extraordinary ball-shaped octamers (isoG(4)-M+)(2) H-bonded through the H(N6) and N7 sites. A moderate energy barrier predicted for the process of separating the ball-shaped octamer into two bowl-shaped tetrads and the unique structural features of the octamer suggests a possibility towards construction of the self-assembled isoG nanostructures. (C) 2007 Elsevier B.V. All rights reserved.