Inter-strand C - H...O hydrogen bonds stabilizing four-stranded intercalated molecules: Stereoelectronic effects of O4' in cytosine-rich DNA

摘要

DNA fragments with stretches of cytosine residues can fold into four-stranded structures in which two parallel duplexes, held together by hemiprotonated cytosine cytosine (C.C~+) base pairs, intercalate into each other with opposite polarity. The structural details of this intercalated DNA quadruplex have been assessed by solution NMR and single crystal x-ray diffraction studies of cytosine- rich sequences, including those present in metazoan telomeres.