Rutins, a kind of flavonoid glycoside, showed different absorption and fluorescence spectral characteristics when bound to blunt-end stacked and interlocked extended G-quadruplexes. Further H-1 NMR spectra showed these two extended G-quadruplexes bound with rutins in different manners: after binding, the blunt-end stacked extended G-quadruplexes were decomposed to monomers, and the interlocked extended G-quadruplexes did not change. Based on these spectral features, one may expect the usage of rutins in recognizing different structural extended G-quadruplexes and regulating the ratio between blunt-end stacked extended G-quadruplexes and monomers. (c) 2006 Elsevier Inc. All rights reserved.