Quadruplexes of human telomere dG3(TTAG3)3 sequences containing guanine abasic sites

► Loss of a guanine base does not hinder the formation of G-quadruplex of human telomere sequence. ► Each depurination strongly destabilizes the quadruplex of dG3(TTAG3)3 in NaCl and KCl. ► Conformational change of the abasic analogs of dG3(TTAG3)3 is inhibited in KCl. ► The effects abasic sites may affect telomere-end structures in vivo.